Spironolactone
Aldactone
Half-life
17 hr
Time to Peak
2.6 hr
Steady State
~4 days
Bioavailability
65%
Dose Range
50–200 mg
Frequency
Twice daily
Overview
Spironolactone is a potassium-sparing diuretic used off-label as an anti-androgen in feminizing HRT. It blocks androgen receptors and mildly suppresses testosterone production, typically dosed daily as an oral tablet.
Mechanism of Action
Androgen receptor antagonist. Also inhibits 17-alpha-hydroxylase (mild reduction in testosterone synthesis at high doses). Weak progesterone receptor agonist.
Dosing Information
| Route | Dose Range | Half-life | Tmax | Frequency |
|---|---|---|---|---|
| Oral | 50–200 mg | 17 hr | 2.6 hr | Twice daily |
Common Side Effects
- · Frequent urination (diuretic effect)
- · Dizziness / lightheadedness
- · Hyperkalemia (elevated potassium)
- · Breast tenderness
- · Fatigue
- · Dry skin
- · Irregular menstruation (in those who menstruate)
Monitoring Recommendations
Potassium and renal function (BMP/CMP) at baseline, 1 month, 3 months, then every 6-12 months. Blood pressure monitoring. Testosterone levels to assess efficacy.
Storage & Handling
Room Temperature
Store at 25°C. Excursions permitted 15-30°C.
General
Store in original container. Protect from moisture.
Community Notes
Stay hydrated and watch potassium intake — avoid potassium supplements and excessive high-potassium foods (bananas, coconut water). Many prescribers are moving toward monotherapy with adequate estradiol rather than relying on spironolactone. Frequent urination is expected, especially in the first few weeks.
Used in Regimens
3 regimensOral E2 + Spironolactone
Oral estradiol with spironolactone anti-androgen — the most commonly prescribed transfeminine HRT regimen in North America. Simple, accessible via GP or Planned Parenthood informed consent. Higher VTE risk than transdermal routes due to first-pass hepatic metabolism.
Spironolactone 100–200mg/day. Monitor potassium and BP.
Sublingual E2 + Spironolactone
Sublingual estradiol tablets dissolved under the tongue — bypasses first-pass hepatic metabolism, producing sharp peaks followed by rapid decline. Lower VTE risk than oral. Requires 3–4 daily doses for stable levels. Popular in the US/Canada community.
Spironolactone if T not suppressed by E2 alone.
Transfeminine HRT — Classic Stack
Estradiol valerate injections with spironolactone anti-androgen and progesterone added after 3 months once oestradiol levels are stable. The most common transfeminine HRT regimen globally.
Begin at low dose and titrate up. Monitor potassium and blood pressure.
Data Sources
- FDA Label Aldactone (spironolactone) FDA Prescribing Information
- Guideline Endocrine Society Guidelines for Gender-Affirming Hormone Therapy
Related Tools
Track Spironolactone with Doseline
Reminders, medication level charts, injection site rotation, and protocol tracking — all free, all private.
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