Minoxidil

A to Z Drug Facts

(min-OX-ih-dill)

Loniten, Minoxidil for Men, Rogaine,  APO-Gain Topical Solution, Gen-Minoxidil, Minoxigaine

Class: Antihypertensive; topical hair growth

 Action Directly dilates vascular smooth muscle by mechanism possibly related to blockade of calcium uptake or stimulation of catecholamine release; reduces elevated systolic and diastolic BP by decreasing peripheral arteriolar resistance; riggers sympathetic, vagal inhibitory and renal homeostatic mechanisms including increased renin release, which results in increased cardiac rate and output and fluid retention; stimulates hair growth by unknown mechanism but likely is related to its arterial vasodilating action.

 Indications

Oral form: Management of severe hypertension associated with target organ damage in patients who have failed to respond to maximum doses of other antihypertensive agents. Topical form: Treatment of androgenic alopecia. Unlabeled use(s): Topical form: Treatment of alopecia areata.

 Contraindications Pheochromocytoma; acute MI; dissecting aortic aneurysm.

 Route/Dosage

ADULTS & CHILDREN > 12 YR: PO 5 mg/day initially. If necessary, can increase to 10–40 mg/day in single or divided doses (maximum 100 mg/day). CHILDREN < 12 YR: PO 0.2 mg/kg/day as single dose initially. May increase in 50%–100% increments until optimal BP control is achieved (usually 0.25–1 mg/kg/day; maximum 50 mg/day). ADULTS: Topical Apply 1 ml to affected scalp areas morning and evening (maximum 2 ml/day).

 Interactions

Guanethidine: May result in profound orthostatic hypotensive effects; discontinue guanethidine before minoxidil therapy. Topical corticosteroids or retinoids, petrolatum: May enhance cutaneous drug absorption of topically applied minoxidil.

 Lab Test Interferences None well documented.

 Adverse Reactions

CV: Topical form: Edema; chest pain; BP changes; palpitations; eart rate changes. Systemic form: Tachycardia; edema; pericardial effusion leading to tamponade; angina; changes in T waves; rebound hypertension following withdrawal. CNS: Systemic form: Headache; fatigue. CNS: Topical form: Headache; dizziness; faintness. DERM: Topical form: Irritant or allergic dermatitis; eczema; local erythema; pruritus; dry scalp; exacerbation of hair loss; alopecia. Systemic and topical forms: Hypertrichosis. GI: Diarrhea; nausea; vomiting. HEMA: Systemic form: Hct, Hgb and RBC counts may fall but return to normal. OTHER: Systemic form: Darkening of skin.

 Precautions

Pregnancy: Category C. Lactation: Excreted in breast milk. In general, nursing should not be undertaken. Children: Safety and efficacy not established. Abnormal scalp: Use of topical form of drug may result in increased absorption and systemic effects; avoid use on scalps with decreased integrity. ECG changes: T wave changes may occur; significance unknown. Fluid/electrolytes imbalance: Sodium and water retention occur, leading to edema and possible CHF. Heart disease: Patients may be predisposed to cardiovascular side effects. Hypersensitivity: Can occur and is manifested by rash. Pericardial effusion: Has occurred rarely, sometimes with tamponade. Renal impairment: Dosage reduction required; pericardial effusion more likely. Severe hypertension: Avoid too rapid BP correction. Patients should be hospitalized to monitor carefully. Tachycardia: Can be prevented by concomitant use of beta-blocker or other agent.

 Administration/Storage

• Dry hair and scalp before topical administration.
• Wear gloves to apply topical form.
• Wash hands after topical administration.
• Administer oral form with diuretic to counteract fluid retention and with beta-blocker to counteract tachycardia.
• Give oral medication with meals to minimize GI symptoms.
• Store tablets at room temperature in tightly closed container.
• Store topical solution at room temperature.

 Assessment/Interventions

• Obtain patient history, including drug history and any known allergies. Note renal insufficiency or cardiac disease.
• Perform urinalysis, renal function tests, ECG, chest x-ray and echocardiogram at initiation of therapy. Repeat any tests with abnormal results q 1–3 mo. After stabilization occurs, repeat tests at 6–12 mo intervals.
• Monitor fluid and electrolyte balance and body weight.
• Avoid too rapid control of very severe high BP; syncope, cerebrovascular accidents, MI and ischemia of special sense organs, decreasing hearing and vision, may result.
• Closely supervise patients with renal impairment to prevent cardiac failure or exacerbation of renal failure.
• Observe for tachycardia or angina and report to physician.
• Report patient complaints of nausea, vomiting, diarrhea, dizziness, lightheadedness, rash or skin irritation to physician.
• Observe patients, especially those with renal impairment, closely for signs of pericardial effusion. If condition is suspected, notify physician; ECG must be performed.
• Monitor patients receiving topical therapy for possible systemic effects after 1 mo of therapy and every 6 mo thereafter.
• If systemic effects appear in patients using drug topically, discontinue drug and notify physician.

 Patient/Family Education

• Advise patient not to change dose without physician direction.
• Tell patient that diuretic and beta-blocker are necessary to enhance effectiveness and to decrease side effects of minoxidil.
• Instruct patient to notify physician of heart rate ³ 20 beats/min over normal, rapid weight gain of > 5 lb, unusual swelling, breathing difficulty, angina symptoms, dizziness or lightheadedness.
• Tell patient to report these symptoms to physician: skin irritation, diarrhea, vomiting, rash or other bothersome physical complaints.
• Warn patient taking oral form that enhanced growth and darkening of fine body hair may occur. It may take 1–6 mo to return to pretreatment appearance.
• Inform patient using topical form that 4 mo of continuous use is required before hair growth is seen and that stopping treatment will lead to hair loss within few mo.
• Advise patient using topical form that more frequent applications or use of larger doses will not enhance hair growth and may lead to side effects.
• Inform patient using topical form to expect initial hair growth to be soft, downy, colorless and barely visible and that after further treatment new hair should match other scalp hair.
• Tell patient using topical form not to use it in conjunction with other topical scalp medications, to apply drug only to healthy areas of scalp, not to use if scalp becomes irritated or sunburned and not to use it on other parts of body.
• For topical application, instruct patient to dry head and scalp before application and to wash hands after application.
• Explain that product contains significant amount of alcohol as base. Caution patient to avoid having topical form coming into contact with eyes, mucous membranes or sensitive skin areas. If accidental contact occurs, instruct patient to rinse area with large amounts of cool tap water and to notify physician.

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Copyright © 2003 Facts and Comparisons
David S. Tatro
A to Z Drug Facts