H2-receptor antagonist
Famotidine 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 Famotidine (Famotidine) at 10mg, 20mg, 40mg depends on whether the active ingredient Famotidine 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 H2-receptor antagonist class that go through CYP3A4 first-pass metabolism, regular grapefruit consumption can raise plasma levels of Famotidine by a clinically meaningful margin and amplify side effects.
What to do with Famotidine
According to the prescribing information for Famotidine, if grapefruit is flagged as an interaction, the safest practice is to avoid grapefruit entirely or to discuss timing with the prescriber. Famotidine reversibly and competitively blocks histamine H2 receptors on gastric parietal cells, reducing both basal and stimulated gastric acid secretion. A small occasional serving may be tolerable; daily large servings around the time of Famotidine dosing are not recommended at 10mg, 20mg, 40mg.
Frequently asked questions
Can I eat grapefruit while on Famotidine? ▾
For some H2-receptor antagonist medications, grapefruit is best avoided or limited because of CYP3A4 inhibition. Whether Famotidine specifically is affected depends on Famotidine; the prescribing information lists this. When in doubt, ask the pharmacist or check the patient leaflet.
How much grapefruit is too much with Famotidine? ▾
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 Famotidine at 10mg, 20mg, 40mg, individual tolerance varies; the cautious choice is to avoid grapefruit if any interaction is mentioned.
Products containing Famotidine
More on Famotidine
- With alcoholFamotidine and alcohol — is it safe to drink?
- With foodShould Famotidine be taken with food?
- Side effectsFamotidine side effects: common, rare and warning signs
- Dosage guideFamotidine dosage guide: how much to take and when
- OnsetHow fast does Famotidine start working?
- DurationHow long does Famotidine last?
The information on this website is provided for reference and educational purposes only. It does not replace consultation with a qualified healthcare professional.