Drugs that May Interact with Protease Inhibitors via CYP3A4 Metabolism -- Table V

The following is a list of medications that may potentially interact with ritonavir therapy via cytochrome P450, specifically CYP3A4 isoenzyme metabolism. Clinical trials measuring the magnitude of these potential interactions have not been conducted. Additionally both saquinavir and indinavir are metabolized via CYP3A4. The extent of these interactions is unknown at this time. Therefore, it may be appropriate to use therapeutic drug concentration monitoring, and/or increased monitoring of therapeutic and adverse effects when concomitantly administering any of the following medications with protease inhibitors, especially for agents with narrow therapeutic margins. Dosage reductions may be required for those medications that are extensively metabolized by CYP3A4.

Please refer to Norvir™ product labeling information for further details regarding other potential drug interactions via CYP2D6, CYP2C9/19, glucuronidation and other pathways.

Drug CategoryDrugs that interact with
Protease Inhibitors via CYP3A4
alfentanil (Alfenta)
fentanyl (Sublimase/Innovar)
Antiarrhythmicsdisopyramide (Rythmodan)
lidocaine (Xylocaine, others)
AnticoagulantR-warfarin (Coumadin)
Anticonvulsantscarbamazepine (Tegretol)
clonazepam (Klonopin)
ethosuximide (Zarontin)
Antihistamineloratadine (Claritin)
Antidepressants, othernefazodone (Serzone)
setraline (Zoloft)
trazodone (Desyrel)
Antiemeticsdronabinol (Marinol)
ondansertron (Zofran)
Antimycobacterialrifampin (Rifadin, others)
Antiparasiticsquinine (various)
Calcium Channel Blockersamlodipine (Norvasc)
diltiazem (Cardizem, Diltiazem)
felodipine (Plendil)
isradipine (DynaCirc)
nicardipine (Cardene)
nifedipine (Adalat, Procardia)
nimodipine (Nimotop)
nisoldipine (Sular)
verapamil (Calan, Isoptin)
Cancer Chemotherapeutic Agentsetoposide (VePesid)
paclitaxel (Taxol)
tamoxifen (Nolvadex, others)
vinblastine (Velban)
vincristine (Oncovin)
Corticosteriodsdexamethasone (Decadron, others)
prednisone (various)
Hypolipidemicslovastatin (Mevacor)
pravastatin (Pravachol)
Immunosuppresantscyclosporine (Sandimmune, Neoral)
tacrolimus (Prograf)

Reference: Norvir™ Prescribing Information (March 1, 1996)

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