Allegra 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 Allegra (Fexofenadine). The combination is generally fine at 30mg, 60mg, 120mg, 180mg, but a small number of medications can reduce contraceptive efficacy meaningfully and need either a backup method or a switch.
How Allegra 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 Fexofenadine acts on CYP3A4 determines whether Allegra affects contraception. Most agents in Allergy and Antihistamines have no clinically meaningful effect on the pill at 30mg, 60mg, 120mg, 180mg.
Practical guidance
According to the prescribing information for Fexofenadine, women on hormonal contraception should review Allegra 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 Allegra therapy is the standard mitigation.
Frequently asked questions
Will Allegra make my pill less effective? ▾
Most Allergy and Antihistamines medications at 30mg, 60mg, 120mg, 180mg do not affect oral contraceptive efficacy. The exceptions are CYP3A4-inducing drugs and a small number of others. The prescribing information for Fexofenadine states whether the interaction is meaningful.
Do I need a backup contraceptive on Allegra? ▾
Backup contraception is needed only when there is a documented interaction between Allegra and the contraceptive method. For most users at 30mg, 60mg, 120mg, 180mg, no backup is required. The pharmacist confirms whether Fexofenadine interacts with hormonal contraception.
More on Allegra
- With alcoholAllegra and alcohol — is it safe to drink?
- With foodShould Allegra be taken with food?
- Side effectsAllegra side effects: common, rare and warning signs
- Dosage guideAllegra dosage guide: how much to take and when
- OnsetHow fast does Allegra start working?
- DurationHow long does Allegra last?
The information on this website is provided for reference and educational purposes only. It does not replace consultation with a qualified healthcare professional.