Product labels for the nucleotide analogue tenofovir (Viread) in the US are to be changed to include a warning that the safety of the drug for the treatment of HIV and hepatitis B virus coinfection has not been established, the US Food and Drug Administration (FDA) has announced.
Tenofovir has activity against both HIV and hepatitis B virus, and for this reason has been widely prescribed to individuals coinfected with these viruses. The current treatment guidelines of the British HIV Association recommend that tenofovir should be considered as a first-line treatment for HIV/hepatitis B virus infected patients along with the nucleoside analogue 3TC (lamivudine, Epivir). 3TC has been shown to be a safe and effective treatment for HIV and hepatitis B virus coinfection.
However, the new US label for tenofovir includes the warning that “Viread is not indicated for the treatment of chronic HBV (hepatitis B) infection and the safety and efficacy of Viread have not been established in patients coinfected with HIV and HBV. Severe acute exacerbations of hepatitis B have been reported in patients who are coinfected with HIV and HBV and have discontinued Viread.”
Before starting treatment with tenofovir, the FDA is recommending that all HIV-positive individuals should be tested for hepatitis B. The product labeling also recommends that HIV and hepatitis B coinfected patients who have been treated with tenofovir should have their hepatic function closely monitored for several months after discontinuing therapy with the drug, and where appropriate, receive anti-hepatitis B therapy.
Updated information about the pharmacology and the interaction between tenofovir and other antiretrovirals has also been issued by the FDA for inclusion in tenofovir’s packaging. There include a warning that both of the protease inhibitors atazanavir (Reyataz) and Kaletra have been shown to increase concentrations of tenofovir, and that patients taking either of these drugs in combination with tenofovir should be closely monitored for side-effects and that treatment should be discontinued if these occur.
Also included is a caution that tenofovir reduces blood concentrations of atazanavir. For this reason the ritonavir-boosted dose of atazanavir should be prescribed when tenfovir and atazanavir as used in combination.
Mention is also made of the kidney toxicities which tenofovir can cause. Soon after tenofovir was licensed reports of kidney dysfunction associated with its use emerged.
No drug interactions have been seen, the new product label states, between tenofovir and the nucleotide analogue adefovir, which is also used for the treatment of hepatitis B, and the anti-hepatitis C drug ribavirin.
Further information on this website
Tenofovir - overview