A 62-year-old man takes sildenafil regularly and now attends a clinic for newly prescribed antianginal therapy. Which combination must be strictly avoided, and what is the mechanism of the resulting event?
- A Sildenafil with atenolol: additive bradycardia and heart block
- B Sildenafil with amlodipine: severe reflex tachycardia
- C Sildenafil with nitroglycerin: catastrophic fall in blood pressure ✓
- D Sildenafil with aspirin: spontaneous coronary dissection
Correct answer: C. Sildenafil with nitroglycerin: catastrophic fall in blood pressure
Explanation
Nitrates increase cyclic GMP in vascular smooth muscle by releasing nitric oxide that stimulates guanylyl cyclase. Sildenafil blocks the degradation of cyclic GMP by phosphodiesterase type 5. Together they cause massive, unopposed vasodilation with profound hypotension, syncope and death. The combination is absolutely contraindicated within 24 hours of sildenafil and longer for tadalafil. Atenolol causes only mild additive lowering of blood pressure and no such catastrophe.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
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Written and medically reviewed by the StethoPrep medical team.