5-alpha-reductase inhibitor (type II)
Finasteride 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 Finasteride (Finasteride) at 1mg depends on whether the active ingredient Finasteride 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 5-alpha-reductase inhibitor (type II) class that go through CYP3A4 first-pass metabolism, regular grapefruit consumption can raise plasma levels of Finasteride by a clinically meaningful margin and amplify side effects.
What to do with Finasteride
According to the prescribing information for Finasteride, if grapefruit is flagged as an interaction, the safest practice is to avoid grapefruit entirely or to discuss timing with the prescriber. Finasteride binds with high affinity to 5-alpha-reductase type II, blocking the conversion of testosterone into DHT. A small occasional serving may be tolerable; daily large servings around the time of Finasteride dosing are not recommended at 1mg.
Frequently asked questions
Can I eat grapefruit while on Finasteride? ▾
For some 5-alpha-reductase inhibitor (type II) medications, grapefruit is best avoided or limited because of CYP3A4 inhibition. Whether Finasteride specifically is affected depends on Finasteride; the prescribing information lists this. When in doubt, ask the pharmacist or check the patient leaflet.
How much grapefruit is too much with Finasteride? ▾
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 Finasteride at 1mg, individual tolerance varies; the cautious choice is to avoid grapefruit if any interaction is mentioned.
Products containing Finasteride
More on Finasteride
- With alcoholFinasteride and alcohol — is it safe to drink?
- With foodShould Finasteride be taken with food?
- Side effectsFinasteride side effects: common, rare and warning signs
- Dosage guideFinasteride dosage guide: how much to take and when
- OnsetHow fast does Finasteride start working?
- DurationHow long does Finasteride last?
The information on this website is provided for reference and educational purposes only. It does not replace consultation with a qualified healthcare professional.