Minoxidil

Minoxidil is one of the best-studied active ingredients against hereditary hair loss. Topically, meaning applied to the scalp, it is approved over the counter in Germany. In addition, minoxidil is available as a capsule to take by mouth (oral minoxidil): a low-dose form that may be an option off-label on prescription, for example when topical application does not help enough or is difficult to fit into everyday life. What is suitable is decided by the doctor. Minoxidil prolongs the growth phase of the hair and only works as long as you use it. The earlier you start, the more can be preserved.

How does minoxidil work?

Minoxidil is used for hereditary hair loss (androgenetic alopecia), the most common form of hair loss in men and women. You can read how this form develops under Understanding hair loss. Originally, the active ingredient did not come onto the market as a hair product but as a medication for high blood pressure. That it stimulates hair growth was noticed as a side effect in blood-pressure patients and was later used specifically for that purpose.¹

Minoxidil belongs to the vasodilators, the active ingredients that widen the blood vessels. However, the exact mechanism at the hair follicle is not conclusively understood. Each hair alternates between a growth phase (anagen) and a resting phase (telogen). It is established that minoxidil opens certain potassium channels at the dermal papilla, the control centre of the hair root, and prolongs the anagen phase.² As a result, resting follicles return to the active phase earlier, so that more hairs grow at the same time and become stronger. That the widened vessels supply the follicles with more oxygen and nutrients is regarded as a possible explanation, but is not proven to be the sole cause of hair growth.

A particular feature explains why minoxidil does not work equally well in everyone. The active ingredient is a precursor and must first be converted in the scalp by the enzyme sulfotransferase into its active form, minoxidil sulfate. How active this enzyme is in the hair follicles differs from person to person. With low enzyme activity, topical application responds less well or not at all, which explains part of the so-called non-responders.³

Important for realistic expectations: minoxidil can strengthen existing, weakened hairs and reactivate resting hair roots. It does not bring back completely dead follicles at already bald spots. This is why treatment works better the earlier it begins.

How is minoxidil used and is it approved?

There are two forms of minoxidil. Topical minoxidil for application to the scalp is approved in Germany for hereditary hair loss and available over the counter in pharmacies. Oral minoxidil, the tablet, is not approved for hair loss in Germany and is only prescribed off-label. For most people, the topical form is therefore the usual route.

In women, the 2 percent concentration is usually used, in men the 5 percent concentration.² How often you apply it depends on the preparation and concentration. The product is applied to the dry scalp in the affected area and stays there, so it is not washed out. After applying, you wash your hands and let the treated area dry.

Oral minoxidil, the tablet, is approved in Germany only for the treatment of high blood pressure, not for hair loss. Its use against hair loss is off-label and prescription-only. Off-label means that an approved medication is prescribed outside its area of application. A doctor may do this if they consider it medically justifiable in an individual case; they weigh benefit and risk.

In pronounced hereditary hair loss, minoxidil is sometimes combined with finasteride, which acts at a different point. Whether a combination makes sense in an individual case is decided by the doctor.

Side effects

The most common with topical use are local reactions on the scalp. Redness, itching, flaking or burning are possible, often triggered by excipients such as propylene glycol.¹ How well a preparation is tolerated also depends on the excipients it contains.

Other possible side effects:

• Unwanted hair growth (hypertrichosis): Increased hair growth can also occur in places other than the scalp, such as the face. With topical use this happens above all when the active ingredient reaches adjacent areas of skin. With the oral form this effect is more common, because the active ingredient acts throughout the whole body.⁴
• Initial increased shedding (shedding): At the start, hair loss can temporarily increase, usually within the first two to eight weeks, sometimes longer. Older hairs are shed so that new ones can grow. This is a known effect and not a sign that the treatment is not working.
• Rare systemic effects: With topical use only a little active ingredient reaches the bloodstream, so systemic side effects are rare. With the oral form, cardiovascular effects such as fluid retention, a faster pulse or dizziness are possible, because minoxidil acts on the circulation.⁴

Interactions and contraindications

Topical minoxidil should not be applied to an irritated, inflamed, injured or sunburned scalp, because more active ingredient can then be absorbed into the body. It must not be used in cases of known hypersensitivity to minoxidil or to one of the excipients.

Because minoxidil was originally a blood-pressure medication, caution is required in cardiovascular disease, especially with the oral form. Anyone taking heart medication or blood-pressure-lowering agents, or who has a heart condition, should have its use clarified with a doctor beforehand. Whether minoxidil is suitable in your case and whether interactions with your other medications can occur is checked by our doctors based on your health information.

Warnings

According to its approval, topical minoxidil should not be used during pregnancy and breastfeeding. The active ingredient can reach the child through the placenta and passes into breast milk. Whether a pregnancy or breastfeeding applies is clarified beforehand in the medical health questionnaire.

Minoxidil is life-threatening for cats and other pets. Even small amounts, for example from licking treated skin, towels or spilled solution, can cause severe heart and circulatory damage in cats and be fatal.⁵ Keep the product out of reach, wash your hands after applying, let the treated area dry, and keep your pet away from pillows and towels that may have residue on them. You can read more in the article Minoxidil and pets.

Also avoid contact with the eyes and mucous membranes. If minoxidil gets into the eye, rinse it out with plenty of water. Results take months, and the effect achieved is reversible: if you stop minoxidil, the effect wears off over several months, and hair loss continues where it would stand without treatment.