Minoxidil

What minoxidil is

Minoxidil was originally a blood pressure drug; increased hair growth is one of the most common side effects of the tablets. In Germany there are two routes today: solutions and foams with up to 5 % for use on the scalp in hereditary hair loss (androgenetic alopecia), and tablets that are approved only for high blood pressure that does not respond adequately to other drugs.

Unlike finasteride, minoxidil does not lower the hormone DHT; according to the summary of product characteristics, the increased hair growth under the tablet is not associated with a hormonal disorder. What is rated is the state of knowledge. For use on the scalp it is good: blinded studies in men and women, decades of use. For the low-dose tablet against hair loss, called “LDOM” in the scene, there is one blinded comparative study, one network meta-analysis and large retrospective analyses.

How it works

As a tablet, minoxidil lowers blood pressure by dilating the small arteries. This is done by its metabolite minoxidil sulfate, which opens potassium channels in the vascular muscle. The body reacts in the opposite direction: heart rate rises, and salt and water are retained. That is why, according to the summary of product characteristics, the tablet for high blood pressure is given together with a diuretic and a beta blocker.

How minoxidil stimulates hair growth is only partly understood despite more than 30 years of use. In animal experiments it shortens the resting phase of hair follicles so that they enter the growth phase earlier, and probably likewise in humans. It presumably also prolongs the growth phase and enlarges the follicles. Whether the same potassium channels play a role in this has not been shown so far.

What the studies show

Olsen 2002: 5 % versus 2 % and placebo

Olsen 2002 (J Am Acad Dermatol) divided 393 men aged 18 to 49 with hereditary hair loss into three groups: 5 % solution (157), 2 % solution (158) or vehicle solution without active ingredient (78), each twice daily for 48 weeks. The 5 % solution was superior to both comparison groups in the number of non-vellus hairs in the target area and in the assessment of participants and investigators, and the response began earlier. Itching and local irritation occurred more often under 5 %; there were no signs of effects elsewhere in the body.

Blume-Peytavi 2011: foam in women

Blume-Peytavi 2011 (J Am Acad Dermatol) compared 5 % foam once daily with 2 % solution twice daily in 113 women over 24 weeks. The foam was non-inferior in hair count and hair thickness, with non-significantly better values, and caused skin intolerance less often, mainly itching and flaking. Because of the different dosage forms, the participants were not blinded.

Penha 2024: tablet versus solution

In a double-blind study at a Brazilian specialist clinic (JAMA Dermatol 2024), 90 men aged 18 to 55 received for 24 weeks either low-dose oral minoxidil plus a solution without active ingredient, or 5 % solution plus a dummy tablet; 68 completed the study. In the density of terminal hairs at the frontal area and crown, the groups did not differ significantly. Only the photo assessment favored the tablet at the crown (24 %, p = 0.04), not at the frontal area. Under the tablet, 49 % developed increased body hair growth (hypertrichosis) and 14 % headaches.

Vañó-Galván 2021: 1,404 patients in retrospect

The largest safety analysis of the low-dose tablet (J Am Acad Dermatol 2021) looks back across several centers at 1,404 patients, two thirds of them women. The most common side effect was hypertrichosis (15.1 %). Lightheadedness (1.7 %), fluid retention (1.3 %), palpitations (0.9 %), headache (0.4 %) and swelling around the eyes (0.3 %) were less common; 1.7 % discontinued because of side effects, and no life-threatening events were observed. The study is retrospective and has no control group.

Where the data stop

• Whether the tablet is better. The only blinded head-to-head comparison with the solution showed no superiority in hair density. The network meta-analysis that puts oral minoxidil ahead compares indirectly across different studies.
• The cardiac safety of the low dose. Pericardial effusion, fluid retention and angina pectoris are known from the treatment of high blood pressure. For the low dose against hair loss there are retrospective analyses without a control group, but no large controlled long-term studies.
• How minoxidil acts on hair. After more than 30 years, the pathway at the follicle is only partly clarified. That potassium channels in the hair follicle are involved is an assumption, not proof.
• Duration. The controlled studies cited ran for 24 to 48 weeks. They do not directly say what happens over many years.

Status, approval and legal

For use on the scalp in hereditary hair loss, minoxidil up to a concentration of 5 % is exempt from the prescription requirement (German Ordinance on Prescription-Only Medicines). As a medicine it remains pharmacy-only, meaning it is available only in pharmacies.

Tablets containing minoxidil are prescription-only. In Germany they are approved only for high blood pressure that does not respond adequately to maximum doses of other blood pressure drugs in combination, and should then be given together with a diuretic and a beta blocker. For hair loss, the tablet is an unapproved use and belongs in the hands of a physician.

Following a European procedure in 2024, the product information for the solutions and foams contains a warning: infants who came into contact with treated skin areas of their parents developed increased body hair growth. The packaging also states that the product must not be taken orally.

Safety

On the scalp, itching and local irritation are the most common side effects, more frequent under 5 % than under 2 %. Children should not come into contact with treated areas; in infants, the increased body hair growth regressed within months after contact ended.

For the tablet, the summary of product characteristics lists pericardial effusion in 3 to 5 % of treated hypertensive patients not on dialysis, occasionally with cardiac tamponade, as well as salt and water retention with edema, reflex tachycardia and possible angina pectoris. Contraindications include pheochromocytoma and pulmonary hypertension due to mitral stenosis. Increased hair growth on the face and body occurs in most hypertensive patients and regresses one to six months after stopping.

These figures come from the treatment of high blood pressure. In the retrospective analysis of the low dose against hair loss, side effects elsewhere in the body were rare; a control group was missing. The safety value of 7 in the BK-Score rates the state of the data, not the danger.

Sources

• Olsen EA et al., J Am Acad Dermatol 2002 – 5 % versus 2 % minoxidil solution and placebo, 393 men, 48 weeks
• Blume-Peytavi U et al., J Am Acad Dermatol 2011 – 5 % foam versus 2 % solution in 113 women
• Penha MA et al., JAMA Dermatol 2024 – oral versus topical minoxidil, randomized study with 90 men
• Gupta AK et al., JAMA Dermatol 2022 – network meta-analysis of minoxidil, finasteride and dutasteride in men
• Vañó-Galván S et al., J Am Acad Dermatol 2021 – safety of low-dose oral minoxidil, 1,404 patients, retrospective
• Messenger AG, Rundegren J, Br J Dermatol 2004 – mechanisms of action of minoxidil on hair
• Summary of product characteristics Lonolox (minoxidil tablets, as of November 2023)
• EMA/CMDh 2024 – minoxidil for use on the skin: hypertrichosis in infants after skin contact (PSUSA/00002067/202310)
• German Ordinance on Prescription-Only Medicines (AMVV), Annex 1 – minoxidil, exempted for topical use in androgenetic alopecia up to 5 %
• German Medicines Act (AMG) § 43 – pharmacy-only requirement