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Pharmacologic class: Peripheral vasodilator (direct-acting)
Therapeutic class: Antihypertensive, hair growth stimulant
Pregnancy risk category C
FDA Box Warning
• Drug may cause serious adverse effects (such as pericardial effusion occasionally progressing to tamponade) and may exacerbate angina pectoris. Reserve it for hypertensive patients who respond inadequately to maximum therapeutic doses of diuretic and two other antihypertensives.
• Give under close supervision, usually concurrently with therapeutic doses of beta blocker to prevent tachycardia and increased myocardial workload. Usually, drug also must be given with diuretic to prevent serious fluid accumulation. Patients with malignant hypertension and those already receiving guanethidine should be hospitalized when therapy begins so they can be monitored to avoid too rapid, or large orthostatic, blood pressure decreases.
Reduces blood pressure by relaxing vascular smooth muscle, causing vasodilation. Action in hair growth stimulation unclear; vasodilatory action may enhance microcirculation around hair follicles.
Tablets: 2.5 mg, 10 mg
Topical solution: 2%, 5%
Indications and dosages
➣ Severe symptomatic hypertension; hypertension associated with end-organ damage
Adults and children ages 12 and older: 5 mg/day as a single dose, increased carefully q 3 days. Usual range is 10 to 40 mg/day in single or divided doses. For rapid blood pressure control with careful monitoring, dosage may be adjusted q 6 hr. Maximum dosage is 100 mg/day.
Children younger than age 12: 0.2 mg/kg/day P.O. as a single dose. May increase in increments of 50% to 100% until blood pressure control is optimal. Usual range is 0.25 to 1 mg/kg/day; maximum recommended dosage is 50 mg/day.
➣ Male-pattern baldness; diffuse hair loss or thinning in women; adjunct to hair transplantation
Adults: Apply 1 ml of 2% or 5% topical solution to affected area b.i.d. for 4 months or longer.
➣ Alopecia areata
Adults: Apply 1 ml of 2% or 5% topical solution to scalp b.i.d.
• Hypersensitivity to drug or its components
• Dissecting aortic aneurysm
Use cautiously in:
• recent MI, malignant hypertension, heart failure, angina pectoris, severe renal impairment
• concurrent guanethidine therapy
• pregnant or breastfeeding patients.
• Give oral form with meals to decrease GI upset.
☞ If patient is also receiving guanethidine, discontinue that drug 1 to 3 days before starting minoxidil, to avoid severe orthostatic hypotension.
• Know that oral form is usually given with a beta-adrenergic blocker or diuretic to control hypertension.
CV: ECG changes (such as T-wave changes), tachycardia, angina, pericardial effusion, cardiac tamponade, heart failure
GI: nausea, vomiting
Respiratory: pulmonary edema
Other: weight gain, edema
Drug-drug. Antihypertensives, nitrates: additive hypotension
Guanethidine: severe orthostatic hypotension
Nonsteroidal anti-inflammatory drugs: decreased minoxidil efficacy
Drug-diagnostic tests. Alkaline phosphatase, blood urea nitrogen, creatinine, plasma renin activity, sodium: increased levels
Hematocrit, hemoglobin, red blood cells: decreased levels
• Monitor vital signs and ECG.
• Assess daily weight and fluid intake and output.
☞ Monitor cardiovascular status carefully. Stay alert for signs and symptoms of heart failure.
• Watch for hypertrichosis.
• Know that hematologic and renal values usually return to pretreatment levels with continued therapy.
• Instruct patient to take oral form with meals to decrease GI upset.
• Advise patient to weigh himself daily and report sudden gains.
• Tell patient taking oral form that drug may darken, lengthen, and thicken body hair. Tell him to shave or use depilatory to reduce unwanted hair growth. Reassure him that unwanted growth will disappear 1 to 6 months after he stops taking drug.
☞ Instruct patient to immediately report difficulty breathing (especially when lying down) or pain in chest, arm, or shoulder.
• Teach patient how to use topical form. Urge him to read package insert carefully.
• Caution patient not to use topical form on other body parts and not to let it contact mucous membranes.
• Tell patient using topical form that new scalp hair will be soft and barely visible. Caution him to use only 1 ml twice daily, regardless of amount of balding. Remind him not to stop using drug suddenly, because new hair growth will be lost.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs and tests mentioned above.