Valtrex 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 Valtrex (Valacyclovir). The combination is generally fine at 500mg, 1000mg, but a small number of medications can reduce contraceptive efficacy meaningfully and need either a backup method or a switch.
How Valtrex 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 Valacyclovir acts on CYP3A4 determines whether Valtrex affects contraception. Most agents in Antiviral Medications have no clinically meaningful effect on the pill at 500mg, 1000mg.
Practical guidance
According to the prescribing information for Valacyclovir, women on hormonal contraception should review Valtrex 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 Valtrex therapy is the standard mitigation.
Frequently asked questions
Will Valtrex make my pill less effective? ▾
Most Antiviral Medications medications at 500mg, 1000mg do not affect oral contraceptive efficacy. The exceptions are CYP3A4-inducing drugs and a small number of others. The prescribing information for Valacyclovir states whether the interaction is meaningful.
Do I need a backup contraceptive on Valtrex? ▾
Backup contraception is needed only when there is a documented interaction between Valtrex and the contraceptive method. For most users at 500mg, 1000mg, no backup is required. The pharmacist confirms whether Valacyclovir interacts with hormonal contraception.
More on Valtrex
- With alcoholValtrex and alcohol — is it safe to drink?
- With foodShould Valtrex be taken with food?
- Side effectsValtrex side effects: common, rare and warning signs
- Dosage guideValtrex dosage guide: how much to take and when
- OnsetHow fast does Valtrex start working?
- DurationHow long does Valtrex last?
The information on this website is provided for reference and educational purposes only. It does not replace consultation with a qualified healthcare professional.