OBJECT DRUGS

Antivirals:

• Amprenavir (Agenerase)
• Atazanavir (Reyataz)
• Darunavir (Prezista)
• Delavirdine (Rescriptor)
• Etravirine (Intelence)
• Fosamprenavir (Lexiva)
• Indinavir (Crixivan)
• Lopinavir (Kaletra)
• Maraviroc (Selzentry)
• Nelfinavir (Viracept)
• Rilpivirine (Edurant)
• Ritonavir (Norvir)
• Saquinavir (Invirase)
• Tipranavir (Aptivus)

PRECIPITANT DRUGS

Enzyme Inducers

• Barbiturates
• Bosentan (Tracleer)
• Carbamazepine (Tegretol, etc.)
• Efavirenz (Sustiva)
• Nevirapine (Viramune, etc.)
• Oxcarbazepine (Trileptal, etc.)
• Phenytoin (Dilantin, etc.)
• Primidone (Mysoline)
• Rifabutin (Mycobutin)
• Rifampin (Rifadin, etc.)
• Rifapentine (Priftin)
• St. John's Wort

Comment:

Enzyme inducers may reduce the serum levels of the protease inhibitors resulting in loss of efficacy or emergence of resistant viral strains. Some combinations result in dramatic reductions in protease inhibitor serum concentrations (e.g., delavirdine + rifampin, and atazanavir + rifampin). The combination of ritonavir and rifabutin may increase the risk of rifabutin uveitis (See Rifabutin + Enzyme Inhibitors).

Class 3: Assess Risk & Take Action if Necessary

• Consider Alternative: Use an alternative to the enzyme inducer if possible. Rifampin is particularly problematic, since it can produce dramatic reductions in the plasma concentrations of protease inhibitors.
• Circumvent/Minimize: Consider increasing the dose of the protease inhibitor.
• Monitor: If it is necessary to use protease inhibitors and enzyme inducers monitor for loss of anti-viral efficacy. Enzyme induction is usually gradual and may take days to weeks for onset and offset, depending on the inducer.