Minoxidil

What is the FDA-approved use of minoxidil?

Topical minoxidil is FDA approved as a 2% and 5% strength topical formulation (Rogaine) to treat hair loss in women and men. All other topical compounded strengths of minoxidil are considered off label for hair loss treatment. Oral minoxidil is FDA-approved for symptomatic high blood pressure that is not controlled by a diuretic plus two other blood pressure lowering drugs. Your provider may recommend a low dose of oral minoxidil as an off label hair loss treatment.

Mechanism of Action

Minoxidil acts through multiple pathways (vasodilator, anti-inflammatory agent, inducer of the Wnt/β-catenin signaling pathway, an antiandrogen), and may also affect the length of the anagen and telogen phases.

Who should not use minoxidil?

Do not use Oral minoxidil if:

You have a pheochromocytoma, a tumor in the adrenal gland.
You have a known allergic reaction to oral minoxidil.

Do not use topical minoxidil if:

You have a hypersensitivity to the drug or any of its components including propylene glycol.

Black Box Warning for Serious Cardiac Effects

Oral minoxidil has a black box warning because the medication is a powerful antihypertensive agent and can produce serious adverse effects. Note that serious cardiovascular side effects from oral minoxidil have been demonstrated in clinical trials evaluating patients with symptomatic high blood pressure that was not controlled by a diuretic plus two other blood pressure lowering drugs using oral minoxidil at doses of 5mg or higher. When used off-label for hair loss, oral minoxidil is dosed at less than 5mg in an attempt to avoid blood pressure lowering effects and reduce adverse cardiovascular effects.
Minoxidil can cause pericardial effusion, the accumulation of too much fluid in the sac that surrounds the heart (pericardium). Pericardial effusion can progress to a condition called tamponade which increases pressure on the heart and keeps it from beating properly. This can result in sharp chest pain and difficulty breathing. Seek emergency treatment if this occurs.
When using minoxidil to treat high blood pressure, it should be reserved for patients who do not respond adequately to maximum therapeutic doses of a diuretic (water pill) and two other blood pressure lowering drugs. It must be administered under close supervision, usually along with a beta-blocking agent to prevent increased heart rate (tachycardia) and increased the stress put on the heart muscle (myocardial workload). It must also usually be given with a diuretic to prevent serious fluid accumulation.
Chest pain warning: Minoxidil can increase your heart rate and cause or worsen chest pain. Doctors usually prescribe a beta-adrenergic blocking drug with minoxidil to avoid this. If you have new or worsening pain in the chest, arm, or shoulders, tell your doctor right away.
Heart function warning: Minoxidil can cause poor heart function or worsen existing heart problems like heart failure. When tested on animals, minoxidil caused several kinds of lesions of the heart muscle as well as other adverse heart effects. Patients with malignant hypertension and those already receiving guanethidine should be hospitalized when minoxidil is first administered so that they can be monitored to avoid too rapid or large decreases in blood pressure.

What should I tell my provider before starting minoxidil?

Ensure you disclose your entire medical history to your healthcare provider. Be aware that withholding or providing inaccurate health and medical history to obtain treatment can have serious consequences, potentially including death.

Comorbidities:

Minoxidil should be used with caution in patients with certain conditions. It is advised that you obtain clearance from your cardiologist or primary care doctor prior to beginning oral minoxidil for hair loss therapy.
Do not take this medication and tell your provider if you have a history of:
Heart conditions (such as uncontrolled high blood pressure, heart failure, history of heart attack, pericarditis, abnormal heart rhythm, chest pain/angina)
Vascular conditions (stroke, severe lower leg swelling, pulmonary hypertension)
Kidney disease
Liver disease
Are pregnant or breastfeeding
Do not use topical minoxidil if you have active skin abrasion or irritations, such as excoriations, open wounds, psoriasis, or sunburn. This can increase your risk for skin irritation and side effects from systemic absorption of topically administered Minoxidil.

Pregnancy and Special Populations:

Minoxidil is pregnancy category C, indicating that its safety in pregnant women has not been fully established. It should be avoided by women who are pregnant, planning pregnancy, or breastfeeding unless deemed essential by a physician.
The safety and efficacy of topical Minoxidil products have not been established in children and adolescents. Children should not take or come in contact with Minoxidil. Minoxidil can be toxic to some animals, so do not let your pets come into contact with it or lick your hands after application.

Drug-interactions:

Minoxidil may interact with other medications, especially those that affect blood pressure or heart function. Always inform your healthcare provider of all the medications you are currently taking.
Guanethidine should not be taken with minoxidil.
You may need to limit or reduce the salt in your diet while taking minoxidil.
Do not use potassium supplements or salt substitutes, unless your doctor has told you to.
Do not take minoxidil with sildenafil or tadalafil.

How should I use minoxidil?

Topical minoxidil should be applied to the affected areas of the scalp as directed by your provider. The topical formulation is meant for external use only and should not be ingested or applied to other body parts. Wash your hands thoroughly after application.
Oral minoxidil can be taken with or without meals. You should take oral minoxidil exactly as prescribed and should not change your dosing regimen without discussing it with your provider first.

What side effects should I be aware of with Minoxidil?

Common side effects for topical minoxidil:

Initial shedding or increased hair loss in the first weeks of use.
Itchy scalp or skin rash.
Dryness, scaling, or flakiness of the scalp.
Redness or irritation at the application site.
Unwanted facial or body hair growth, especially in women.
Dizziness or light-headedness.
Rapid or irregular heartbeat.
Chest pain or palpitations.
Swelling of hands, feet, or face.
Difficulty breathing when lying down.
Weight gain due to fluid retention.

Serious side effects of oral minoxidil:

You or a caregiver should carefully monitor for these side effects, especially in the beginning of treatment and with dose changes. If you experience severe symptoms or are having a medical emergency, call 911 or seek immediate medical attention.

Salt and water retention: Monitor for fluid retention and increase in body weight. If you quickly gain five or more pounds, or if there is any swelling or puffiness in the face, hands, ankles, or stomach area, this could be a sign that you are retaining body fluids. Contact your provider immediately.
Increased heart rate (tachycardia): Oral minoxidil can increase your heart rate. Chest pain/angina may worsen or appear for the first time during oral minoxidil therapy, likely due to the increased oxygen demands associated with increased heart rate and cardiac output. You should measure your heart rate by counting your pulse rate while you are resting. If you have an increase of 20 beats or more a minute over your normal pulse or experience new/worsening chest pain, contact your provider immediately or seek urgent care.
Pericarditis, Pericardial Effusion and Tamponade: Oral minoxidil can cause an accumulation of fluids in the sac surrounding the heart. Monitor for sharp pain in the chest, arm, or shoulder; signs of severe indigestion; or shortness of breath, dizziness, lightheadedness, and fainting. These could be signs of serious heart problems and you should seek immediate emergency care.
Hazard of Rapid Control of Blood Pressure: A sudden or too large of a drop in blood pressure can lead to fainting, heart attack, and loss of blood flow to certain organs. These are signs of serious heart problems and you should seek immediate emergency care. You should monitor your blood pressure closely when starting oral minoxidil or changing dosing.

The above does not encompass all potential side effects, medication interactions, or studies related to minoxidil. Unreported or yet undiscovered side effects might exist. Please review the FDA prescribing information and the Prescriber’s Digital Reference (PDR) for a comprehensive overview of minoxidil. https://www.accessdata.fda.gov/drugsatfda_docs/label/2015/018154s026lbl.pdf https://medlineplus.gov/druginfo/meds/a682608.html

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