Darunavir (Prezista) is broken down through the cytochrome 3A4 system in the liver. The manufacturer expects this to lead to significant interactions with other drugs that are metabolised in this manner. Based on this information, patients taking darunavir should not take the following drugs:

• Astemizole.
• Carbamazepine (Tegretol).
• Cisapride.
• Dihydroergotamine.
• Ergonovine.
• Ergotamine tartrate (Cafergot / Migril).
• Hypericin (St John’s wort).
• Lovastatin.
• Methylergonovine.
• Midazolam (Hypnovel).
• Phenobarbital.
• Phenytoin (Epanutin).
• Pimozide (Orap).
• Rifampicin (Rifadin / Rimactane).
• Simvastatin (Zocor).
• Terfenadine.
• Triazolam.

The following drugs may require a dose adjustment in patients taking darunavir, or may require darunavir’s dose to be altered. Until more data are available they should be used with darunavir cautiously:

• Atorvastatin (Lipitor).
• Bepidril.
• Ciclosporin (Neoral / Sandimmun).
• Dexamethasone.
• Efavirenz (Sustiva).
• Felodipine (Plendil).
• Fluticasone propionate (Flixotide).
• Indinavir (Crixivan).
• Itraconazole (Sporanox).
• Ketoconazole (Nizoral).
• Lidocaine.
• Methadone hydrochloride (Methadose).
• Nicardipine hydrochloride (Cardene / Cardene SR).
• Nifedipine (Adalat / Adalat LA / Adalat Retard / Adipine MR / Adipine XL / Cardilate MR / Coracten SR / Coracten XL / Fortipine LA 40 / Hypolar Retard 20 / Nifedipress MR / Nifopress Retard / Slofedipine / Slofedipine XL / Tensipine MR).
• Paroxetine (Seroxat).
• Pravastatin sodium (Lipostat).
• Rifabutin (Mycobutin).
• Ritonavir-boosted lopinavir (Kaletra).
• Quinidine sulphate.
• Sertraline (Lustral).
• Sildenafil (Viagra): a reduced dose is recommended.
• Sirolimus (Rapamune).
• Tacrolimus (Prograf).
• Tadalafil (Cialis): a reduced dose is recommended.
• Trazodone hydrochloride (Molipaxin).
• Vardenafil (Levitra): a reduced dose is recommended.
• Voriconazole (Vfend).
• Warfarin sodium.

Women using ethinylestradiol or norethidrone as hormonal contraception may experience reduced levels of the contraceptive if they take darunavir. Additional or alternative methods of contraception are recommended.

Tibotec is planning to carry out further studies into interactions between darunavir and other drugs.