Can spironolactone (100 mg daily) used for acne cause uterine fibroids or menstrual irregularities?

Spironolactone and Menstrual Irregularities/Fibroids

Spironolactone at 100 mg daily commonly causes menstrual irregularities (15-30% of patients) but does not cause uterine fibroids. 1

Menstrual Irregularities

Menstrual irregularities are the most common side effect of spironolactone therapy for acne. 1, 2

Incidence and Dose-Dependency

• Menstrual irregularities occur in 15-30% of patients taking spironolactone for acne 1
• At 100 mg daily (the typical starting dose), menstrual irregularities are common but less frequent than at higher doses 1
• The risk increases significantly with dose: women receiving 200 mg/day have a relative risk of 4.12 (95% CI 3.27-5.19) compared to those on lower doses 1
• In one study, menstrual irregularities occurred in 22% of patients overall, with the effect being dose-related 2
• Another study reported menstrual irregularities in 40.6% of spironolactone users versus 0% in controls (RR 10.89,95% CI 1.54-77.08) 3

Clinical Manifestations

• The most common menstrual side effect is metrorrhagia with shortened cycles (as short as 14-day cycles), which occurred in 56% of women taking 100 mg twice daily 4
• Other menstrual disturbances include irregular bleeding patterns and cycle changes 5
• These effects are related to spironolactone's anti-androgenic and progesterone receptor antagonist properties 1

Management Strategy

Concomitant use of combined oral contraceptives (COCs) or hormonal intrauterine devices can minimize or prevent menstrual irregularities. 1

• Women using combined oral contraception have significantly fewer menstrual adverse effects (odds ratio 0.23,95% CI 0.11-0.50) 6
• COCs are often recommended both to regulate menses and prevent pregnancy, as spironolactone is pregnancy category C 1, 2
• If menstrual irregularities occur without COC use, consider adding hormonal contraception or reducing the spironolactone dose 4
• Starting at 50 mg twice daily (on cycle days 4-21) rather than 100 mg twice daily reduces metrorrhagia risk from 56% to approximately 20% 4

Uterine Fibroids

There is no evidence that spironolactone causes uterine fibroids. The provided evidence extensively documents spironolactone's side effect profile, and uterine fibroids are not mentioned as an adverse effect in any guideline, FDA labeling, or research study 1, 2, 3, 7, 8, 6, 9, 5, 4.

Long-Term Safety Data

• A large retrospective cohort study of 2.3 million women representing 28.8 million person-years showed no association between spironolactone use and uterine cancer 2
• An 8-year follow-up study of 91 women (506 person-years of follow-up, 200 person-years of spironolactone exposure) found no serious illnesses attributable to spironolactone 9
• The FDA label for spironolactone does not list uterine fibroids as an adverse effect 7

Common Pitfalls

• Do not confuse menstrual irregularities with structural uterine pathology: menstrual changes from spironolactone are functional, not due to fibroid development 1, 6
• If a patient on spironolactone develops abnormal uterine bleeding, evaluate for other causes (including pre-existing fibroids) rather than assuming spironolactone caused structural changes 10
• The anti-androgenic effects of spironolactone affect hormonal regulation of the menstrual cycle but do not promote fibroid growth 1