Hormone replacement therapy (estrogen mixture)
Conjugated Estrogens with the birth control pill
Many women of reproductive age take a combined or progestogen-only oral contraceptive while also using a chronic medication such as Conjugated Estrogens (Conjugated Estrogens). The combination is generally fine at 0.3mg, 0.625mg, 1.25mg, but a small number of medications can reduce contraceptive efficacy meaningfully and need either a backup method or a switch.
How Conjugated Estrogens can affect contraceptive efficacy
Combined and progestogen-only contraceptives are metabolised through CYP3A4. Strong CYP3A4 inducers (some antiepileptics, rifampicin, St John's Wort) lower contraceptive plasma levels and reduce efficacy. Whether Conjugated Estrogens acts on CYP3A4 determines whether Conjugated Estrogens affects contraception. Most agents in Hormone replacement therapy (estrogen mixture) have no clinically meaningful effect on the pill at 0.3mg, 0.625mg, 1.25mg.
Practical guidance
According to the prescribing information for Conjugated Estrogens, women on hormonal contraception should review Conjugated Estrogens with the prescribing pharmacist or doctor. Where an interaction is documented, additional barrier contraception or switching to a non-oral method (IUD, implant) for the duration of Conjugated Estrogens therapy is the standard mitigation.
Frequently asked questions
Will Conjugated Estrogens make my pill less effective? ▾
Most Hormone replacement therapy (estrogen mixture) medications at 0.3mg, 0.625mg, 1.25mg do not affect oral contraceptive efficacy. The exceptions are CYP3A4-inducing drugs and a small number of others. The prescribing information for Conjugated Estrogens states whether the interaction is meaningful.
Do I need a backup contraceptive on Conjugated Estrogens? ▾
Backup contraception is needed only when there is a documented interaction between Conjugated Estrogens and the contraceptive method. For most users at 0.3mg, 0.625mg, 1.25mg, no backup is required. The pharmacist confirms whether Conjugated Estrogens interacts with hormonal contraception.
Products containing Conjugated Estrogens
More on Conjugated Estrogens
- With alcoholConjugated Estrogens and alcohol — is it safe to drink?
- With foodShould Conjugated Estrogens be taken with food?
- Side effectsConjugated Estrogens side effects: common, rare and warning signs
- Dosage guideConjugated Estrogens dosage guide: how much to take and when
- OnsetHow fast does Conjugated Estrogens start working?
- DurationHow long does Conjugated Estrogens last?
The information on this website is provided for reference and educational purposes only. It does not replace consultation with a qualified healthcare professional.