Drug, Food and Supplement — Interactions With Lenvatinib

Both increase the risk of bleeding, which lenvatinib already raises. Paracetamol is generally preferred for mild pain, but the right choice also depends on your kidney function — which lenvatinib can affect — and your full medicines list. Ask your oncology team before taking any regular painkiller rather than assuming paracetamol is always safe in your specific situation.

Yes. Even a small amount of grapefruit or grapefruit juice blocks the enzyme that clears lenvatinib long enough to raise your blood level. This is not a dose effect that scales with how much you eat — it is a chemical block. The simplest and safest approach is to avoid grapefruit and grapefruit juice completely throughout your treatment. Pomelo has a similar effect and is also worth avoiding.

No, not while you are on lenvatinib. St John's Wort speeds up the enzyme that clears lenvatinib, which can reduce the amount in your bloodstream below the level your treatment needs. The EMA and MHRA both specifically flag this combination as one to avoid. If you have been taking it, tell your oncology team before your next dose so they can assess whether your current lenvatinib level has been affected.

Certain epilepsy medicines — including phenytoin, carbamazepine and phenobarbital — and the tuberculosis medicine rifampicin are strong inducers of the enzyme that clears lenvatinib. Your oncologist needs to know about these before you start lenvatinib, because they can significantly reduce how much of the drug reaches your system. Do not stop your epilepsy or TB medicine without specialist guidance — that creates a serious risk of its own, and managing the interaction is a conversation for your oncology and specialist teams together.

It depends on which antifungal. Tablets containing ketoconazole or fluconazole can raise lenvatinib levels by blocking the enzyme that breaks it down. Antifungal creams applied directly to the skin carry much less risk because very little is absorbed into the bloodstream. Tell your oncology team before starting any antifungal tablet so they can advise on the safest option for your situation.

It depends on the antibiotic. Azithromycin and clarithromycin can affect heart rhythm in the same way that lenvatinib does, and combining them raises that risk. Rifampicin, used for tuberculosis, lowers lenvatinib levels significantly and should always be flagged to your oncologist. If you develop an infection and a doctor wants to prescribe an antibiotic, tell them you are on lenvatinib and ask them to check for interactions before writing the prescription.

Most standard multivitamins at normal doses are unlikely to cause a significant interaction. Vitamin E at high doses can increase bleeding risk. Iron supplements can sometimes reduce absorption of oral medicines if taken at the same time — separating them by a few hours is usually enough, but ask your team about timing. The safest approach is to list every supplement at your next appointment so your team can advise on the specific products and doses you are taking, rather than assuming vitamins are a safe category without exception.

Tell the pharmacist dispensing the new medicine that you are on lenvatinib, by name. Pharmacists have access to interaction-checking tools and are often able to advise quickly. If the medicine is not urgent, it is safer to hold it for a day while you reach your oncology team than to take something that may interact. If the medicine is urgent and you cannot wait, go to the centre where you receive your lenvatinib treatment — they can assess it in the context of your full current doses and side-effect profile.