Non-nucleoside reverse transcriptase inhibitors
NNRTIs are used in combination with other antiretrovirals to treat
HIV infection. The three agents in this class include:
· nevirapine. (See Combining antiretroviral drugs.)
Efavirenz and delavirdine are highly protein-bound after absorp-tion and distribution, and nevirapine is widely distributed through-out the body. All three drugs are metabolized by the cytochrome P-450 liver enzyme system and excreted in urine and stool.
Nevirapine and delavirdine bind to the reverse transcriptase en-zyme, preventing it from exerting its effect, and thus preventing HIV replication. Efavirenz competes for the enzyme through non-competitive inhibition.
NNRTIs are used in combination with other antiretrovirals in HIV treatment; nevirapine is specifically indicated for the patient whose clinical condition and immune status have deteriorated.
NNRTIs may be responsible for many drug interactions.
· Nevirapine may decrease the activity of protease inhibitors and hormonal contraceptives; these drugs shouldn’t be used together.
· Delavirdine may increase levels of benzodiazepines, clar-ithromycin, rifabutin, saquinavir, and warfarin; it may also signifi-cantly increase concentrations of indinavir, requiring a decrease in the indinavir dosage.
· The indinavir dosage will need to be increased when given with efavirenz.
· Nevirapine has been associated with a severe rash that may be life-threatening. If a rash occurs, discontinue the drug. (See Ad-verse reactions to NNRTIs.)