Valtrex with antibiotics: interactions and safety
Antibiotic courses are common, short-term and often combined with chronic medications such as Valtrex (Valacyclovir). Most antibiotics do not interfere meaningfully with Valacyclovir at 500mg, 1000mg, but a few classes do, and a small number of combinations are best avoided.
Common antibiotic interactions
Macrolides (clarithromycin, erythromycin) and certain antifungals can inhibit hepatic metabolism (CYP3A4) and raise plasma levels of many medications including some Antiviral Medications agents. Rifampicin has the opposite effect, accelerating metabolism. Most penicillins, cephalosporins, fluoroquinolones and tetracyclines have no clinically meaningful interaction with Valacyclovir at 500mg, 1000mg.
Practical guidance
According to the prescribing information for Valacyclovir, an antibiotic course should be reviewed by the prescriber or pharmacist for known interactions before Valtrex is co-administered. Adjusted 500mg, 1000mg dosing or temporary substitution is sometimes preferred for the duration of the antibiotic course.
Frequently asked questions
Can I take Valtrex during an antibiotic course? ▾
For most common antibiotics, yes. A few classes — notably macrolides and azole antifungals — alter how Valacyclovir is metabolised and may need a temporary 500mg, 1000mg adjustment. The prescribing pharmacist should review any new antibiotic against the existing Valtrex regimen.
Will antibiotics make Valtrex stop working? ▾
Most antibiotics do not affect Valtrex efficacy. Rifampicin and a few others can lower Valacyclovir levels and reduce effect; in those cases the prescriber may adjust the dose during and shortly after the antibiotic course.
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.