Spironolactone

Spironolactone is an orally administered drug, originally a potassium-sparing diuretic (an aldosterone antagonist), which also has an antiandrogen effect. Because of the latter, it is used off-label to treat female pattern hair loss and other signs of hyperandrogenism, such as hirsutism or acne.

• Female pattern hair loss in adult women (off-label use).
• Hirsutism and acne associated with hyperandrogenism.
• Classic approved indications: high blood pressure, heart failure and oedema.

Spironolactone blocks androgen receptors and reduces androgen production, decreasing the hormonal stimulus that promotes follicular miniaturisation in predisposed women. This antiandrogen effect is the basis of its use in hair loss, distinct from its diuretic action.

In female hair loss, the doses used usually range from 50 to 200 mg per day orally, starting low and adjusting according to tolerance. Hair results usually take at least 6-12 months of continuous treatment, and the benefit is maintained while the drug is taken.

The most common adverse effects derive from its diuretic and antiandrogen actions:

• Menstrual changes.
• Breast tenderness or enlargement.
• Dizziness or low blood pressure.
• Increased blood potassium (hyperkalaemia), especially with kidney impairment or certain drugs.

Periodic monitoring of potassium and blood pressure is recommended.

• Pregnancy and women of childbearing age without contraception.
• Severe kidney impairment and hyperkalaemia.
• Addison's disease.
• Hypersensitivity to the active substance.

Spironolactone is contraindicated during pregnancy because of the theoretical risk of feminising the genitals of a male foetus. Effective contraception must be ensured in women of childbearing age. It is not advised during breastfeeding.

It can raise blood potassium if combined with potassium supplements, ACE inhibitors, ARBs or other potassium-sparing diuretics. It may also interact with lithium and some anti-inflammatory drugs. Kidney function should be assessed before and during treatment.

Level of evidence: moderate. Its use in female pattern hair loss is supported by observational studies and clinical experience rather than by large randomised trials. It is considered a widely used off-label treatment in women. A randomised, double-blind trial (2025) compared spironolactone 100 mg/day with bicalutamide 50 mg/day over 24 weeks: bicalutamide showed better trichoscopic parameters, with no significant clinical difference; spironolactone retains the greater experience of use.