Amitriptyline can potentiate the hypotensive effect of GTN. Which option lists this as the correct drug?

• A. Metformin
• B. Lisinopril
• C. Atorvastatin
• D. Amitriptyline

Answer: (D)

GTN lowers blood pressure mainly by dilating veins, which reduces preload and systemic vascular resistance. Some drugs can magnify this effect. Amitriptyline, a tricyclic antidepressant, has alpha-1 adrenergic blocking properties that promote vascular smooth muscle relaxation and can cause orthostatic hypotension. When combined with GTN, these effects add up, increasing the risk and degree of hypotension more than either drug alone. The other drugs listed—metformin, lisinopril, and atorvastatin—do not have this specific interaction with nitrates; metformin acts on glucose metabolism, lisinopril lowers BP via ACE inhibition without the same vasodilatory synergy with GTN, and atorvastatin doesn’t affect vascular tone in this way.