Nucleotide analogue reverse transcriptase inhibitors
Nucleotide analogue reverse transcriptase inhibitors are used in combination with other antiretrovirals in the treatment of HIV. The only drug in this class to date is tenofovir, and it works much like the NRTIs.
Tenofovir is absorbed much better after a high-fat meal. It’s then distributed in small amounts into plasma and serum proteins. Me-tabolism isn’t thought to be mediated by cytochrome P-450 liver enzymes, and the drug is excreted by the kidneys.
Tenofovir competes with substrates and is subsequently incorpo-rated into the DNA chain, thus halting HIV replication.
Tenofovir is used in combination with other drugs to treat HIV in-fection.
Tenofovir may be responsible for some drug interactions.
§ Drugs that are eliminated through the kidneys or that decrease kidney function may increase levels of tenofovir when given con-currently.
§ Didanosine levels increase when it’s given with tenofovir; watch for didanosine-based adverse effects.
§ Potentially fatal lactic acidosis and severe hepatomegaly with steatosis have occurred in patients taking tenofovir alone or with other antiretrovirals. The majority of patients were women, and obesity and previous NRTI exposure may be risk factors. Patients with preexisting liver disease should take this drug with caution. Suspend treatment if hepatotoxicity is suspected. (See Adverse re-actions to tenofovir.)