This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Histamine, 5-HT and PGs, Subject name: Pharmacology
All of the following effects are produced by inhibitors of prostaglandin synthesis EXCEPT: 
Select and explain. 
A. Prolongation of bleeding time, B. Prolongation of prothrombin time, C. Prolongation of labour, D. Gastric mucosal damage
B: Prolongation of prothrombin time
Answer: B: Prolongation of prothrombin time 
Explanation: Prothrombin time is increased by the drugs interfering with the coagulation pathway (e.g. warfarin). As COX has no role in coagulation, inhibitors of PG synthesis do not prolong PT. However, bleeding time (BT) is prolonged by the drugs interfering with platelet function. Aspirin increases BT by acting as an antiplatelet agent.