Key points
- ◆Prolongs the growth phase of the hair and increases its calibre.
- ◆Available in topical form (2-5%) and low-dose oral form under medical supervision.
- ◆A transient increase in shedding at the start is expected and should not cause alarm.
- ◆It needs the enzyme sulfotransferase to become active, which explains the variability in response.
- ◆Results require consistency and are maintained while treatment lasts.
Description
Minoxidil is a drug originally developed as an oral antihypertensive, but whose side effect — increased hair growth — led to its use in the treatment of alopecia. Today it is used mainly in topical formulation (lotion or foam) and, increasingly, in low-dose oral form under medical supervision.
Indications
- Androgenetic alopecia in men and women (topical 2% or 5%).
- Other non-scarring alopecias (telogen effluvium; alopecia areata as an adjuvant).
- Low-dose oral minoxidil (off-label) when the topical form is not tolerated or is insufficient.
Mechanism of action
Minoxidil acts as a vasodilator by opening ATP-dependent potassium channels. At the hair follicle it prolongs the growth (anagen) phase, shortens the shedding (telogen) phase and increases the calibre of the hair.
To be active it needs to be converted into minoxidil sulfate by the enzyme sulfotransferase present in the follicle. The amount of this enzyme varies from person to person, which explains why the response to treatment is not the same in all patients.
Mechanism of action
As a potassium-channel opener, it improves blood flow and prolongs the hair growth phase.
Usual dosage
Topical: 1 ml of solution twice a day, or one daily application of 5% foam, on the dry scalp. Oral (low dose): between 0.25 and 5 mg/day, always under prescription and medical supervision.
A transient increase in shedding during the first 2 to 8 weeks is normal. Results are assessed from 3 to 6 months of consistent use.
Side effects
With the topical form: irritation, itching, scaling or contact dermatitis (often due to propylene glycol) and increased facial hair in women. With the oral form the following may appear:
- Hypertrichosis (increased body hair).
- Oedema and fluid retention.
- Tachycardia or a drop in blood pressure; very rarely, pericardial effusion at high doses.
Contraindications
- Hypersensitivity to minoxidil or the excipients.
- Caution in patients with cardiovascular disease (especially with the oral form).
- Phaeochromocytoma.
Pregnancy and breastfeeding
Its use is not recommended during pregnancy or breastfeeding, since minoxidil is excreted in breast milk and there are insufficient safety data.
Important interactions
The main interaction is with other vasodilator or antihypertensive drugs, as it can potentiate the drop in blood pressure. With the oral form, the combination with diuretics and other antihypertensives should be monitored.
Level of scientific evidence
Level of evidence: high for topical minoxidil in androgenetic alopecia, supported by multiple clinical trials. The evidence for low-dose oral minoxidil is more recent but growing and very favourable, although its use is still considered off-label.
Frequently asked questions
Why does more hair fall out when I start minoxidil?
It is the so-called 'shedding': the drug synchronises the hair cycle and causes old hair to fall out to make way for new hair. It usually lasts a few weeks and is a sign that it is working.
Is oral minoxidil better than topical?
Not necessarily. The low-dose oral form is a useful alternative when the topical form is not tolerated or is inconvenient, but it requires medical assessment and follow-up.
Can I stop using it once I recover my hair?
No. On stopping, the hair gained tends to be lost within a few months, since minoxidil does not correct the cause of the alopecia.
Can women use it?
Yes, it is one of the reference treatments for female alopecia, usually as topical 2% or in low oral doses under medical supervision.
References
- Suchonwanit P, et al. Minoxidil and its use in hair disorders: a review. Drug Des Devel Ther. 2019.
- Randolph M, Tosti A. Oral minoxidil treatment for hair loss: a review. J Am Acad Dermatol. 2021.
- Kanti V, et al. Evidence-based (S3) guideline for the treatment of androgenetic alopecia. J Eur Acad Dermatol Venereol (EADV). 2018. doi:10.1111/jdv.14624.
- Gupta AK, et al. Efficacy of topical minoxidil in androgenetic alopecia: a meta-analysis. 2022.
Clínica Valorian's view
At Clínica Valorian, minoxidil is one of the fundamental tools against alopecia, in both men and women. We choose the route (topical or low-dose oral) according to each patient's profile, tolerance and preferences. We always explain that the initial shedding is normal and that consistency is the key to success.
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This fact sheet is for information and medical education purposes only. It does not replace a medical consultation or an individual prescription.