Minoxidil is a type of drug that induces vasodilation. It does this by opening potassium channels to induce smooth muscle relaxation, which ultimately leads to arterial dilation. Clinically, minoxidil is used topically to treat male pattern hair growth. In rare cases, this drug can be administered systemically to treat severe refractory hypertension unresponsive to other drugs. Adverse effects of minoxidil include hypertrichosis or excess hair growth, as well as reflex tachycardia.

Key Points

  • Minoxidil
    • Mechanism
      • Direct Arterial Vasodilator
        • Opens K+ channels → hyperpolarizes vascular smooth muscle → smooth muscle relaxation
    • Clinical Use
      • Male Pattern Hair Loss
        • Mechanism is unclear: vasodilation is thought to increase blood flow and nutrient delivery to hair follicles
        • Topical formulation is used
      • Severe Refractory Hypertension
        • Used very rarely - only in patients who do not respond adequately to maximum therapeutic doses of a diuretic and 2 other antihypertensive agents
    • Adverse Effects
      • Hypertrichosis
        • Excessive hair growth
      • Reflex tachycardia