Prevention of the platelet alpha-granule release reaction by membrane-active drugs

A range of membrane-active drugs were tested for their ability to prevent beta-thromboglobulin and platelet factor 4 release from freshly collected blood platelets. While all the drugs tested could inhibit collagen-induced platelet aggregation, only a few, notably procaine and the anti-malarial drugs chloroquine, hydroxychloroquine, camoquine and quinacrine (mepacrine), effectively prevented the alpha-granule release reaction.