Minoxidil adverse effects

Minoxidil may produce serious adverse effects. It can cause pericardial effusion, occasionally progressing to tamponade it can exacerbate angina pectoris. Reserve for hypertensive patients who do not respond adequately to maximum therapeutic doses of a diuretic and 2 other antihypertensive agents. 

In an open comparative study of androgenetic alopecia in 90 men oral finasteride (1 mg/day for 12 months n = 65) was compared with 5% topical minoxidil solution twice daily (n = 25) (22). The cure rates were 80% for oral finasteride and 52% for topical minoxidil. The adverse effects were all mild, and did not lead to withdrawal of treatment. Of the 65 men given oral finasteride, six had loss of libido, and one had an increase in body hair at other sites irritation of the scalp was seen in one of those who used minoxidil. These adverse events disappeared as soon as the treatment was withdrawn. The laboratory data did not show any statistically or clinically significant changes from baseline values to the endpoint, except for the serum total testosterone concentration, which was increased, and free testosterone and serum prostate-specific antigen in the finasteride group which were reduced from baseline values. 

Although vasodilators are effective in lowering blood pressure, these drugs are associated with a number of adverse effects. Reflex tachycardia often occurs because baroreflex responses attempt to compensate for the fall in vascular resistance that these drugs produce. This side effect is analogous to the increased heart rate occurring when alpha blockers are used to decrease peripheral vascular resistance. Other common reactions include dizziness, postural hypotension, weakness, nausea, fluid retention, and headache. Minoxidil also increases hair growth on the face, ears, forehead,... 

Several older drugs are powerfully vasodilating, but precluded from routine use in hypertension by their adverse effects. Minoxidil and nitroprusside still have special indications. 

Topical minoxidil stimulates new hair growth and arrests loss of hair in androgenic alopecia. Minoxidil is poorly absorbed through the skin (less than 4%) (1), and plasma concentrations of minoxidil are far less than 10% of the mean minoxidil concentration present 2 hours after oral ingestion of 5 mg, the lowest dose for the treatment of hypertension (2). Its adverse effects after topical apph-cation are therefore usually limited to the apphcation site on the scalp. They include irritant contact dermatitis, allergic contact dermatitis, and exacerbation of seborrheic dermatitis. These effects are seen in 5.7% of patients who use a 5% solution and in 1.9% of those who use a 2% formulation (3). 

Local adverse effects of topical minoxidil (usually in an alcohol-propylene glycol base) include dryness, irritation, pruritus, contact allergy (SEDA-11, 139), and photocontact allergy (SEDA-11,139). 

Adverse Effects. The side effects of topical minoxidil are mainly local, caused by skin irritation and contact dermatitis. Systemic side effects are uncommon because of limited percutaneous absorption, but diffuse hypertrichosis of the face and limbs has been reported with the 5% solution and was attributed to systemic absorption of the drug (84). Although topical minoxidil does not change blood pressure in healthy subjects, it increases heart rate by 3-5 beats/min and slightly increases the left ventricular end-diastolic volume, cardiac output, and left ventricular mass (85). These effects are not considered clinically significant, and the potential for cardiovascular side effects is very low. 

ADVERSE EFFECTS AND PRECAUTIONS The adverse effects of minoxidil can be severe and are divided into three major categories fluid and salt retention, cardiovascular effects, and hypertrichosis. 

In experimental animals, minoxidil caused several kinds of myocardial lesions and other adverse cardiac effects (see Warninqs). 

The pattern of adverse vasodilator effects with minoxidil is similar to, but more severe than, that of hydralazine and fluid retention can be troublesome. 

Minoxidil has particularly adverse consequences in hypertensive patients who have left ventricular hypertrophy and diastolic dysfunction. Such poorly compliant ventricles respond subopti-mally to increased volume loads, with a resulting increase in left ventricular filling pressure. This likely contributes to the increased pulmonary artery pressure seen with minoxidil therapy in hypertensive patients and is compounded by the drug-induced retention of salt and water. Cardiac failure can result from minoxidil therapy in such patients the potential for this complication can be reduced but not prevented by effective diuretic therapy. Pericardial effusion is an uncommon but serious complication of minoxidil. Although more commonly described in patients with cardiac failure and renal failure, pericardial effusion can occur in patients with normal cardiovascular and renal function. Mild and asymptomatic pericardial effusion is not an indication for discontinuing minoxidil, but the situation should be monitored closely to avoid progression to tamponade. Effusions usually clear when the drug is discontinued but can recur if treatment with minoxidil is resumed. 

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