Spironolactone

Female pattern hair loss

• Werachattawatchai 2025 was a 24-week randomized double-blind placebo-controlled pilot trial in 48 premenopausal Thai women. All women also used minoxidil 3 percent solution. Terminal hair count rose 9.48 hairs per square centimeter with spironolactone 100 mg a day against 5.32 with placebo (p=0.063), and moderate-to-marked improvement was rated in 38 against 9 percent (p=0.034) (PMID: 40978669).
• Jha 2026 was a 24-week randomized double-blind trial in 204 women in India. Bicalutamide 50 mg a day produced larger gains in hair count and shaft diameter than spironolactone 100 mg a day on dermoscopy, with no significant difference in clinical endpoints (PMID: 41742379).
• Liang 2022 was a 24-week randomized evaluator-blinded trial in 120 premenopausal Chinese women. Hair density rose more with topical minoxidil plus oral spironolactone than with minoxidil alone (p=0.009), but less than with minoxidil plus microneedling (PMID: 35899211).
• Sadeghzadeh Bazargan 2024 was a blinded randomized trial in 60 Iranian women. Topical minoxidil with spironolactone 100 mg a day scored better than topical minoxidil with finasteride 5 mg a day on physician satisfaction at 4 months, but not in the subgroup with the female hair-loss pattern (PMID: 37650533); see BodyHackGuide's finasteride and minoxidil guides.
• Sinclair 2005 was an open before-and-after study of 80 women over at least 12 months. Forty women took spironolactone 200 mg a day and forty took cyproterone acetate; results were pooled because they did not differ: 44 percent had regrowth, 44 percent no clear change and 12 percent continued loss (PMID: 15787815).
• Sinclair 2018 was a 12-month uncontrolled observational pilot in 100 women. A once-daily capsule of minoxidil 0.25 mg and spironolactone 25 mg was followed by lower hair-loss severity and shedding scores, no hyperkalemia, and 2 women stopping for hives (PMID: 29231239).
• In a 2023 systematic review of 7 studies with 618 patients (414 treated with spironolactone), the reviewers found benefit with oral and topical forms but called for higher-quality randomized trials (PMID: 36923692), and a 2023 meta-analysis reported improvement in 56.6 percent overall (PMID: 37719557). A 2016 Cochrane review of female pattern hair loss called for randomized trials of spironolactone (PMID: 27225981).
• A phase 2 trial planned for 40 women comparing spironolactone tablets with minoxidil lotion at the University of British Columbia is listed in the registry as completed in March 2009, with no results posted (ClinicalTrials.gov NCT00175617).

Two of the open studies above come from Rodney Sinclair's group in Melbourne (PMID: 15787815, PMID: 29231239).

Topical spironolactone

In a 78-patient randomized trial in Iran, a 5 percent spironolactone gel lowered total acne lesion counts more than placebo (p=0.007), but the difference in the acne severity index was not statistically significant (p=0.052) (PMID: 20964565). A 2023 systematic review of 5 topical acne trials with 195 patients reported fewer lesions with topical spironolactone and rated two trials at high risk of bias and three with some concerns (PMID: 36412248).

Safety research in dermatology patients

Several of the dermatology safety studies come from John Barbieri and Arash Mostaghimi at Brigham and Women's Hospital in Boston (PMID: 25796182, PMID: 33502462, PMID: 35138351, PMID: 41655839, PMID: 41654020). In 108,547 women aged 12 to 45 treated for acne from 2008 to 2018, potassium testing within 180 days of starting spironolactone fell only from 41.4 to 38.5 percent despite evidence of low usefulness (PMID: 33502462). In 432 women taking spironolactone with low-dose oral minoxidil for hair loss, adverse effects occurred in 37.7 percent, most often unwanted hair growth (12.3 percent) and dizziness or orthostatic symptoms (12.0 percent) (PMID: 41654020).

Heart failure trial behind the label

• RALES (Pitt 1999) was a double-blind trial in 1,663 patients with severe heart failure. Spironolactone 25 mg a day lowered deaths from 46 to 35 percent (relative risk 0.70) and was stopped early for benefit (PMID: 10471456).

Potassium

The US label warns that spironolactone can cause hyperkalemia, with higher risk in people with impaired kidney function and in those taking potassium supplements, potassium-containing salt substitutes or drugs such as ACE inhibitors and angiotensin receptor blockers (US prescribing information for Aldactone). Among 974 healthy young women taking spironolactone for acne, 13 of 1,802 potassium measurements (0.72 percent) were high, equivalent to the 0.76 percent background rate, and the authors concluded that routine monitoring was unnecessary in this group (PMID: 25796182). Among 398 women aged 45 or older taking spironolactone for skin conditions, high potassium occurred in 10.1 percent, and in 22.4 percent of those aged 65 or older; it was mild in 97.5 percent of cases (PMID: 41655839). After the RALES heart failure trial was published, spironolactone prescriptions and hospital admissions for hyperkalemia rose sharply among older Ontario patients with heart failure who were also taking ACE inhibitors (PMID: 15295047).

Breast and hormonal effects

In RALES, breast enlargement (gynecomastia) or breast pain occurred in 10 percent of men on spironolactone against 1 percent on placebo (PMID: 10471456). The current US label lists irregular menses or amenorrhea, postmenopausal bleeding, breast and nipple pain, decreased libido and trouble achieving or keeping an erection among reported reactions (US prescribing information for Aldactone).

Cancer questions

Older Aldactone labels carried a boxed warning based on tumors in rats fed spironolactone in the diet for 18 to 24 months, among them benign thyroid and testicular adenomas, liver changes, and thyroid follicular adenomas and carcinomas (US prescribing information for Aldactone). In a 2022 meta-analysis of seven studies with about 4.5 million people, most of them older adults, spironolactone use was not associated with breast cancer (risk ratio 1.04) and was associated with less prostate cancer (risk ratio 0.79), with very low certainty of evidence (PMID: 35138351). Among breast cancer survivors in a US insurance database, spironolactone was not associated with cancer recurrence after propensity matching (adjusted hazard ratio 0.966) (PMID: 32446820).

Other reported reactions

The current US label also lists gastric bleeding and ulcers, low white cell and platelet counts, severe skin reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis and DRESS), confusion, dizziness, hair loss (alopecia), and a very few cases of mixed liver injury with one death (US prescribing information for Aldactone).