Drug interactions

Fosamprenavir (Telzir) is metabolised by the cytochrome P450 enzymes in the liver, particularly the CYP3A4 enzyme. Consequently, its levels are affected by other drugs that use the same pathway.

Many other drugs using the CYP3A4 enzyme should not be given with fosamprenavir, as their levels may be altered. These include:

  • Alfuzosin
  • Astemizole
  • Cisapride
  • Colchicine in people with renal or hepatic impairment
  • Diazepam
  • Ergotamine tartrate (Cafergot / Migril)
  • Flecainide acetate (Tambocor)
  • Flurazepam (Dalmane)
  • Fluticasone propionate (Flixotide): taking this with fosamprenavir can cause symptoms of Cushing’s syndrome and suppression of the adrenal glands, including weight gain, weakening of the skin, sweating, facial hair growth and psychological disturbances.
  • Halofantrine
  • Hypericin (St John’s wort)
  • Lovastatin
  • Lumefantrine
  • Midazolam (Hyponovel)
  • Pimozide (Orap)
  • Propafenone (Arythmol)
  • Rifampicin (Rifadin / Rimactane)
  • Simvastatin (Zocor)
  • Terfenadine
  • Triazolam.

Caution is advised when taking any protease inhibitor with the impotence drugs sildenafil (Viagra), tadalafil (Cialis) or vardenafil (Levitra). When taken with fosamprenavir, levels of these drugs may increase making side-effects more likely. Commencing the drugs at a reduced dose is advised. Sildenafil is contraindicated if used for treatment of pulmonary arterial hypertension.

Levels of the lipid-lowering drug atorvastatin (Lipitor) are increased by ritonavir-boosted fosamprenavir. A low dose of atorvastatin is recommended.

Other drugs that should be used cautiously or whose levels should be checked in people taking fosamprenavir include:

  • Amiodarone hydrochloride (Cordarone X)
  • Amitriptyline hydrochloride
  • Amlodipine (Istin)
  • Bepidril
  • Carbamazepine (Tegretol / Carbagen SR / Tegretol Retard)
  • Ciclosporin (Neoral / Sandimmun)
  • Dexamethasone hydrochloride
  • Diltiazem (Tildiem / Adizem-SR / Adizem-XL / Angitil SR / Angitil XL / Calcicard CR / Dilcardia SR / Dilzem SR / Dilzem XL / Slozem / Tildiem LA / Tildiem Retard / Viazem XL / Zemtard)
  • Felodipine (Plendil)
  • Imipramine hydrochloride
  • Isradipine (Prescal)
  • Itraconazole (Sporanox)
  • Ketoconazole (Nizoral)
  • Lidocaine hydrochloride (Minijet Lignocaine / Xylocaine)
  • 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)
  • Nimodipine (Nimotop)
  • Nisoldipine (Syscor MR)
  • Phenobarbital
  • Phenytoin (Epanutin)
  • Quinidine (Kindin Dureles)
  • Rapamycin
  • Tacrolimus (Prograf / Protopic)
  • Verapamil hydrochloride (Cordilox / Securon / Half Securon SR / Securon SR / Univer / Verapress MR / Vertab SR 240)
  • Warfarin sodium.
Community Consensus Statement on Access to HIV Treatment and its Use for Prevention

Together, we can make it happen

We can end HIV soon if people have equal access to HIV drugs as treatment and as PrEP, and have free choice over whether to take them.

Launched today, the Community Consensus Statement is a basic set of principles aimed at making sure that happens.

The Community Consensus Statement is a joint initiative of AVAC, EATG, MSMGF, GNP+, HIV i-Base, the International HIV/AIDS Alliance, ITPC and NAM/aidsmap
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This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.

NAM’s information is intended to support, rather than replace, consultation with a healthcare professional. Talk to your doctor or another member of your healthcare team for advice tailored to your situation.