Interactions with Other Medications
Overview
HRT medications can interact with other drugs. Some interactions are minor, while others can be dangerous. Always check for interactions when starting a new medication.
Estrogen Interactions
| Medication | Interaction | Severity | Action |
|---|---|---|---|
| Anticonvulsants (phenytoin, carbamazepine) | Reduce estrogen effectiveness | ⚠️ Moderate | May need higher E2 dose |
| Rifampin (antibiotic) | Reduces estrogen levels | ⚠️ Moderate | Monitor E2 levels |
| St. John's Wort | Reduces estrogen effectiveness | ⚠️ Moderate | Avoid if possible |
| Corticosteroids | Estrogen increases corticosteroid levels | ⚠️ Moderate | Monitor for Cushing's symptoms |
| Thyroid medication | Estrogen increases TBG; may need higher thyroid dose | ⚠️ Moderate | Monitor TSH |
| HIV protease inhibitors | Can alter E2 levels | ⚠️ Moderate | Monitor E2 |
Spironolactone Interactions
| Medication | Interaction | Severity | Action |
|---|---|---|---|
| ACE inhibitors (lisinopril, ramipril) | Risk of hyperkalemia (high potassium) | 🔴 Serious | Monitor potassium closely |
| ARBs (losartan, valsartan) | Risk of hyperkalemia | 🔴 Serious | Monitor potassium closely |
| NSAIDs (ibuprofen, naproxen, diclofenac) | Reduced kidney function; hyperkalemia risk | ⚠️ Moderate | Avoid chronic use; monitor potassium |
| Potassium supplements | Hyperkalemia risk | 🔴 Serious | Do NOT take potassium supplements |
| Lithium | Spiro increases lithium levels | ⚠️ Moderate | Monitor lithium levels |
| Digoxin | Spiro increases digoxin levels | ⚠️ Moderate | Monitor digoxin levels |
| Other diuretics | Excessive electrolyte loss | ⚠️ Moderate | Avoid combination |
CPA (Cyproterone Acetate) Interactions
| Medication | Interaction | Severity | Action |
|---|---|---|---|
| Alcohol | CPA increases alcohol sensitivity | ⚠️ Moderate | Limit alcohol intake |
| Antidepressants (SSRIs) | Potential additive effect on depression | ⚠️ Moderate | Monitor mood closely |
| Statins | CPA may increase statin levels | ⚠️ Mild | Monitor if concerned |
| Insulin / diabetes meds | CPA can affect blood sugar | ⚠️ Moderate | Monitor blood glucose |
Bicalutamide Interactions
| Medication | Interaction | Severity |
|---|---|---|
| Warfarin | Bicalutamide may increase warfarin effect | ⚠️ Moderate |
| Statins | Possible increased liver enzyme elevation | ⚠️ Mild |
| Hepatotoxic drugs | Additive liver stress | ⚠️ Moderate |
Progesterone Interactions
| Medication | Interaction | Severity |
|---|---|---|
| CYP3A4 inducers (rifampin, some anticonvulsants) | Reduce progesterone effectiveness | ⚠️ Moderate |
| Benzodiazepines | Additive sedation (especially oral progesterone) | ⚠️ Moderate |
General Precautions
- Always inform your doctor (and pharmacist) that you are on HRT
- Check interactions using a reliable tool (Drugs.com interaction checker)
- Start new medications one at a time so you can identify problems
- Monitor blood work more frequently when adding interacting meds
- Be cautious with alcohol — HRT can change your tolerance
References
Drugs.com. Drug Interaction Checker. https://www.drugs.com/drug_interactions.html
UCSF Transgender Care. Primary care guidelines — medication interactions. https://transcare.ucsf.edu/guidelines