Spironolactone is a prescription medication primarily known as a potassium-sparing diuretic, used to manage high blood pressure and fluid retention. It is also commonly prescribed for its anti-androgenic effects in women to treat hirsutism. Hirsutism is characterized by excessive growth of dark, coarse hair in a male-like pattern, often appearing on the face, chest, and back. This growth is typically driven by an overabundance or increased sensitivity to androgens, such as testosterone.
Mechanism of Action Against Hair Growth
Spironolactone’s effectiveness against excessive hair growth is rooted in its ability to interfere with androgen signaling pathways. The medication acts as a competitive antagonist, binding to androgen receptors in the skin and hair follicles. By occupying these sites, spironolactone physically blocks potent androgens, such as testosterone and dihydrotestosterone (DHT), from stimulating thick, dark hair growth.
Beyond blocking receptors, spironolactone also reduces the overall production of androgens. It achieves this by inhibiting enzymes involved in hormone synthesis, including 17-alpha-hydroxylase and 17,20-lyase. This dual mechanism—blocking androgen action at the hair follicle and decreasing circulating levels—manages androgen-driven symptoms. It also weakly inhibits 5-alpha-reductase, the enzyme converting testosterone into the more potent DHT within the hair follicle. This combined biological action ultimately leads to a reduction in the density and thickness of terminal hairs.
Typical Usage and Patient Selection
Spironolactone is typically prescribed for women diagnosed with hirsutism, particularly those with Polycystic Ovary Syndrome (PCOS) or idiopathic hirsutism. PCOS is a common endocrine disorder involving elevated androgen levels. Idiopathic hirsutism refers to excessive hair growth without an identifiable hormonal cause, implying heightened sensitivity of the hair follicles to normal androgen levels. The medication is always prescription-only, and its use for hirsutism is considered an off-label application.
Treatment often begins with a low dose, such as 50 milligrams (mg) daily, to assess tolerance and minimize side effects. The dose is then gradually increased, or titrated, based on the patient’s response and tolerability, typically over several months. For hirsutism, the effective maintenance dose range is usually between 100 mg and 200 mg per day, sometimes split into two daily doses. Spironolactone is often prescribed in combination with a combined oral contraceptive to suppress ovarian androgen production and regulate menstrual cycles, which the anti-androgen effects can disrupt.
Expected Results and Treatment Duration
The reduction of facial hair with spironolactone is a slow process requiring consistent use. The hair growth cycle dictates that existing terminal hairs must complete their growth phase and shed before medication effects become apparent. Initial improvements are usually not noticeable until at least six months of continuous treatment.
Significant reduction in hair growth is often observed after 12 months or more. Spironolactone prevents the growth of new, coarse hairs and causes existing hairs to become finer and lighter over time, but it does not remove hair that has already grown. Therefore, it is often used alongside cosmetic treatments like laser hair removal or electrolysis to remove existing hair. Clinical studies indicate that women treated for hirsutism experience a good reduction in hair scores after prolonged therapy.
Important Safety Considerations
Because spironolactone is a potassium-sparing diuretic, a safety consideration is the risk of hyperkalemia, or elevated potassium in the blood. This risk is present in patients with pre-existing kidney impairment or those taking other potassium-increasing medications, such as certain blood pressure drugs. Healthcare providers routinely monitor serum potassium and kidney function, especially when starting the medication or adjusting the dosage.
For women of childbearing age, spironolactone is absolutely contraindicated during pregnancy. Due to its anti-androgen properties, the medication carries a risk of feminizing a male fetus during critical development periods. Sexually active women taking spironolactone must use highly effective contraception methods throughout treatment. Common side effects include menstrual irregularities and breast tenderness, which are generally dose-dependent and can often be managed by adjusting the dosage or adding an oral contraceptive.