What to Know About Minoxidil

Popular hair loss remedy is also used to treat high blood pressure

In This Article

Minoxidil is a drug used in pill form to treat poorly controlled hypertension (high blood pressure) and as a topical solution to treat male pattern and female pattern baldness.

Minoxidil was developed in the 1950s to treat ulcers but was found to be a powerful vasodilator (a drug able to dilate blood vessels). Early investigations confirmed that minoxidil was not only effective in controlling hypertension but also promoted hair growth, an unexpected finding. After the approval of the drug as an oral hypertensive in 1979, under the brand name Loniten, a topical version of the drug called Rogaine was approved in 1988 for use in treating male pattern baldness.

Since 1997, topical minoxidil has been available over the counter as a generic and under a wide variety of brand names. Oral minoxidil is available only by prescription. Despite the drug's benefits in treating hypertension and hair loss, minoxidil is not appropriate for everyone and may cause significant side effects.

Uses

Minoxidil is available in two distinct formulations—one topical, one oral—with two equally distinct purposes.

Androgenic Alopecia

Topical minoxidil is used to treat androgenic alopecia, a condition that causes hair loss in both men and women. Androgenic alopecia is triggered by an increase in the male hormones testosterone and dihydrotestosterone (DHT), leading to male pattern baldness in men and hair thinning and hairline recession in women.

Androgenic alopecia occurs in people genetically predisposed to the condition, although oral contraceptives, pregnancy, thyroid disease, and polycystic ovary syndrome (PCOS) can also influence androgenic hair loss.

Topical minoxidil is believed to work by causing dilation of blood vessels around hair follicles. Doing so appears to enlarge the follicles themselves, extending the growth phase of hair (called the anagen phase) and allowing more hair to come to the surface.

Minoxidil has not proven effective in treating a specific autoimmune condition called alopecia areata. Unlike androgenic alopecia, alopecia areata is not caused by a hormonal imbalance but by an immune assault on hair follicles, leading to coin-shaped patches of hair loss.

Resistant Hypertension

Oral minoxidil is prescribed to treat resistant hypertension. Resistant hypertension is a serious form of the disease in which the blood pressure remains abnormally raised despite the concurrent use of three antihypertensive drugs of different classes.

Minoxidil is a potassium channel opener that works by altering the electrical activity within smooth muscles, such as those in blood vessels, causing them to relax. Other potassium channel openers include nicorandil used to treat angina and flupirtine used as a muscle relaxant.

Because of its significant and sometimes serious side effects, minoxidil is taken with other drugs able to counteract these effects. It is never taken on its own.

Off-Label Uses

Since the early days of minoxidil use, the oral drug has been used off-label to treat hair loss under the presumption that a pill works "better" than a topical solution.

Most studies have revealed that this is not so, at least in men, and that the side effects (including the excessive growth of hair on other parts of the body) outweigh the risk. On the other hand, some studies have shown that low-dose oral minoxidil may be safe effective in women with androgenic alopecia.

Other drugs used to treat hair loss include Propecia (finasteride), Avodart (dutasteride), and Aldactone (spironolactone).

Before Taking

Both topical minoxidil and oral minoxidil have their appropriate uses. There are some people who are candidates for treatment and others who may be needlessly harmed if exposed to the drug. Among the considerations and limitations:

  • Topical minoxidil can treat male and female androgenic alopecia on the top of the scalp. It has not been shown to be effective in treating a receding hairline, most especially in women.
  • Oral minoxidil should only be used in people who are unable to control hypertension with three antihypertensive drugs (including one diuretic) and either have symptomatic hypertension or are at risk of organ damage due to uncontrolled high blood pressure.

Precautions and Considerations

There are certain conditions under which minoxidil is ever used (absolute contraindication) and others under which the risks may warrant the avoidance of the drug (relative contraindication).

Topical minoxidil is contraindicated for use in people with a shaved scalp, scalp infection, scalp psoriasis, seborrheic dermatitis, or any condition that compromises the skin of the scalp. It should also be used with caution in people with the following health conditions:

Oral minoxidil is contraindicated for use in people with a rare tumor in the adrenal gland known as pheochromocytoma. Doing so may increase tumor secretions, increasing the risk of hypertension and arrhythmia (irregular heartbeats). It should also be used with extreme caution in people with the following health conditions and only if the benefits outweigh the risks:

Anyone with a pre-existing condition or abnormal lab findings at the start of oral minoxidil treatment should undergo routines lab tests (such as a urinalysis, kidney function tests, chest X-ray, or ECG) every one to three months to ensure the condition has not progressed. Once lab findings are stable, lab tests can be conducted every six to 12 months.

Neither oral nor topical minoxidil should be used in people with a known allergy to minoxidil in any of the other ingredients in the drug.

Dosage

The recommended dose of minoxidil varies by the formulation and strength of the drug (as well as the sex of the user with topical formulations).

Topical Minoxidil

Topical minoxidil comes in different formulations for men and women. The men’s versions come in a 5% solution and a 5% foam, while women’s products also come in a and 2% solution and 5% foam.

Although the foam formulations are identical (other than the application instructions), the minoxidil solutions vary not only by strength but also by the addition of propylene glycol in the men's version (which increases scalp penetration).

The recommended dosage of topical minoxidil is as follows:

  • Minoxidil 2% solution: Apply 1 milliliter (mL) twice daily to the center of the affected scalp. Do not wash the hair for 4 hours after application.
  • Minoxidil 5% solution: Apply 1 milliliter (mL) twice daily to the center of the affected scalp. Do not wash the hair for 4 hours after application.
  • Women's minoxidil 5% foam: Gently massage 1/2 capful (roughly 50 mg minoxidil) once daily to the center of the affected scalp.
  • Men's minoxidil 5% foam: Gently massage 1/2 capful (roughly 50 mg minoxidil) twice daily to the center of the affected scalp.

Of all the available formulations, minoxidil 5% solution is by far the strongest. Because it is also the type most likely to cause scalp irritation, it is not recommended for women.

While topical minoxidil is not contraindicated for use in children, androgenic alopecia is uncommon and possibly unlikely given that children do not produce male hormones in significant quantities until puberty. If used, the treatment and dosage must be directed by a doctor.

Oral Minoxidil

Oral minoxidil is available as a 2.5-milligram (mg) and 10-mg white pill. It is scored so that it can be split if necessary. Minoxidil can be used in adults and children (although its effectiveness and safety in children have been understudied).

The prescribing recommendations for oral minoxidil are as follows:

  • For children under 12, the recommended dose is calculated as 0.2 milligrams (mg) per kilogram given in a single daily dose with or without food. Increases in dosages are allowed, up to a maximum of 50 mg per day, to achieve control of the blood pressure.
  • For adults and children 12 and over, the recommended dose is 5 mg given in a single daily dose with or without food. Increases in dosage are allowed, up to a maximum of 100 mg per day, in either a single dose or split doses.

If the supine blood pressure (taken when lying on your back) is under 30 mmHg, minoxidil can be taken in a single dose. If it is 30 mmHg or higher, the daily dose should be divided to maintain a stable concentration of minoxidil in the blood.

How to Take and Store

Both oral minoxidil and topical minoxidil must be used daily as prescribed. If a dose is missed, take it (or apply it) as soon as you remember. If it is near the time for your next dose, simply skip the missed dose and continue as normal. Never double up doses.

Minoxidil should be stored as follows:

  • Topical minoxidil should ideally be kept between 59 F and 86 F (15 C and 30 C). Store minoxidil foam upright, and do not puncture, incinerate, or expose to temperatures over 50 F (122 C).
  • Oral minoxidil should ideally be kept between 68 F and 77 F (20 C and 25 C) in its original, light-resistant container.

Never use minoxidil after its expiration date. Keep out of reach of children or pets.

Side Effects

Both oral minoxidil and topical minoxidil can cause side effects. Not surprisingly, those associated with oral minoxidil tend to be more severe and, in some cases, can be life-threatening.

Common

Many of the common side effects of minoxidil are mild and transient. However, if any of these side effects persist or worsen, let your doctor know.

Topical Minoxidil
  • Skin redness and irritation

  • Flaking and scaling

  • Itchiness

  • Headache

  • Cold-like symptoms (with 2% solution and 5% foams)

  • Flu-like symptoms (with 5% solution)

  • Sneezing and runny nose

  • Sinus infection

  • Acne

Oral Minoxidil
  • Fatigue

  • Bloating

  • Weight gain

  • Nausea and vomiting

  • Excessive abnormal hair growth (hypertrichosis)

  • Flushing and redness

  • Breast tenderness

  • Numbness or tingling of the face, feet, or hands

  • Heart palpitations

Severe

Topical minoxidil is less likely to cause severe side effects, and clinical research has suggested that few users discontinue treatment due to side effects. The common side effects associated with discontinuation were headaches and itchiness.

Oral minoxidil, on the other hand, is known to cause significant and potentially severe side effects. On rare occasions, minoxidil can lead to pericarditis (heart inflammation), pericardial effusion (buildup of fluid in the lining of the heart), cardiac tamponade (compression of the heart due to effusion), kidney failure, and heart failure.

When to Call 911

Call 911 or seek emergency care if you experience the following while on oral minoxidil:

  • Rapid heartbeat (20 beats or more above your normal heart rate)
  • Rapid weight gain of more than 5 pounds (2.3 kilograms)
  • Difficulty breathing, especially when lying down
  • New or worsening of pain in the chest, jaw, arm, or shoulder
  • Dizziness, lightheadedness, or fainting

Warnings and Interactions

Both topical and oral minoxidil are Pregnancy Category C drugs, meaning that animal studies have suggested that fetal harm is possible but there are no well-controlled studies have been conducted in humans. If you are pregnant or planning to get pregnant, speak with your doctor to fully understand the risks and benefits of using minoxidil in any form

It is unknown if minoxidil can be passed in breast milk. Due to the lack of safety research, neither oral nor topical minoxidil should be used if you are breastfeeding.

Interactions

Topical minoxidil is not associated with any drug interactions with systemic drugs (those taken by mouth or intravenously). There are, however, some topical drugs that may increase the absorption of minoxidil and, with it, the risk of side effects:

  • Anthralin (known by the brand names Drithocreme HP, Zithranol, and others)
  • Betamethasone dipropionate 
  • Tretinoin (known by the brand names Retin-A, Refissa, Renova, and others)

Oral minoxidil is known to interact with the antihypertensive drug guanethidine. Taking them together can lead to severe hypotension (low blood pressure), leading in some cases to extreme dizziness, blurry vision, nausea, confusion, and fainting. The drugs should not be taken together. Ideally, guanethidine should be stopped before minoxidil is started.

A Word From Verywell

Minoxidil, like Viagra (sildenafil), is a drug designed for one use that was later found to have another important use. Although they are the same drug molecule, this should not suggest that they can be used interchangeably or that increased doses will afford better results. Always take minoxidil as a prescribed. If the drug does not appear to be working, let your doctor know.

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Article Sources
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