This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Hematology, Subject name: Pharmacology
[{'content': 'Asprin is not given in a patient who is already on heparin because aspirin causes: \nSelect and explain. \nA. Platelet dysfunction, B. Aspirin inhibits the action of heparin, C. Enhanced hypersensitivity of heparin, D. Therapy of heparin cannot be monitored', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Aspirin inactivates cyclo-oxygenase by irreversible acetylation of the enzyme and thereby inhibit the synthesis of thromboxane A2. Thromboxane A2 normally promotes platelet aggregation. This COX inhibition lasts for 7 - 10 days till fresh platelets are formed. From medical pharmacology padmaja 4th edition Page no 344', 'role': 'assistant'}]