A young woman with severe resistant hypertension is started on oral minoxidil. Within two months her blood pressure is controlled but she requests advice about new facial and forearm hair growth. The correct counselling is:

• A Hypertrichosis signals androgen excess and warrants testosterone measurement
• B Hypertrichosis is dose related and reversible on stopping the drug; reflex tachycardia should be covered with a beta-blocker ✓
• C Hair growth indicates drug failure and the dose should be doubled
• D Minoxidil must be stopped immediately because hypertrichosis heralds malignant hypertension

Explanation

Minoxidil is a potent arteriolar vasodilator acting by opening ATP-sensitive potassium channels in vascular smooth muscle. Reflex sympathetic activation causes tachycardia, fluid retention and renin release, so it is combined with a beta-blocker and a diuretic. Hypertrichosis occurs in most patients, more in women, is dose related and reversible on discontinuation. It reflects a local growth effect on hair follicles, not androgen excess or treatment failure.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

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Written and medically reviewed by the StethoPrep medical team.