Light sensitive blood thinners

A new drug that is its own antidote could save patients who require anticlotting drugs from dying of internal bleeding if they inadvertently overdose on the drug. Unfractionated heparin is currently the only blood-clotting inhibitor for which a specific antidote exists. Now, Alexander Heckel, Günter Mayer, and Bernd Pötzsch in Bonn, Germany, have developed a new class of anticoagulant based on aptamers, simple strands of DNA. The new drug blocks blood clotting until it is exposed to ultraviolet light at which point an auxiliary DNA strand isomerises, distorts the drug's structure and prevents it from binding to thrombin. Its anticoagulant activity is switched off immediately.