This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anti Microbial, Subject name: Pharmacology
[{'content': 'Use of tadalafil is contraindicated in: \nSelect and explain. \nA. Pulmonary arterial hypertension, B. Unstable/Symptomatic angina, C. Active infections, D. Hepatic dysfunction', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. b. Unstable/Symptomatic anginaRef: Goodman Gilman 12th e/P. 841Nitrates increase cyclic GMP production by stimulation of guanylate cyclase via NO. This cyclic GMP is responsible for vasodilation.Cyclic GMP is metabolized by PDE-5 and hence PDE-5 inhibitors like sildenafil and tadalafil can significantly increase cyclic GMP producing fatal hypotension.Thus tadalafil is contraindicated with nitrates and hence unstable/symptomatic angina is the best answer.', 'role': 'assistant'}]