Acyclovir and grapefruit: a real interaction?
Grapefruit is famous as the juice that interacts with medications, and the warning is real for a number of drugs. Whether it matters specifically for Acyclovir (Acyclovir) at 200mg, 400mg, 800mg depends on whether the active ingredient Acyclovir is metabolised by CYP3A4 in the gut wall and how much that pathway contributes to first-pass metabolism.
The CYP3A4 mechanism
Grapefruit (and its juice) inhibits CYP3A4 enzymes in the gut wall, increasing the absorbed dose of medications metabolised by that enzyme. For drugs in the Antiviral Medications class that go through CYP3A4 first-pass metabolism, regular grapefruit consumption can raise plasma levels of Acyclovir by a clinically meaningful margin and amplify side effects.
What to do with Acyclovir
According to the prescribing information for Acyclovir, if grapefruit is flagged as an interaction, the safest practice is to avoid grapefruit entirely or to discuss timing with the prescriber. Acyclovir is a guanosine analogue selectively phosphorylated by viral thymidine kinase to its monophosphate form, then by cellular kinases to acyclovir triphosphate. A small occasional serving may be tolerable; daily large servings around the time of Acyclovir dosing are not recommended at 200mg, 400mg, 800mg.
Frequently asked questions
Can I eat grapefruit while on Acyclovir? ▾
For some Antiviral Medications medications, grapefruit is best avoided or limited because of CYP3A4 inhibition. Whether Acyclovir specifically is affected depends on Acyclovir; the prescribing information lists this. When in doubt, ask the pharmacist or check the patient leaflet.
How much grapefruit is too much with Acyclovir? ▾
For drugs where the interaction matters, even modest daily grapefruit intake (one whole grapefruit or one large glass of juice) can shift drug levels noticeably. For Acyclovir at 200mg, 400mg, 800mg, individual tolerance varies; the cautious choice is to avoid grapefruit if any interaction is mentioned.
More on Acyclovir
- With alcoholAcyclovir and alcohol — is it safe to drink?
- With foodShould Acyclovir be taken with food?
- Side effectsAcyclovir side effects: common, rare and warning signs
- Dosage guideAcyclovir dosage guide: how much to take and when
- OnsetHow fast does Acyclovir start working?
- DurationHow long does Acyclovir last?
The information on this website is provided for reference and educational purposes only. It does not replace consultation with a qualified healthcare professional.