Side Effects of Rogaine (minoxidil)

Minoxidil is a vasodilator used to treat male-pattern baldness and in women, it is used to treat diffuse loss of hair or thinning of hair in the frontal areas of the scalp. 

Oral minoxidil was originally used for treating high blood pressure, but patients and health care providers noticed hair growth was a side effect of treatment. This led to the development of topical (solution applied to the skin) minoxidil for the treatment of male-pattern baldness. 

The mechanism of action leading to growth of hair is unknown. Rogaine (for men or women) is a brand name available for minoxidil.

Common side effects of minoxidil include

• irritation of the skin,
• itching,
• contact dermatitis, and
• dryness of the scalp or flaking.

Serious side effects of minoxidil include

• headaches,
• dizziness,
• fainting,
• lightheadedness,
• chest pain, and
• increased or decreased blood pressure. 

An increase in the absorption of minoxidil from the scalp can occur in patients with damaged skin, leading to increased side effects. Minoxidil contains alcohol that can irritate the eyes. Tendonitis has also been reported.

Drug interactions of minoxidil include other topical medications, because they may increase the absorption and side effects of minoxidil. 

Minoxidil should not be used in pregnancy because it has not been studied adequately in pregnant women. Minoxidil should not be used by nursing women because it has not been evaluated adequately in breastfeeding mothers.

Common side effects of minoxidil include:

• irritation of the skin,
• itching,
• contact dermatitis, and
• dryness of the scalp or flaking.

Other side effects include:

• headaches,
• dizziness,
• fainting,
• lightheadedness,
• chest pain, and
• increased or decreased blood pressure.

An increase in the absorption of minoxidil from the scalp can occur in patients with damaged skin, leading to increased side effects. Minoxidil's contains alcohol that can irritate the eyes. In case of accidental contact with eyes or other sensitive areas, the exposed area should be washed with cool water. Tendonitis has also been reported.

• Salt and Water Retention—Temporary edema developed in 7% of patients who were not edematous at the start of therapy.
• Pericarditis, Pericardial Effusion, and Tamponade.
• Dermatologic—Hypertrichosis-Elongation, thickening, and enhanced pigmentation of fine body hair are seen in about 80% of patients taking minoxidil (minoxidil (minoxidil (minoxidil tablets) tablets) tablets) tablets. This develops within 3 to 6 weeks after starting therapy. It is usually first noticed on the temples, between the eyebrows, between the hairline and the eyebrows, or in the side-burn area of the upper lateral cheek, later extending to the back, arms, legs, and scalp. Upon discontinuation of minoxidil (minoxidil (minoxidil (minoxidil tablets) tablets) tablets) , new hair growth stops, but 1 to 6 months may be required for restoration to pretreatment appearance. No endocrine abnormalities have been found to explain the abnormal hair growth; thus, it is hypertrichosis without virilism. Hair growth is especially disturbing to children and women and such patients should be thoroughly informed about this effect before therapy with minoxidil (minoxidil (minoxidil (minoxidil tablets) tablets) tablets) is begun. Allergic-Rashes have been reported, including rare reports of bullous eruptions, and Stevens-Johnson Syndrome.
• Hematologic—Thrombocytopenia and leukopenia (WBC < 3000/mm³) have rarely been reported.
• Gastrointestinal—Nausea and/or vomiting has been reported. In clinical trials the incidence of nausea and vomiting associated with the underlying disease has shown a decrease from pretrial levels.
• Miscellaneous—Breast tenderness-This developed in less than 1% of patients.
• Altered Laboratory Findings—
  • (a) ECG changes-Changes in direction and magnitude of the ECG T-waves occur in approximately 60% of patients treated with minoxidil (minoxidil (minoxidil (minoxidil tablets) tablets) tablets). In rare instances a large negative amplitude of the T-wave may encroach upon the S-T segment, but the S-T segment is not independently altered. These changes usually disappear with continuance of treatment and revert to the pretreatment state if minoxidil (minoxidil (minoxidil (minoxidil tablets) tablets) tablets) is discontinued. No symptoms have been associated with these changes, nor have there been alterations in blood cell counts or in plasma enzymeconcentrations that would suggest myocardial damage. Long-term treatment of patients manifesting such changes has provided no evidence of deteriorating cardiac function. At present the changes appear to be nonspecific and without identifiable clinical significance.
  • (b)-Effects of hemodilution-hematocrit, hemoglobin and erythrocyte count usually fall about 7% initially and then recover to pretreatment levels.
  • (c) Other-Alkaline phosphatase increased varyingly without other evidence of liver or bone abnormality. Serum creatinine increased an average of 6% and BUN slightly more, but later declined to pretreatment levels.

Guanethidine

Although minoxidil does not itself cause orthostatic hypotension, its administration to patients already receiving guanethidine can result in profound orthostatic effects. If at all possible, guanethidine should be discontinued well before minoxidil is begun. Where this is not possible, minoxidil therapy should be started in the hospital and the patient should remain institutionalized until severe orthostatic effects are no longer present or the patient has learned to avoid activities that provoke them.