Antiviral hepatitis and antiretroviral drug interactions

More and more HIV-infected patients are treated for viral hepatitis, increasing interactions. HEPATITIS C: The concomitant use of didanosine and ribavirin increases the risk of mitochondrial toxicity, responsible for pancreatitis and/or lactic acidosis. Lactic acidosis is characterized by a high mortality rate. Thus, didanosine, but also stavudine, should not be co-administered with ribavirin. Cases of hepatic decompensation have been reported in cirrhotics concomitantly receiving ribavirin and didanosine. Thus, this co-admininistration should be contraindicated in patients with advanced liver fibrosis. Anemia is a frequent side effect of ribavirin. In patients with zidovudine-related anemia, this drug should be discontinued before prescribing ribavirin. Erythropoietin may help to improve the haemoglobin level. HEPATITIS B: Adefovir significantly decreases the plasma levels of saquinavir. Pancreatitis may occur with the co-administration of didanosine and tenofovir. Thus this co-administration should be avoided. Atazanavir concentrations are decreased when tenofovir is co-administered. Thus, atazanavir should be boosted with ritonavir, when combined with tenofovir. Atazanavir increases the concentrations of tenofovir, with the potential risk of increasing the adverse events of tenofovir, including renal disorders. Tenofovir area under the curve is increased if lopinavir-ritonavir are co-administered. The main interactions, with a fatal risk, are observed with didanosine, when co-administered with ribavirin (hepatitis C) or with tenofovir (hepatitis B). Anemia is frequent, but usually moderate, when zidovudine is co-administered with ribavirin. Other interactions are usually easy to manage.