Verapamil is a potent inhibitor of 5-HT-induced platelet aggregation.
We have studied the effects of verapamil, diltiazem and amlodipine on 5-HT-induced platelet aggregation and compared the results with those obtained for other platelet aggregating agents. Experiments were carried out using both human whole blood and platelet-rich plasma (PRP). Verapamil (but not diltiazem or amlodipine) inhibited 5-HT-induced platelet aggregation at much lower concentrations (IC50 = about 1 microM) than were required for inhibition of aggregation induced by other aggregating agents. Like some other selective inhibitors of 5-HT-induced platelet aggregation, it was not possible to completely overcome the inhibition by increasing the concentration of 5-HT. The antiaggregatory effects of verapamil were similar, but not identical, in whole blood and PRP. These results show that the Ca2+ channel blocker verapamil has some selectivity as an inhibitor of 5-HT-induced platelet aggregation and that this behaviour as a 5-HT antagonist should be taken into account when interpreting any therapeutic benefit ascribed to this drug.
Glusa
E
E
Department of Pharmacology, Medical Academy, Erfurt, G.D.R.
Bevan
J
J
Heptinstall
S
S
D000244:Adenosine Diphosphate / Q000037:antagonists & inhibitors; D017311:Amlodipine; D002121:Calcium Channel Blockers / Q000494:pharmacology; D003094:Collagen / Q000037:antagonists & inhibitors; D004110:Diltiazem / Q000494:pharmacology; D004837:Epinephrine / Q000037:antagonists & inhibitors; D006801:Humans; D066298:In Vitro Techniques; D009543:Nifedipine / Q000031:analogs & derivatives / Q000494:pharmacology; D010972:Platelet Activating Factor / Q000037:antagonists & inhibitors; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors; D012702:Serotonin Antagonists; D014700:Verapamil / Q000494:pharmacology*
D002121:Calcium Channel Blockers; D010972:Platelet Activating Factor; D010975:Platelet Aggregation Inhibitors; D012702:Serotonin Antagonists; D017311:Amlodipine; D000244:Adenosine Diphosphate; D003094:Collagen; D014700:Verapamil; D004110:Diltiazem; D009543:Nifedipine; D004837:Epinephrine