What are the side effects of Minoxidil (minoxidil) tablets?

Side Effects of Minoxidil Tablets

Minoxidil tablets can cause several significant side effects including hirsutism, fluid retention requiring loop diuretics, reflex tachycardia requiring beta-blockers, and potentially life-threatening pericardial effusion. 1

Major Side Effects

Cardiovascular Effects

• Fluid retention and sodium retention: Occurs in most patients and can be severe, requiring concomitant use of loop diuretics 1
• Reflex tachycardia: Due to vasodilation, requires concomitant beta-blocker therapy 1
• Pericardial effusion: A rare but serious idiosyncratic reaction that can be life-threatening 1, 2
• Potential aggravation of myocardial ischemia: Due to tachycardia 3
• Left ventricular hypertrophy: With long-standing tachycardia 3

Dermatologic Effects

• Hirsutism (excessive hair growth): Universal side effect that occurs in virtually all patients, particularly problematic for women 1

Management Considerations

Minoxidil is classified as a "direct vasodilator" and is generally reserved as a last-line therapy for resistant hypertension due to its side effect profile 1. When prescribing minoxidil:

1. Always combine with:

   • A loop diuretic (to manage fluid retention)
   • A beta-blocker (to control reflex tachycardia)

2. Dosing:

   • Initial dose: 5 mg daily
   • Dose range: 5-100 mg daily
   • Frequency: 1-3 times daily 1

3. Monitoring requirements:

   • Regular assessment for fluid retention (weight gain, edema)
   • Heart rate monitoring
   • Echocardiography if symptoms suggest pericardial effusion
   • Renal function (particularly important in patients with kidney disease)

Special Populations

• Patients with renal impairment: Higher risk of significant fluid retention; may require higher doses of diuretics 2
• Women: The universal hirsutism significantly limits acceptability and use 2
• Patients with heart disease: Reflex tachycardia may worsen ischemia; careful beta blockade is essential 3

Clinical Pearls

• Minoxidil should only be used when hypertension is resistant to multiple other medications 1
• Despite its side effects, minoxidil can be effective in controlling blood pressure in patients with truly resistant hypertension 2, 4
• Some patients report improved sense of wellbeing on minoxidil compared to other antihypertensive regimens 2
• Consider referral to a hypertension specialist when minoxidil therapy is being considered 3
• Discontinuation of minoxidil may be necessary if pericardial effusion develops 5

Minoxidil's potent antihypertensive effects must be carefully weighed against its significant side effect profile, and it should be reserved for cases where other antihypertensive combinations have failed.