Yes: Tablet

Topical Skin Product; Vasodilator

Management of severe hypertension (usually in combination with a diuretic and beta-blocker); treatment of male pattern baldness (alopecia androgenetica)

C

Hypersensitivity to minoxidil or any component; pheochromocytoma; acute MI; dissecting aortic aneurysm

Maximum therapeutic doses of a diuretic and two antihypertensives should be used before this drug is ever added. It can cause pericardial effusion, tamponade, or exacerbate angina pectoris. Monitor patients who are receiving guanethidine concurrently (orthostasis can be problematic). May need to add a diuretic to minimize fluid gain and a beta-blocker (if no contraindications) to treat tachycardia. Rapid control of blood pressure can lead to syncope, CVA, MI, ischemia. Hypersensitivity reactions occur rarely. Avoid use for a month after acute MI. Inform patients of hair growth patterns before initiating therapy. May take 1-6 months for hypertrichosis to reverse itself after discontinuation of the drug. Use with caution in patients with pulmonary hypertension, significant renal failure, CHF, or ischemic disease. Renal failure and dialysis patients may require a smaller dose.

Oral: Incidence of reactions not always reported.

Cardiovascular: Peripheral edema (7%), sodium and water retention, congestive heart failure, tachycardia, angina pectoris, pericardial effusion with or without tamponade, pericarditis, EKG changes (T-wave changes, 60%), rebound hypertension (in children after a gradual withdrawal)

Central nervous system: Headache (rare), fatigue

Dermatologic: Hypertrichosis (common, 80%), transient pruritus, changes in pigmentation (rare), serosanguineous bullae (rare), rash (rare), Stevens-Johnson syndrome

Endocrine & metabolic: Breast tenderness (rare, <1%), gynecomastia (rare), polymenorrhea (rare)

Gastrointestinal: Weight gain, nausea (rare), vomiting

Hematologic: Intermittent claudication (rare), thrombocytopenia (rare), decreased hematocrit (hemodilution), decreased hemoglobin (hemodilution), decreased erythrocyte count (hemodilution), leukopenia (rare)

Hepatic: Increased alkaline phosphatase

Renal: Transient increase in serum BUN and creatinine

Respiratory: Pulmonary edema

Topical: Incidence of adverse events is not always reported.

Cardiovascular: Increased left ventricular end-diastolic volume, increased cardiac output, increased left ventricular mass, dizziness, tachycardia, edema, transient chest pain, palpitation, increase or decrease in blood pressure, increase or decrease in pulse rate (1.5%, placebo 1.6%)

Central nervous system: Headache, dizziness, weakness, taste alterations, faintness, light-headedness (3.4%, placebo 3.5%), vertigo (1.2%, placebo 1.2%), anxiety (rare), mental depression (rare), fatigue (rare 0.4%, placebo 1%)

Dermatologic: Local irritation, dryness, erythema, allergic contact dermatitis (7.4%, placebo 5.4%), pruritus, scaling/flaking, eczema, seborrhea, papular rash, folliculitis, local erythema, flushing, exacerbation of hair loss, alopecia, hypertrichosis, increased hair growth outside the area of application (face, beard, eyebrows, ear, arm)

Endocrine & metabolic: Menstrual changes, breast symptoms (0.5%, placebo 0.5%)

Gastrointestinal: Diarrhea, nausea, vomiting (4.3%, placebo 6.6%), weight gain (1.2%, placebo 1.3%)

Genitourinary: Urinary tract infections (rare), renal calculi (rare), urethritis (rare), prostatitis (rare), epididymitis (rare), impotence (rare)

Hematologic: Lymphadenopathy, thrombocytopenia, anemia (0.3%, placebo 0.6%)

Neuromuscular & skeletal: Fractures, back pain, retrosternal chest pain of muscular origin, tendonitis (2.6%, placebo 2.2%)

Ocular: Conjunctivitis, visual disturbances, decreased visual acuity

Respiratory: Bronchitis, upper respiratory infections, sinusitis (7.2%, placebo 8.6%)

Symptoms of overdose include hypotension, tachycardia, headache, nausea, dizziness, weakness syncope, warm flushed skin and palpitations; lethargy and ataxia may occur in children

Hypotension usually responds to I.V. fluids, Trendelenburg positioning or vasoconstrictor; treatment is primarily supportive and symptomatic

Guanethidine can cause severe orthostasis; avoid concurrent use - discontinue 1-3 weeks prior to initiating minoxidil.

Antihypertensives: Effects may be additive.

Produces vasodilation by directly relaxing arteriolar smooth muscle, with little effect on veins; effects may be mediated by cyclic AMP; stimulation of hair growth is secondary to vasodilation, increased cutaneous blood flow and stimulation of resting hair follicles

Onset of hypotensive effect: Oral: Within 30 minutes

Peak effect: Within 2-8 hours

Duration: Up to 2-5 days

Protein binding: None

Metabolism: 88% primarily via glucuronidation

Bioavailability: Oral: 90%

Half-life: Adults: 3.5-4.2 hours

Elimination: 12% excreted unchanged in urine

Children <12 years: Hypertension: Oral: Initial: 0.1-0.2 mg/kg once daily; maximum: 5 mg/day; increase gradually every 3 days; usual dosage: 0.25-1 mg/kg/day in 1-2 divided doses; maximum: 50 mg/day

Children >12 years and Adults:

Hypertension: Oral: Initial: 5 mg once daily, increase gradually every 3 days; usual dose: 10-40 mg/day in 1-2 divided doses; maximum: 100 mg/day

Alopecia: Topical: Apply twice daily; 4 months of therapy may be necessary for hair growth.

Elderly: Initial: 2.5 mg once daily; increase gradually.

Note: Dosage adjustment is needed when added to concomitant therapy.

Dialysis: Supplemental dose is not necessary via hemo- or peritoneal dialysis.

Avoid natural licorice (causes sodium and water retention and increases potassium loss)

Blood pressure, standing and sitting/supine; fluid and electrolyte balance and body weight should be monitored

Widespread use of topical minoxidil for hair growth has been made possible by the availability of minoxidil solutions over-the-counter. An increased concentration strength (5% solution) for use by men only may result in some systemic absorption of minoxidil. Note that when minoxidil is used orally, it may cause pericardial effusion. Minoxidil when used in patients with hypertension will not cause regression of left ventricular hypertrophy.

May cause dizziness

May rarely cause leukopenia; use caution with clozapine and carbamazepine

No information available to require special precautions

No effects or complications reported

Topical product must be used every day. Hair growth usually takes 4 months. Notify physician if any of the following occur: Heart rate greater than or equal to 20 beats per minute over normal; rapid weight gain >5 lb (2 kg); unusual swelling of extremities, face, or abdomen; breathing difficulty, especially when lying down; rise slowly from prolonged lying or sitting; new or aggravated angina symptoms (chest, arm, or shoulder pain); severe indigestion; dizziness, lightheadedness, or fainting; nausea or vomiting may occur. Do not make up for missed doses.

May cause hirsutism or hypertrichosis; observe for fluid retention and orthostatic hypotension

Solution, topical: 2% [20 mg/metered dose] (60 mL); 5% [50 mg/metered dose] (60 mL)

Tablet: 2.5 mg, 10 mg

Allon M, Hall D, and Macon EJ, "Prolonged Hypotension After Initial Minoxidil Dose," Arch Intern Med, 1986, 146(10):2075-6.

Isles C, Mackay A, Barton PJ, et al, "Accidental Overdosage of Minoxidil in a Child," Lancet, 1981, 1(8211):97.

Linas SL and Nies AS, "Minoxidil," Ann Intern Med, 1981, 94(1):61-5.

McCormick MA, Forman MH, and Manoguerra AS, "Severe Toxicity From Ingestion of a Topical Minoxidil Preparation," Am J Emerg Med, 1989, 7(4):419-21.

Poff SW and Rose SR, "Minoxidil Overdose With ECG Changes: Case Report and Review," J Emerg Med, 1992, 10(1):53-7.