Loop diuretic
Furosemide 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 Furosemide (Furosemide) at 20mg, 40mg, 100mg depends on whether the active ingredient Furosemide 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 Loop diuretic class that go through CYP3A4 first-pass metabolism, regular grapefruit consumption can raise plasma levels of Furosemide by a clinically meaningful margin and amplify side effects.
What to do with Furosemide
According to the prescribing information for Furosemide, if grapefruit is flagged as an interaction, the safest practice is to avoid grapefruit entirely or to discuss timing with the prescriber. Furosemide acts on the thick ascending limb of the loop of Henle in the kidney, where it inhibits the Na+/K+/2Cl- co-transporter (NKCC2). A small occasional serving may be tolerable; daily large servings around the time of Furosemide dosing are not recommended at 20mg, 40mg, 100mg.
Frequently asked questions
Can I eat grapefruit while on Furosemide? ▾
For some Loop diuretic medications, grapefruit is best avoided or limited because of CYP3A4 inhibition. Whether Furosemide specifically is affected depends on Furosemide; the prescribing information lists this. When in doubt, ask the pharmacist or check the patient leaflet.
How much grapefruit is too much with Furosemide? ▾
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 Furosemide at 20mg, 40mg, 100mg, individual tolerance varies; the cautious choice is to avoid grapefruit if any interaction is mentioned.
Products containing Furosemide
More on Furosemide
- With alcoholFurosemide and alcohol — is it safe to drink?
- With foodShould Furosemide be taken with food?
- Side effectsFurosemide side effects: common, rare and warning signs
- Dosage guideFurosemide dosage guide: how much to take and when
- OnsetHow fast does Furosemide start working?
- DurationHow long does Furosemide last?
The information on this website is provided for reference and educational purposes only. It does not replace consultation with a qualified healthcare professional.