Minoxidil Side Effects

Some side effects of minoxidil may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

For the Consumer

Applies to minoxidil: oral tablet

Get emergency medical help if you have any of these signs of an allergic reaction while taking minoxidil: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have a serious side effect such as:

• dry cough, sharp or stabbing chest pain;

• chest pain spreading to the arm or shoulder, nausea, sweating, general ill feeling;

• trouble breathing (especially while lying down);

• swelling in your legs, ankles, or feet;

• rapid weight gain of 5 pounds or more;

• fast or pounding heartbeats;

• sudden numbness, weakness, headache, confusion, or problems with vision, speech, or balance;

• fever, sore throat, and headache with a severe blistering, peeling, and red skin rash;

• the first sign of any skin rash, no matter how mild;

• easy bruising or bleeding; or

• feeling like you might pass out.

Less serious side effects of minoxidil may include:

• nausea, vomiting;

• breast pain or tenderness; or

• changes in the color, length, or thickness of body or facial hair.

This is not a complete list of side effects and others may occur. Tell your doctor about any unusual or bothersome side effect.

For Healthcare Professionals

Applies to minoxidil: compounding powder, oral tablet

General

Minoxidil is usually administered with a beta-blocker to counteract the increased cardiac output and cardiac work associated with profound minoxidil-induced vasodilation and with a loop diuretic to counteract the sodium and water retaining properties of minoxidil.

Cardiovascular

Cardiovascular side effects are related to peripheral vasodilation and sodium and water retention, and include hypotension, sinus tachycardia, provocation of angina, edema, and weight gain. Edema is expected without concomitant use of a diuretic agent.

Pericardial effusions occur in up to 5% of patients and may be more likely in patients with renal insufficiency. Reversible, nonspecific ST-T wave electrocardiographic changes occur in 30% to 90% of patients.

The hypotensive effect of minoxidil may last for days after drug discontinuation.

The mechanism of minoxidil-associated angina is not known. Theories include a coronary "steal" phenomenon secondary to coronary vasodilation, resulting in relative ischemia to hypoperfused areas of myocardium and increased cardiac work secondary to minoxidil-induced reflex tachycardia.

Nonspecific ST-T wave changes are not necessarily associated with cardiac disease.

The incidence of pericardial effusion in minoxidil-treated uremic patients is greater than that expected in non-treated uremic patients. Tamponade is reported in up to 23% of minoxidil-associated pericardial effusions, which has been fatal in rare cases.

Rare cases of pulmonary hypertension have been associated with minoxidil. Pulmonary hypertension is thought to be due to a minoxidil-induced increase in cardiac output and in pulmonary blood flow.

Hemorrhagic and degenerative lesions of the right atrium and focal necrosis of the left ventricular papillary muscle have been described in dog studies, but not in monkeys. No data are available in humans.

Dermatologic

Hypertrichosis usually presents as elongated and hyperpigmented new hair. Hypertrichosis is reversible. Hypertrichosis usually begins at the temples, forehead, and between the eyebrows, but may involve the trunk, extremities, and scalp. Some studies have shown hypertrichosis to occur at lower doses in females, although it may be that females were more distressed by this side effect, and presented these findings earlier than men did.

Dermatologic side effects are common. Hypertrichosis occurs in 30% to 80% of patients within the first 3 to 6 weeks of therapy. A fatal case of toxic epidermal necrolysis has also been reported.

Hypersensitivity

Hypersensitivity reactions such as contact dermatitis, desquamative and bullous rashes, and Stevens-Johnson syndrome have been reported in less than 1% of patients.

Gastrointestinal

Gastrointestinal side effects are uncommon and include nausea and vomiting.

Hematologic

Hematologic side effects, such as decreased hematocrit and hemoglobin, are usually related to dilution from minoxidil-induced sodium and water retention.

A case of thrombocytopenia associated with minoxidil, which recurred upon rechallenge, has been reported.

Nervous system

A case of bilateral optic neuritis, followed by atrophy and vision loss, was associated with minoxidil, despite the fact that the patient was taking other medications as well.

Nervous system side effects are usually limited to headache in approximately 6% and dizziness in approximately 2% of patients. Rare cases of general fatigue have been reported.

Immunologic

Immunologic side effects are extremely rare.

A case of a lupus syndrome associated with the development of a speckled ANA pattern has been associated with minoxidil. The patient had previously taken hydralazine, but did not test positive for ANA until after minoxidil was substituted for hydralazine.

Endocrine

Endocrine side effects include at least one case of pseudoacromegaly. A case of pseudoacromegaly which resulted from long-term (10 years) use of minoxidil (50 mg/day) has been reported.

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