European Journal of Pharmaceutics and Biopharmaceutics (v.78, #3)

APV Diary (I).

Standardization of fluorine-18 manufacturing processes: New scientific challenges for PET by Ole K. Hjelstuen; Anders Svadberg; Dag E. Olberg; Mark Rosser (307-313).
In [18F]fluoride chemistry, the minute amounts of radioactivity taking part in a typical radiolabeling reaction as in the attached flow-chart are easily outnumbered by other reactants. Surface areas become comparably larger and more influential than in standard fluorine chemistry, while leachables, extractables and other components that normally are considered small impurities can have a considerable influence on the efficiency of the reaction. There are still areas of limited knowledge in the fundamental [18F]fluoride chemistry and there is a number of pharmaceutical factors that could influence several steps and the final outcome of the 18F-radiosynthesis.In [18F]fluoride chemistry, the minute amounts of radioactivity taking part in a radiolabeling reaction are easily outnumbered by other reactants. Surface areas become comparably larger and more influential than in standard fluorine chemistry, while leachables, extractables, and other components that normally are considered small impurities can have a considerable influence on the efficiency of the reaction. A number of techniques exist to give sufficient 18F-tracer for a study in a pre-clinical or clinical system, but the chemical and pharmaceutical understanding has significant gaps when it comes to scaling up or making the reaction more efficient. Automation and standardization of [18F]fluoride PET tracers is a prerequisite for reproducible manufacturing across multiple PET centers. So far, large-scale, multi-site manufacture has been established only for [18F]FDG, but several new tracers are emerging. In general terms, this transition from small- to large-scale production has disclosed several scientific challenges that need to be addressed. There are still areas of limited knowledge in the fundamental [18F]fluoride chemistry. The role of pharmaceutical factors that could influence the 18F-radiosynthesis and the gaps in precise chemistry knowledge are discussed in this review based on a normal synthesis pattern.
Keywords: 18F-chemistry; PET; Automation; Glass/plastic leachables; Standardization;

Antitumoral and antimetastatic effect of antiangiogenic plasmids in B16 melanoma: Higher efficiency of the recombinant disintegrin domain of ADAM 15 by Liévin Daugimont; Gaelle Vandermeulen; Florence Defresne; Caroline Bouzin; Lluis M. Mir; Céline Bouquet; Olivier Feron; Véronique Préat (314-319).
Intratumoral electrotransfer of three antiangiogenic plasmids inhibits tumor growth and metastasis of B16F10 melanoma.Despite the discovery of novel inhibitors of tumor angiogenesis, protein-based antiangiogenic cancer therapy suffers some limitations that antiangiogenic gene therapy could overcome. We investigated whether intra-tumoral electrotransfer of three angiogenic plasmids could inhibit tumor growth and metastasis.Plasmids encoding recombinant disintegrin domain of ADAM-15 (RDD), thrombospondin 1 (TSP-1), and the soluble isoform of the VEGF receptor 1 (sFlt-1) were injected into B16F10 melanoma-bearing C57BL/6 mice followed by electroporation. Tumor volume was measured daily using a digital caliper. Metastasis was monitored by in vivo bioluminescence after surgical removal of the primary luciferase-encoding B16F10 tumor 5 days after intra-tumoral electrotransfer. Markers of vascularization and cell proliferation were quantified by immunohistochemistry.Intra-tumoral electrotransfer of the antiangiogenic plasmids induced a significant inhibition of tumor growth, doubling of mean survival time and long-term survivors (∼40% vs 0% in control). When the tumor was removed by surgery after intra-tumoral plasmid electrotransfer, a significant decrease in tumor metastasis was observed leading to long-term tumor-free survival especially after treatment with pRDD plasmid (84% vs 0% in control). Unlike pTSP-1 and psFlt-1, pRDD significantly decreased cell proliferation in B16F10 primary tumors which express αvβ3 and α5β1 integrins. No effect of antiangiogenic plasmid electrotransfer on normal skin blood flow was detected.The intra-tumoral electrotransfer of the three antiangiogenic plasmids is a promising method for the treatment of melanoma. The plasmid encoding RDD seems to be particularly effective due to its direct antitumoral activity combined with angiogenesis suppression, and its marked inhibition of metastasis.
Keywords: Antiangiogenic plasmid; Melanoma; Electroporation; Disintegrin domain of ADAM 15;

Liver-specific gene therapy of hepatocellular carcinoma by targeting human telomerase reverse transcriptase with pegylated immuno-lipopolyplexes by Yurong Hu; Yingying Shen; Baofang Ji; Shasha Yin; Xueling Ren; Tingting Chen; Yue Ma; Zhenzhong Zhang; Yun Zhang (320-325).
pApoAl-shTERT: shRNA expression plasmid against hTERT under the control of the liver-specific promoter ApoAl. pApoAl-GFP: GFP expression plasmid under the control of ApoAl promoter. PILP: Pegylated immuno-lipopolyplexes.The purpose of this study is to explore the possibility and feasibility of liver-specific gene therapy. A shRNA expression plasmid against human telomerase reverse transcriptase (hTERT) was constructed under the control of liver-specific promoter apolipoprotein A-I (ApoAI), designated as pApoAI-shTERT, and its liver-specific cytotoxicity and inhibition of telomerase activity were first evaluated in different cell lines, and its therapeutic effect was further studied in SMMC-7721 human liver tumor-bearing mice in vivo. The results showed that compared to pU6-shTERT, a shRNA expression plasmid against hTERT under the control of U6 promoter, pApoAI-shTERT only significantly diminished the cell viability in the telomerase positive hepatocarcinoma cells and showed no cytotoxicity in the telomerase negative cell lines as well as in the telomerase positive cell line of non-liver origin. Besides, pApoAI-shTERT only significantly reduced telomerase activity in the telomerase positive cell lines of liver origin. Intravenous administration of pegylated immuno-lipopolyplexes (PILP) formulated green fluorescent protein (GFP) expression plasmid under the control of ApoAI into liver tumor-bearing mice resulted in restricted GFP expression in liver and liver tumor. The treatment of pApoAI-shTERT formulated as PILP caused a 56% increase in the life span of SMMC-7721 tumor-bearing mice in vivo relative to the control, which was in agreement with the reduced tumor size and down-regulated hTERT mRNA level in the tumors. We conclude that the vector pApoAI-shTERT was able to cause liver-specific and hTERT target-specific cytotoxicity, and utilizing PILP to deliver pApoAI-shTERT is a promising strategy for liver-specific gene therapy.
Keywords: hTERT; RNA interference; Hepatocellular carcinoma; Pegylated immuno-lipopolyplexes; Apolipoprotein A-I promoter;

Novel cationic lipids possessing protonated cyclen and imidazolium salt for gene delivery by Qing-Dong Huang; Wen-Jing Ou; Hong Chen; Zhi-Hua Feng; Jing-Yi Wang; Ji Zhang; Wen Zhu; Xiao-Qi Yu (326-335).
Two novel protonated cyclen and imidazolium salt-containing cationic lipids have been designed and synthesized for gene delivery.In this study, two novel protonated cyclen and imidazolium salt-containing cationic lipids differing only in their hydrophobic region (cholesterol or diosgenin) have been designed and synthesized for gene delivery. Cationic liposomes were easily prepared from each of these lipids individually or from the mixtures of each cationic lipid and dioleoylphosphatidyl ethanolamine (DOPE). Several studies including DLS, gel retardation assay, ethidium bromide intercalation assay, and TEM demonstrated that these amphiphilic molecules are able to bind and compact DNA into nanometer particles that could be used as non-viral gene delivery agents. Our results from in vitro transfection showed that in association with DOPE, two cationic lipids can induce effective gene transfection in HEK293 cells. Furthermore, the gene transfection efficiencies of two cationic lipids were dramatically increased in the presence of calcium ion (Ca2+). It is notable that the gene transfection abilities of two cationic lipids were maintained in the presence of 10% serum. Besides, different cytotoxicity was found for two lipoplexes. This study demonstrates that the title cationic lipids have large potential to be efficient non-viral gene vector.
Keywords: Gene therapy; Gene delivery; Cationic liposome; Cyclen; Imidazolium salt; Calcium ion;

Layer-by-layer assembly of poly(l-glutamic acid)/chitosan microcapsules for high loading and sustained release of 5-fluorouracil by Shifeng Yan; Jie Zhu; Zhichun Wang; Jingbo Yin; Yanzhen Zheng; Xuesi Chen (336-345).
The poly(l-glutamic acid)/chitosan (PLGA/CS) microcapsules prepared by layer-by-layer assembly technique show high loading capacity of hydrophilic anticancer drug 5-fluorouracil (5-FU) by simply soaking in 5-FU solution. Also prolonged 5-FU release is achieved from PLGA/CS microcapsules, in contrast to burst release of bare 5-FU.Hollow polyelectrolyte microcapsules based on poly(l-glutamic acid) (PLGA) and chitosan (CS) with opposite charges were fabricated by layer-by-layer (LbL) assembly technique using melamine formaldehyde (MF) microparticles as sacrificial templates. The LbL assembly of polyelectrolytes and the resultant PLGA/CS microcapsules were characterized. A hydrophilic anticancer drug, 5-fluorouracil (5-FU), was chosen to investigate the loading and release properties of the microcapsules. The PLGA/CS microcapsules show high loading capacity of 5-FU under conditions of high drug concentration and salt adding. The high loading can be ascribed to spontaneous deposition of 5-FU induced by hydrogen bonding between 5-FU and PLGA/CS microcapsules. The PLGA/CS microcapsules show sustained release behavior. The release rate of 5-FU drastically slows down after loading in PLGA/CS microcapsules. The 5-FU release from PLGA/CS microcapsules can be best described using Ritger–Peppas or Baker–Londale models, indicating the diffusion mechanism of 5-FU release from the PLGA/CS microcapsules. In vitro cytotoxicity evaluation by the MTT assay shows good cell viability over the entire concentration range of PLGA/CS microcapsules. Therefore, the novel PLGA/CS microcapsules are expected to find application in drug delivery systems because of the properties of biodegradability, high loading, sustained release and cell compatibility.
Keywords: Layer-by-layer self-assembly; Poly(l-glutamic acid); Chitosan; 5-Fluorouracil; Drug delivery systems;

Drug-carrier/hydrogel scaffold for controlled growth of cells by Lan Wei; Jiaping Lin; Chunhua Cai; Zhengdong Fang; Weiguo Fu (346-354).
VEGF165 (encourage cell growth) shows a short-term release, while PTX (inhibit cell growth) shows a long-term release from the drug-carrier/hydrogel scaffold. The constructed scaffold can encourage the fast growth of cells in the early period and inhibit the growth of cells in late period.In this work, a novel functional drug-carrier/hydrogel scaffold was prepared to control the growth of cells for tissue engineering. The drug-carrier/hydrogel scaffold was constructed from a micelle/Ca-alginate microparticles (Alg-MPs)/poly(vinyl alcohol) (PVA) hydrogel composite. In such a system, paclitaxel (PTX) is encapsulated in the micelles formed by poly(l-glutamic acid)-b-poly(propylene oxide)-b-poly(l-glutamic acid) (GPG), while human vascular endothelial growth factor-165 (VEGF165) is loaded in the Alg-MPs. The designed function of this scaffold is to encourage the fast growth of cells such as endothelial cells (ECs) in the early period to reduce the rejection and inhibit the growth of cells such as smooth muscle cells (SMCs) in late period to prevent the vascular intimal hyperplasia. The effect of VEGF165 is to encourage the growth of ECs, while PTX is used to inhibit the growth of smooth muscle cells (SMCs). Structure characterizations show that the drug carriers are well dispersed in the PVA hydrogel. Independent release behaviors of the two drugs are observed. VEGF165 shows a short-term release behavior, while PTX shows a long-term release behavior from the drug-carrier/hydrogel scaffolds. Further study shows a controllable cell growth behavior on this functional drug-carrier/hydrogel scaffold via the MTT assay.
Keywords: Scaffold; Drug delivery; Hydrogel; Micelle; Alginate;

An oral oligonucleotide delivery system based on a thiolated polymer: Development and in vitro evaluation by Ronny Martien; Herbert Hoyer; Glen Perera; Andreas Bernkop Schnürch (355-360).
Polycarbophil-cysteine potently inhibits nucleolytic degradation of oligonucleotides and significantly enhances their absorption across intestinal epithelia.The purpose of this study was to develop and evaluate an oral oligonucleotide delivery system based on a thiolated polymer/reduced glutathione (GSH) system providing a protective effect toward nucleases and permeation enhancement. A polycarbophil–cysteine conjugate (PCP–Cys) was synthesized. Enzymatic degradation of a model oligonucleotide by DNase I and within freshly collected intestinal fluid was investigated in the absence and presence of PCP–Cys. Permeation studies with PCP–Cys/GSH versus control were performed in vitro on Caco-2 cell monolayers and ex vivo on rat intestinal mucosa. PCP–Cys displayed 223 ± 13.8 μmol thiol groups per gram polymer. After 4 h, 61% of the free oligonucleotides were degraded by DNase I and 80% within intestinal fluid. In contrast, less than 41% (DNase I) and 60% (intestinal fluid) were degraded in the presence of 0.02% (m/v) PCP–Cys. Permeation studies revealed an 8-fold (Caco-2) and 10-fold (intestinal mucosa) increase in apparent permeability compared to buffer control. Hence, this PCP–Cys/GSH system might be a promising tool for the oral administration of oligonucleotides as it allows a significant protection toward degrading enzymes and facilitates their transport across intestinal membranes.
Keywords: Oligonucleotides; Polycarbophil; Thiomers; Permeation; Enzymes;

Thiomers: Inhibition of cytochrome P450 activity by Javed Iqbal; Duangkamon Sakloetsakun; Andreas Bernkop-Schnürch (361-365).
Comparison of IC50 values of test compounds for CYP3A4 and CYP2A6 inhibition.The aim of the present study was to investigate the potential of different thiolated polymers (thiomers) on the catalytic activity of CYP450s on one hand and to explore new inhibitors for CYP activity on the other hand. Several thiolated polymers including poly(acrylic acid)–cysteine (PAA–cysteine), chitosan–thioglycolic acid (chitosan–TGA), and thiolated PEG-g-PEI copolymer along with brij® 35, myrj® 52 and the well-established CYPP450 inhibitor verapamil were screened for their CYP3A4 and CYP2A6 inhibitory activity, and their IC50 values were determined. Both enzyme inhibition assays were performed in 96-well microtiter plates. 7-Benzyloxy-4-(trifluoromethyl)-coumarin (BFC) and 7-hydroxycoumarin (7-HC) were used as fluorescent substrates in order to determine CYP3A4 and CYP2A6 catalytic activity, respectively. All investigated compounds inhibited CYP3A4 as well as CYP2A6 activity. All tested (thiolated) polymers were found to be more potent inhibitors of CYP3A4 than of CYP2A6 catalytic activity. Apart from verapamil that is a known CYP3A4 inhibitor, brij® 35 and myrj® 52 were explored as potent inhibitors of CYP3A4 and CYP2A6 catalytic activity. Among the tested polymers, the rank order for CYP3A4 inhibition was PAA–cysteine (100 kDa) > brij® 35 > thiolated PEG-g-PEI copolymer (16 kDa) > myrj® 52 > PAA (100 kDa) > PAA–cysteine (450 kDa) > verapamil > PAA (450 kDa) > chitosan–TGA (150 kDa) > chitosan (150 kDa). On the other hand, the rank order of CYP2A6 inhibition was brij® 35 > PAA–cysteine (100 kDa) > chitosan–TGA (150 kDa) > PAA (100 kDa) > thiolated PEG-g-PEI copolymer (16 kDa) > PAA–cysteine (450 kDa) > chitosan (150 kDa) > verapamil > PAA (450 kDa) > myrj® 52. Thus, this study suggests that (thiolated) polymers display a promising potential to inhibit cytochrome P450s activity and might turn out to be potentially valuable tools for improving the oral bioavailability of actively secreted compounds by avoiding intestinal metabolism.
Keywords: Thiomers; Cytochrome P450; CYP3A4; CYP2A6; Inhibition; Fluorescent probe assays;

A new respirable form of rifampicin by Yoen-Ju Son; Jason T. McConville (366-376).
A novel respirable form of rifampicin (RF) has been manufactured by polymorphic transformation. SEM images of (A) rifampicin dihydrate (RFDH) and (B) spray-dried rifampicin (RFAM). The flaky RFDH showed significantly improved aerodynamic performances compared to the spherical RFAM since the unique morphology of RFDH crystals prevents the formation of strong particle aggregates.The aim of this research was to investigate a novel dry powder formulation of rifampicin (RF) that presents an improved lung deposition profile by means of a polymorphic transformation into a flake-like crystal hydrate. Rifampicin dihydrate (RFDH) was prepared by recrystallization of RF in anhydrous ethanol. A control formulation, amorphous RF (RFAM) was prepared by spray drying. The physicochemical properties of the RFDH and the RFAM were characterized. Aerosol performances of RFDH and RFAM were studied with two dry powder inhalers (DPIs), an Aerolizer® and a Handihaler®, using a Next Generation Impactor (NGI). The RFDH powder was successfully prepared using simple recrystallization process and had a MMAD of 2.2 μm. The RFDH powders were characterized as having a very thin flaky structure; this unique morphology provided improved aerosolization properties with a decreased device dependency upon aerosolization. The flaky morphology of RFDH resulted in a reduced agglomeration tendency than that of spherical RFAM particles. The maximum fine particle fraction (FPFTD) of 68% for the RFDH was achieved with the Aerolizer® device. Significant chemical degradation was not observed from the RFDH, while the RFAM showed significant chemical degradation at 9 months. The excipient-free formulation of the RFDH offers the benefit of delivering a maximum potency formulation, of the antibiotic, directly to the site of infection, the lung.
Keywords: Rifampicin; Polymorphism; Tuberculosis; Pulmonary; Crystal; Hydrate and dry powder inhaler;

Benznidazole microcrystal preparation by solvent change precipitation and in vivo evaluation in the treatment of Chagas disease by Flávia Pires Maximiano; Lívia Maria de Paula; Vivian Paulino Figueiredo; Isabel Mayer de Andrade; André Talvani; Lívia C. Sá-Barreto; Maria Terezinha Bahia; Marcílio S.S. Cunha-Filho (377-384).
The preparation of Benznidazole microcrystal, its incorporation into tablet matrix and the improvement in the drug therapeutic efficacy using murine model of Chagas disease.Benznidazole (BNZ) is traditionally used to treat Chagas disease. Despite its common use, BNZ has a poor water solubility and a variable bioavailability. The purpose of this study was to prepare BNZ microcrystals by solvent change precipitation and to study the effects of BNZ micronisation on therapeutic efficiency using a murine model of Chagas disease. The solvent change precipitation procedure was optimised in order to obtain stable and homogeneous particles with a small particle size, high yield and fast dissolution rate. The thermal and crystallographic analysis showed no polymorphic change in the microcrystals, and microscopy confirmed a significant reduction in particle size. A marked improvement in the drug dissolution rate was observed for micronised BNZ particles and BNZ tablets in comparison with untreated BNZ and commercial Rochagan®. In vivo studies showed a significant increase in the therapeutic efficacy of the BNZ microparticles, corroborating the dissolution results.
Keywords: Benznidazole; Chagas disease; Solvent change precipitation; Dissolution rate; Microcrystals;

Dissolution profiles (left) and apparent permeability values (right) of oxaprozin (OXA) alone or as physical mixture (PM) or co-ground product (GR) with RAMEB and chitosan (CS), with and without sodium ursodeoxycholate (NaUDC) or dehydrocholate (NaDHC).The effect of the combined use of randomly methylated β-cyclodextrin (RAMEB), chitosan (CS), and bile components (dehydrocholic (DHCA) or ursodeoxycholic (UDCA) acids and their sodium salts) on solubility and permeability through Caco-2 cells of oxaprozin (a very poorly water-soluble non-steroidal anti-inflammatory drug) has been investigated. Addition of CS, bile acids, and their sodium salts increased the RAMEB solubilizing power of 4, 2, and 5 times, respectively. Drug–RAMEB–CS co-ground systems showed very higher dissolution rate than corresponding drug–RAMEB systems. Addition of bile components further improved drug dissolution rate. The CS presence enabled a significant increase in drug permeability through Caco-2 cells with respect to drug–RAMEB systems. Moreover, CS and NaDHC showed a synergistic enhancer effect, enabling a 1.4-fold permeability increase in comparison with systems without bile salt. However, unexpectedly, no significant differences were found between physical mixtures and co-ground products, indicating that drug permeation improvement was due to the intrinsic enhancer effect of the carriers and not to drug-carrier interactions brought about by co-grinding, as instead found in dissolution rate studies. The combined use of RAMEB, CS, and NaDHC could be exploited to develop effective oral dosage forms of oxaprozin, with increased drug solubility and permeability, and then improved bioavailability.
Keywords: Oxaprozin; Solubility; Permeability through Caco-2 cells; Bile components; Cyclodextrin; Chitosan;

Drug release mechanisms of cast lipid implants by F. Kreye; F. Siepmann; J.F. Willart; M. Descamps; J. Siepmann (394-400).
The drug release mechanisms of cast lipid implants are complex and strongly depend on the systems’ composition. In case of pure diffusion control, drug release can be successfully predicted.The aim of this work was to better understand which physicochemical processes are involved in the control of drug release from lipid implants prepared by melting and casting. Lipid implants gain steadily in importance as controlled parenteral drug delivery systems: In contrast to PLGA-based devices, no acidic microclimates are created, which can inactivate incorporated drugs. The melting and casting method offers various advantages over the commonly used direct compression technique. For example, powder de-mixing during manufacturing and highly challenging scale-up due to poor powder flowability are avoided. Importantly, broad spectra of drug release patterns can be easily provided by varying the type of lipid. The resulting drug release rates are generally lower than those of implants prepared by direct compression. This is probably due to the differences in the microstructure of the pore network of the systems. Drug or water diffusion plays a dominant role for the control of drug release, potentially combined with limited drug solubility effects, caused by the low amounts of water available within the implants. In the case of pure diffusion control, a mechanistic realistic mathematical theory is proposed, which allows for quantitative predictions of the effects of formulation parameters on the resulting drug release kinetics. Importantly, these theoretical predictions could be successfully confirmed by independent experiments. Thus, the obtained new insight into the underlying drug release mechanisms can significantly facilitate the optimization of this type of advanced drug delivery systems. This is particularly helpful if long release periods are targeted, requiring time-consuming experimental studies.
Keywords: Lipid; Implant; Melting; Controlled release; Release mechanism;

Development and pharmacokinetic evaluation of erythromycin lipidic formulations for oral administration in rainbow trout (Oncorhynchus mykiss) by Francesca Serdoz; Dario Voinovich; Beatrice Perissutti; Iztok Grabnar; Dritan Hasa; Rodolfo Ballestrazzi; Ettore Coni; Enrico Pellegrini (401-407).
In this paper, to improve the oral bioavailability of erythromycin in rainbow trout, new formulations of medicated feed (based on two double microemulsions and a self-emulsifying system) were developed and tested in vivo, and their pharmacokinetic was studied.The aim of this work was to enhance the bioavailability of erythromycin base when administered orally in rainbow trout (Oncorhynchus mykiss). Since erythromycin is normally given in the form of medicated feed, in this study three new types of feed formulation were developed. A self-emulsifying system and two types of double microemulsions (O/W/O) were prepared, characterized and adsorbed on a commercial extruded diet for fish. The emulsified systems were based on saturated polyglycolized glycerides and mono- and diglycerides of medium-chain fatty acids (as oily phase), Tween® 80 (as surfactant) and, in the case of double microemulsions, distilled water. The systems differed in percentage composition and for the amount and position of erythromycin in different phases. The three medicated feed were then administered orally by means of a gastric probe to rainbow trout and their relative bioavailability was estimated in comparison with that obtained after oral administration of feed with erythromycin powder. For each medicated feed, 80 fish were tested. Finally, plasma profiles of erythromycin after single administration of medicated feeds were used to predict profiles obtainable by administering once-daily medicated feeds for 7 consecutive days. The results proved that the feeds containing microemulsified erythromycin provided largely superior oral bioavailability and the advantage of obtaining the same efficacy against bacterial infections with a much lower dose of drug.
Keywords: Aquaculture; Erythromycin; Self-emulsifying system; Double microemulsions; Medicated feed; Pharmacokinetics;

Laser microporation significantly increases diclofenac transport across the skin and enables a GI-sparing mode of administration.The objective of the study was to investigate the effect of laser microporation, using P.L.E.A.S.E.® technology, on diclofenac delivery kinetics. Skin transport of diclofenac was studied from aqueous solution, propylene glycol and marketed formulations across intact and laser-porated porcine and human skins; cumulative permeation and skin deposition were quantified by HPLC. After 24 h, cumulative diclofenac permeation across skins with 150, 300, 450 and 900 shallow pores (50–80 μm) was 3.7-, 7.5-, 9.2- and 13-fold superior to that across untreated skin. It was also found to be linearly dependent on laser fluence; Permeation (μg/cm2) = 11.35 * Fluence (J/cm2) + 352.3; r 2  = 0.99. After 24 h, permeation was 539.6 ± 78.1, 934.5 ± 451.5, 1451.9 ± 151.3 and 1858.6 ± 308.5 μg/cm2, at 22.65, 45.3, 90.6 and 135.9 J/cm2, respectively. However, there was no statistically significant effect of laser fluence on skin deposition. Diclofenac delivery from marketed gel formulations was also significantly higher across laser-porated skins (e.g. for Solaraze™, cumulative permeation after 24 h across treated (900 pores/135.9 J/cm2) and untreated skin was 974.9 ± 368.8 and 8.2 ± 3.8 μg/cm2, respectively. Diclofenac delivery from Solaraze™ across laser-porated porcine and human skins was also shown to be statistically equivalent. The results demonstrated that laser microporation significantly increased diclofenac transport from both simple and semi-solid formulations through porcine and human skin and that pore depth and pore number could modulate delivery kinetics. A similar improvement in topical diclofenac delivery in vivo may increase the number of potential therapeutic applications.
Keywords: Transdermal delivery; Stratum corneum ablation; P.L.E.A.S.E.®; Laser microporation; Diclofenac;

Microdialysis assessment of percutaneous penetration of ketoprofen after transdermal administration to hairless rats and domestic pigs by Norihiro Shinkai; Kazuko Korenaga; Yutaka Okumura; Hideo Mizu; Hitoshi Yamauchi (415-421).
Ketoprofen was readily found within patch-applied skin and knee joint after topical patch application, while it was hardly detectable in non-application sites.The study was performed to evaluate the percutaneous penetration of ketoprofen after transdermal administration using a microdialysis technique in pigs, in comparison with rats. Ketoprofen release from patches was determined by analysis of the remaining drug content after application to hairless rats and pigs. Skin and knee joint penetration of ketoprofen was tested by microdialysis, and recovery was determined by retrodialysis. Residual rates in hairless rats and pigs were 68.1 ± 1.6% and 81.7 ± 4.4%, respectively, at 10 h. The average recoveries of ketoprofen over 480 min in the skin and knee joint cases were 72.0 ± 3.4% and 9.8 ± 6.2% in rats and 72.3 ± 2.5% and 57.6 ± 3.1% in pigs, respectively. In rats, ketoprofen was rapidly absorbed with transdermal administration, with C max values of 191.7 ± 76.2 and 35.5 ± 21.7 ng/mL and AUC0–8h values of 918.2 ± 577.5 and 195.9 ± 137.1 ng h/mL, respectively, for the skin and knee joint. The C max values for the pig were 20.9 ± 18.5 and 3.7 ± 3.0 ng/mL, with AUC0–8h values of 73.1 ± 69.2 and 16.1 ± 16.1 ng h/mL. Ketoprofen concentrations within skin and knee joint of non-application sites in rats and pigs were less than 0.8 ng/mL. Transdermal administration of ketoprofen significantly reduced prostaglandin E2 levels in the skin of the application site and showed a tendency for inhibition in the knee joint. We thus demonstrated that topical patches containing ketoprofen can deliver the drug through the skin and knee joint of pigs and rats via direct diffusion, and microdialysis data with the pig may be useful for the prediction of human tissue penetration of drugs with transdermal administration.
Keywords: Ketoprofen; Topical patch; Transdermal penetration; Microdialysis; Pig and rat skin;

Enhancement of transdermal apomorphine delivery with a diester prodrug strategy by Kuo-Sheng Liu; K.C. Sung; Saleh A. Al-Suwayeh; Ming-Chuan Ku; Chin-Chen Chu; Jhi-Joung Wang; Jia-You Fang (422-431).
Diester prodrugs of apomorphine, diacetyl apomorphine (DAA), and diisobutyryl apomorphine (DIA) were synthesized, and their partition coefficients, capacity factor (log  K′), enzymatic hydrolysis, and in vitro permeation across nude mouse skin were characterized. Diesters showed that the main requirements needed for transdermal prodrugs are chemical stability, enzymatic lability, and an increase in the in vitro skin permeation.Diester prodrugs of apomorphine, diacetyl apomorphine (DAA), and diisobutyryl apomorphine (DIA) were synthesized, and their partition coefficients, capacity factor (log  K′), enzymatic hydrolysis, and in vitro permeation across nude mouse skin were characterized. The lipophilicity of the diesters was between that of apomorphine HCl and the apomorphine base. The prodrugs were chemically stable, but enzymatically unstable in esterase medium, skin homogenate, and human plasma. DAA showed a faster hydrolysis in plasma compared to DIA. Total fluxes (nmol/cm2/h) of the parent drug and prodrug were significantly greater after topical treatment with the diesters in aqueous solutions (water, 30% polyethylene glycol in water, and 30% glycerol in water) compared to treatment with HCl and base forms of apomorphine. DIA flux from deionized water was 51 nmol/cm2/h, which exceeded the flux of apomorphine HCl by 10-fold. The extent of parent drug regeneration after topical application ranged 51–88% and 34–61% for DAA and DIA, respectively, depending on the vehicles selected. Permeation measurements using intact and stratum corneum-stripped skins demonstrated that the viable epidermis/dermis was an important barrier to prodrug permeation. Nano-sized lipid emulsions were also used as carriers for apomorphine and its prodrugs. Diester prodrugs exhibited superior skin permeation compared to the parent drug when formulated into the emulsions. DAA and DIA fluxes from lipid emulsions were 11- and 3-fold higher than that of apomorphine HCl. The results in the present work suggest the feasibility of diester prodrugs for the transdermal delivery of apomorphine.
Keywords: Apomorphine; Prodrugs; Diesters; Transdermal delivery; Skin; Lipid emulsions;

Keratin film made of human hair as a nail plate model for studying drug permeation by Lusiana; Stephan Reichl; Christel C. Müller-Goymann (432-440).
Keratin film made of human hair as a nail plate model for studying drug permeation.The limited source of human nail plate for studying drug permeation inspired us to develop a nail plate model made of human hair keratin. The manufacturing process consisted of keratin extraction, dialysis, molding, solvent evaporation, and curing, producing a water-resistant film. The permeability of the film was examined using three markers: sodium fluorescein, rhodamine B, and fluorescein isothiocyanate–dextran as water-soluble, lipid-soluble, and large molecule models, respectively. Bovine hoof was used for comparison. First investigation showed that keratin films (thickness 120 μm) resembled hooves (thickness 100 μm) except that these films were more permeable to rhodamine B compared with hooves (1.8-fold, p  < 0.01). Subsequent investigations using ungual penetration enhancers (urea, thioglycolic acid, and papain) showed that keratin films were generally more susceptible than hooves. This study revealed that the produced keratin film offers a possibility as a human nail plate substitute. However, inclusion of the penetration enhancer must be carefully interpreted.
Keywords: Keratin; Bovine hoof; Hair; Nail; Permeation study; Marker;

Investigation of preparation parameters of nanosuspension by top-down media milling to improve the dissolution of poorly water-soluble glyburide by Sachin Kumar Singh; K.K. Srinivasan; K. Gowthamarajan; Dhananjay S. Singare; Dev Prakash; Narayan Babulal Gaikwad (441-446).
Glyburide nanosuspension was prepared by dispersing the drug and the stabilizers in the milling media and then subjected to milling chamber of bead mill for particle size reduction at a feed rate of 100ml/min at 2800 rpm for 6.5 h at 18–20°C . The formed nanosuspension has shown an enhancement in the dissolution rate when compared with the unmilled drug.The objective of this study was to identify and optimize formulation and process variables affecting characteristic and scale-up of nanosuspension manufacturing process on bead mill considering industrial perspective. Formulation factors evaluated were ratio of polymer to drug and ratio of surfactant to drug, whereas process parameters were milling time and milling speed. Responses measured in this study include zeta potential and mean particle size d(90). The test revealed that ratio of polymer to drug and milling speed have significant effect on zeta potential whereas milling time and milling speed have significant effect on the particle size distribution of nanosuspension. The X-ray powder diffraction pattern of drug milled at high and low speed reveals no form conversion when compared with unmilled drug. The formulated nanosuspension has shown a faster dissolution profile (98.97% in 10 min), relative to that of raw glyburide (18.17% in 10 min), mainly due to the formation of nanosized particles. The ANOVA test revealed that there was no significant difference in the dissolution profiles of fresh and aged nanosuspension. These results indicate the suitability of formulation procedure for preparation of nanosized poorly water-soluble drug with significantly improved in vitro dissolution rate and thus possibly enhance fast onset of therapeutic drug effect.
Keywords: Bead mill; Zeta potential; Nanosuspension; Mean particle size d(90); X-ray powder diffraction; Unmilled drug;

Enteric polymers as acidifiers for the pH-independent sustained delivery of a weakly basic drug salt from coated pellets by Martin Körber; Mesut Ciper; Valerie Hoffart; Nantharat Pearnchob; Mathias Walther; Ross J. Macrae; Roland Bodmeier (447-454).
Incorporation of enteric polymers into ethylcellulose-coated modified release pellets facilitated flexible and approximately pH-independent release of a drug with an exceptional pH-dependent solubility, oppositely to incorporation of low molecular weight acid or coatings with enteric/non-enteric polymers.Weakly basic drugs and their salts exhibit a decrease in aqueous solubility at higher pH, which can result in pH-dependent or even incomplete release of these drugs from extended release formulations. The objective of this study was to evaluate strategies to set-off the very strong pH-dependent solubility (solubility: 80 mg/ml at pH 2 and 0.02 mg/ml at pH 7.5, factor 4000) of a mesylate salt of weakly basic model drug (pK a 6.5), in order to obtain pH-independent extended drug release. Three approaches for pH-independent release were investigated: (1) organic acid addition in the core, (2) enteric polymer addition to the extended release coating and (3) an enteric polymer subcoating below the extended release coating. The layering of aspartic acid onto drug cores as well as the coating of drug cores with an ethylcellulose/Eudragit L (enteric polymer) blend were not effective to avoid the formation of the free base at pH 7.5 and thus failed to significantly improve the completeness of the release compared to standard ethylcellulose/hydroxypropyl cellulose (EC/HPC)-coated drug pellets. Interestingly, the incorporation of an enteric polymer layer underneath the EC/HPC coating decreased the free base formation at pH 7.5 and thus resulted in a more complete release of up to 90% of the drug loading over 18 h. The release enhancing effect was attributed to an extended acidification through the enteric polymer layer. Flexible release patterns with approximately pH-independent characteristics were successfully achieved.
Keywords: Weakly basic drug; Controlled drug release; Coating; Pellets; Non-enteric; Enteric; Polymer blend; Ethylcellulose; Eudragit L; Microenvironmental pH; Multiparticulates;

Dynamic and static curing of ethylcellulose:PVA–PEG graft copolymer film coatings by S. Muschert; F. Siepmann; B. Leclercq; J. Siepmann (455-461).
Long term stable, coated pellets with predominantly diffusion controlled drug release can be prepared via dynamic or static curing.When using aqueous polymer dispersions for the preparation of controlled-release film coatings, instability during long-term storage can be a crucial concern. Generally, a thermal after treatment is required to assure sufficient polymer particle coalescence. This curing step is often performed under static conditions in an oven, which is a time-consuming and rather cumbersome process. Dynamic curing in the fluidized bed presents an attractive alternative. However, yet little is known on the required conditions, in particular: temperature, time, and relative humidity, to provide stable film structures. The aim of this study was to better understand the importance of these key factors and to evaluate the potential of dynamic curing compared with that of static curing. Recently proposed ethylcellulose:poly(vinyl alcohol)–poly(ethylene glycol) graft copolymer (PVA–PEG graft copolymer) dispersions were coated on theophylline and metoprolol succinate-loaded starter cores, exhibiting different osmotic activity. Importantly, processing times as short as 2 h were found to be sufficient to provide long-term stable films, even upon open storage under stress conditions. For instance, 2-h dynamic curing at 57 °C and 15% relative humidity are assuring stable film structures in the case of theophylline matrix cores coated with 15% ethylcellulose:PVA–PEG graft copolymer 85:15. Importantly, the approach is also applicable to other types of drugs and starter cores, and the underlying drug release mechanisms remain unaltered.
Keywords: Controlled release; Film coating; Curing; Aqueous dispersion; Mathematical modeling; Ethylcellulose;

ODMTs, as a novel oral dosage form for young children, are a very promising approach for replacement of liquids.The new European regulations on paediatric medicines and recent WHO recommendations have induced an increased need for research into novel child-appropriate dosage forms. The aim of this study was the development of orally disintegrating mini-tablets (ODMTs) as a suitable dosage form for paediatric patients. The suitability of five commercially available ready-to-use tableting excipients, Ludiflash®, Parteck® ODT, Pearlitol® Flash, Pharmaburst® 500 and Prosolv® ODT, to be directly compressed into mini-tablets, with 2 mm in diameter, was examined. All of the excipients are based on co-processed mannitol. Drug-free ODMTs and ODMTs with a child-appropriate dose of hydrochlorothiazide were investigated.ODMTs could be produced with all investigated excipients. ODMTs with a sufficient crushing strength >7 N and a low friability <1% could be obtained, as well as ODMTs with a short simulated wetting test-time <5 s. ODMTs made of Ludiflash® showed the best results with crushing strengths from 7.8 N up to 11.8 N and excellent simulated wetting test-times from 3.1 s to 5.0 s. For each excipient, ODMTs with accordance to the pharmacopoeial specification content uniformity could be obtained. The promising results indicate that orally disintegrating mini-tablets may serve as a novel platform technology for paediatrics in future.
Keywords: Mini-tablet; Co-processed; Paediatrics; Orally disintegrating; Hydrochlorothiazide; Children;

Release of theophylline and carbamazepine from matrix tablets – Consequences of HPMC chemical heterogeneity by Anna Viridén; Susanna Abrahmsén-Alami; Bengt Wittgren; Anette Larsson (470-479).
Drug release from hydrophilic matrices composed of two HPMC batches of the same substituent and viscosity grade but with different substituent heterogeneity. The release of the poorly soluble carbamazepine was considerably slower from matrices composed of the HPMC with heterogeneous substituent pattern. This was explained by slower polymer erosion of the heterogeneous HPMC and the fact that carbamazepine was mainly released by erosion. The release of the sparingly soluble theophylline was more comparable from the two formulations, which was explained by the similar water transports into the tablets and the similar diffusion paths of theophylline..The release of theophylline and carbamazepine from matrix tablets composed of microcrystalline cellulose, lactose and hydroxypropyl methylcellulose (HPMC) was studied. The aim was to investigate the effect of different substituent heterogeneities of HPMC on the drug release from matrix tablets composed of either 35% or 45% HPMC. The release of the poorly soluble carbamazepine was considerably affected by the HPMC heterogeneity, and the time difference at 80% drug release was more than 12 h between the formulations of different HPMC batches. This was explained by slower polymer erosion of the heterogeneous HPMC and the fact that carbamazepine was mainly released by erosion. In addition, results from magnetic resonance imaging showed that the rate of water transport into the tablets was similar. This explained the comparable results of the release of the sparingly soluble theophylline from the two formulations even though the polymer erosion and the swelling of the tablets were considerably different. Thus, it can be concluded that the drug release was highly affected by the substituent heterogeneity, especially in the case of carbamazepine, which was released mainly by erosion.
Keywords: Hydrophilic matrix tablets; Drug release; Drug solubility; Batch-to-batch variability; HPMC chemical heterogeneity; MRI;

A comparative study of the physicochemical properties of iron isomaltoside 1000 (Monofer®), a new intravenous iron preparation and its clinical implications by Markus R. Jahn; Hans B. Andreasen; Sören Fütterer; Thomas Nawroth; Volker Schünemann; Ute Kolb; Wolfgang Hofmeister; Manuel Muñoz; Klaus Bock; Morten Meldal; Peter Langguth (480-491).
Transmission electron microscopic image of iron isomaltoside 1000.The treatment of iron deficiency anemia with polynuclear iron formulations is an established therapy in patients with chronic kidney disease but also in other disease areas like gastroenterology, cardiology, oncology, pre/post operatively and obstetrics’ and gynecology. Parenteral iron formulations represent colloidal systems in the lower nanometer size range which have traditionally been shown to consist of an iron core surrounded by a carbohydrate shell. In this publication, we for the first time describe the novel matrix structure of iron isomaltoside 1000 which differs from the traditional picture of an iron core surrounded by a carbohydrate. Despite some structural similarities between the different iron formulations, the products differ significantly in their physicochemical properties such as particle size, zeta potential, free and labile iron content, and release of iron in serum. This study compares the physiochemical properties of iron isomaltoside 1000 (Monofer®) with the currently available intravenous iron preparations and relates them to their biopharmaceutical properties and their approved clinical applications. The investigated products encompass low molecular weight iron dextran (CosmoFer®), sodium ferric gluconate (Ferrlecit®), iron sucrose (Venofer®), iron carboxymaltose (Ferinject®/Injectafer®), and ferumoxytol (Feraheme®) which are compared to iron isomaltoside 1000 (Monofer®). It is shown that significant and clinically relevant differences exist between sodium ferric gluconate and iron sucrose as labile iron formulations and iron dextran, iron carboxymaltose, ferumoxytol, and iron isomaltoside 1000 as stable polynuclear formulations. The differences exist in terms of their immunogenic potential, safety, and convenience of use, the latter being expressed by the opportunity for high single-dose administration and short infusion times. Monofer is a new parenteral iron product with a very low immunogenic potential and a very low content of labile and free iron. This enables Monofer, as the only IV iron formulation, to be administered as a rapid high dose infusion in doses exceeding 1000 mg without the application of a test dose. This offers considerable dose flexibility, including the possibility of providing full iron repletion in a single infusion (one-dose iron repletion).
Keywords: Inorganic nanoparticles; Colloids; Stability; Free iron; Iron supplementation; Release rate;

A comparative study of glycerin fatty acid ester and magnesium stearate on the dissolution of acetaminophen tablets using the analysis of available surface area by Takeaki Uchimoto; Yasunori Iwao; Kana Takahashi; Shoko Tanaka; Yasuyoshi Agata; Takeru Iwamura; Atsuo Miyagishima; Shigeru Itai (492-498).
Schematic illustration of the relationship between the mechanism of tablet disintegration and the available surface area.To study the effect of glycerin fatty acid ester (Poem TR-FB) concentrations on the dissolution rate of acetaminophen (APAP), the dissolution and disintegration behaviors of APAP tablets formulated using various lubricants were examined. The change over time in the available surface area of APAP (S(t)), which is in direct contact with solvent, was also analyzed using these dissolution data. In the dissolution tests, a retarded dissolution of APAP was not observed with TR-FB, whereas magnesium stearate (Mg-St), which is widely used as a lubricant, retarded the dissolution. However, no significant difference in the disintegration time between the two lubricants was observed. With regard to the time course of the S(t), Mg-St at 0.1% gave a maximum surface area value at 9.19 min (peak time); however, the profiles for APAP with Mg-St at greater than 0.5% showed downward curvature indicating a gradual decrease in surface area over time. Conversely, with TR-FB, even when its concentration was increased, the S(t) profile for APAP had a maximum value that was more than twice that of APAP with that of 0.5–3.0% of Mg-St. Scanning electron microscopy (SEM) observations showed that the differences in the dissolution rate and S(t) patterns between Mg-St and TR-FB could be explained by differences in extensibility deriving from their morphology. Therefore, it was concluded that TR-FB does not cause retardation of drug dissolution and may prove to be a superior alternative lubricant to Mg-St.
Keywords: Glycerin fatty acid esters; Magnesium stearate; Dissolution rate; Available surface area; Extensibility;

Formulation of zolmitriptan sublingual tablets prepared by direct compression with different polymers: In vitro and in vivo evaluation by Ziya Bayrak; Cetin Tas; Umut Tasdemir; Halil Erol; Cansel Kose Ozkan; Ayhan Savaser; Yalcin Ozkan (499-505).
Sublingual administration of zolmitriptan formulated with appropriate excipients and polymers seems promising alternative to traditional routes.First-pass metabolism can be overcome by sublingual drug delivery, and quick drug entry into the systemic circulation can be obtained. In certain diseases such as migraine therapy, taking fast pharmacological response is an important criteria. In this study, zolmitriptan sublingual tablets were prepared by direct compression method using different mucoadhesive polymers such as hydroxypropyl methyl cellulose, chitosan and sodium carboxy methyl cellulose at a concentration range of 0.5–5% to reduce flushing action of saliva and provide enough time for drug to be absorbed. Tablets were evaluated for the physical properties, and optimum formulations were chosen for in vivo studies to carry on sheep model. The tablets disintegrated rapidly, and dissolution tests revealed that zolmitriptan was dissolved from the formulation within the compendial limits. This especially showed us that the concentration range of polymers is in acceptable limit. It was also concluded that microcrystalline cellulose, spray-dried lactose and sodium starch glycolate are the appropriate excipient and formulated in good proportions. In vivo studies indicated that formulation containing 5% chitosan has the maximum C max and AUC and minimum t max values (p  < 0.05). As a result, sublingual tablet administration of zolmitriptan formulated with appropriate excipients and especially with chitosan seems promising alternative to traditional routes.
Keywords: Sublingual delivery; Zolmitriptan; Chitosan; Hydroxylpropylmethyl cellulose; Sodium carboxy methyl cellulose; Permeability;

Rheological study of the mixture of acetaminophen and polyethylene oxide for hot-melt extrusion application by Herman Suwardie; Peng Wang; David B. Todd; Viral Panchal; Min Yang; Costas G. Gogos (506-512).
Reduced viscosity of APAP-PEO mixture at different temperature. The drug’s solubility in the molten polymer is given by the lowest point of each curve.There is a growing interest of extrusion drug and polymer together to manufacture various solid dosages. In those cases, the drug’s release profiles are greatly affected by the miscibility of two materials. The goal of this study is to test the drug’s solubility in molten polymer and obtain the mixture’s rheological properties for the purpose of optimizing the extrusion process. The dynamic and steady viscosities of APAP–PEO mixture were determined using oscillatory and capillary rheometers. The curves of viscosity vs. drug loading generally have a “V” shape, and the minimal point gives the APAP’s solubility in PEO. The test results suggest that different dynamic methods lead to essentially the same solubility data. At high shear rates, the mixtures show shear thinning behavior and the viscosity becomes less sensitive to the drug loading. In other words, it is desirable to use a low shear rate in order to deduce the drug’s solubility in polymer from the viscosity data. On the other hand, viscosity data at high shear rates are more representative of the materials’ rheological properties during extrusion.
Keywords: Hot-melt extrusion; Rheology; Viscosity; Viscoelasticity; Solubility; Rheometer;

Combining microwave resonance technology to multivariate data analysis as a novel PAT tool to improve process understanding in fluid bed granulation by Vera Lourenço; Thorsten Herdling; Gabriele Reich; José C. Menezes; Dirk Lochmann (513-521).
The in-line monitoring of granulation batches using a Microwave Resonance Technology (MRT) sensor combined to multivariate data analysis techniques led to improved process knowledge. Differences on the final granule size histograms could be found depending on the path taken by the process.A set of 192 fluid bed granulation batches at industrial scale were in-line monitored using microwave resonance technology (MRT) to determine moisture, temperature and density of the granules. Multivariate data analysis techniques such as multiway partial least squares (PLS), multiway principal component analysis (PCA) and multivariate batch control charts were applied onto collected batch data sets. The combination of all these techniques, along with off-line particle size measurements, led to significantly increased process understanding. A seasonality effect could be put into evidence that impacted further processing through its influence on the final granule size. Moreover, it was demonstrated by means of a PLS that a relation between the particle size and the MRT measurements can be quantitatively defined, highlighting a potential ability of the MRT sensor to predict information about the final granule size.This study has contributed to improve a fluid bed granulation process, and the process knowledge obtained shows that the product quality can be built in process design, following Quality by Design (QbD) and Process Analytical Technology (PAT) principles.
Keywords: Fluid bed granulation; PAT; Microwave resonance technology; Multivariate data analysis; Batch monitoring; QbD;

Volume to dissolve applied dose (VDAD) and apparent dissolution rate (ADR): Tools to predict in vivo bioavailability from orally applied drug suspensions by Uwe Muenster; Christian Pelzetter; Thomas Backensfeld; Andreas Ohm; Thomas Kuhlmann; Hartwig Mueller; Klemens Lustig; Jörg Keldenich; Susanne Greschat; Andreas H. Göller; Mark Jean Gnoth (522-530).
In vitroin vivo correlation of dissolution and solubility data allows the deduction of critical dose/solubility ratios, which are predictive of whether or not a dissolution-related impairment of bioavailability can be expected after application of oral dosage forms containing crystalline API.Low solubility of drug candidates generated in research contributes to their elimination during subsequent development due to insufficient oral bioavailability (BA) of crystalline compound. Therefore, the purpose of the study was to identify critical in vitro solubility and dissolution parameter that would predict critical in vivo dissolution by means of in vitro–in vivo correlation. Thermodynamic solubility and apparent dissolution rate (ADR) were determined using the shake-flask method and mini-flow-through-cell, respectively. Oral BA studies in rats and humans were conducted from drug solution and suspension/tablets. Relative BA was calculated using F rel [%] = AUCsuspension/AUCsolution  * 100, representing a measure of in vivo dissolution. Roughly, F rel rat >50% translates into F rel human of >90%. Both, ADR and log volume to dissolve applied dose (VDAD), when plotted against F rel rat, revealed certain threshold levels, (ADR, ∼150–200 μg of compound dissolved under respective assay conditions; VDAD, ∼100–500 ml/kg) which translate into F rel in rats of >50%.Thus, assuming that F rel  > 50% in rats is indicative of sufficient in vivo dissolution in humans after oral application, drugs should exhibit a VDAD of ∼100–500 ml/kg or less in aqueous media to avoid insufficient or varying drug absorption.
Keywords: Solubility; Dissolution; Bioavailability; Absorption; Development;

Use of conventional surfactant media as surrogates for FaSSIF in simulating in vivo dissolution of BCS class II drugs by Paula Lehto; Hanna Kortejärvi; Anni Liimatainen; Krista Ojala; Heli Kangas; Jouni Hirvonen; Veli Pekka Tanninen; Leena Peltonen (531-538).
With the aid of successful in vitro dissolution testing and simulation prediction of drug absorption in vivo is possible.The usefulness of selected conventional surfactant media to enhance dissolution of BCS class II drugs similarly to fasted state simulated intestinal fluid (FaSSIF) and to predict the absorption of drugs in vivo was evaluated. Dissolution behavior of danazol (Danol®), spironolactone (Spiridon®) and N74 (phase I compound) was compared between FaSSIF, containing physiological levels of sodium taurocholate (STC) and lecithin, and dissolution media containing various concentrations of anionic surfactant, sodium lauryl sulfate (SLS) or non-ionic surfactant, polysorbate (Tween) 80. Although these media differed largely in their solubilization ability, micelle size, diffusivity and surface tension, similar dissolution enhancing levels were achieved between FaSSIF and drug-specific concentrations of conventional surfactants. The dissolution enhancement was shown, however, to be important only for danazol and N74, molecules that are characterized by high hydrophobicity. An in vivo pharmacokinetic dog study was carried out with N74. Comparison of observed plasma profiles with simulated profiles obtained using compartmental absorption and transit model (CAT) indicated that 0.1% SLS medium was the best to predict in vivo plasma profiles and pharmacokinetic parameters (Cmax and AUC). This study demonstrates the potential of substituting FaSSIF with more simple and cost-effective conventional surfactant media. Use of in vivo prognostic amounts of synthetic surfactants in dissolution testing could largely assist in industrial drug development as well as in quality control purposes.
Keywords: Biorelevant media; Compartmental absorption and transit (CAT) model; Fasted state simulated intestinal fluid (FaSSIF); Dissolution; In vitroin vivo correlation (IVIVC); Pharmacokinetic simulation;