Emtricitabine
Emtricitabine is in a class of medications called nucleoside reverse transcriptase inhibitors (NRTIs), according to MedlinePlus, and it works by decreasing the amount of HIV in the blood. Its FDA label states that emtricitabine is indicated in combination with other antiretroviral agents for the treatment of HIV-1 infection. Biktarvy, Tenvir-EM, Viraday and Trustiva each supply it as part of such a combination tablet.
Key points
- Emtricitabine’s boxed warning states that severe acute exacerbations of hepatitis B, including liver decompensation and liver failure, have been reported in patients coinfected with HIV-1 and HBV who discontinue the drug.
- Emtricitabine is phosphorylated by cellular enzymes to emtricitabine 5’-triphosphate, which inhibits HIV-1 reverse transcriptase by competing with the natural substrate deoxycytidine 5’-triphosphate and by being incorporated into viral DNA, terminating the chain.
- The mean absolute bioavailability of emtricitabine capsules is 93%, and after a radiolabelled dose about 86% is recovered in urine and about 14% in faeces, so clearance is principally renal.
- Skin hyperpigmentation, especially on the palms or soles, was very common, at 10% or more, among children taking emtricitabine.
Always part of a combination
Biktarvy combines emtricitabine with bictegravir and tenofovir alafenamide. Tenvir-EM pairs it with tenofovir disoproxil, and Viraday and Trustiva add efavirenz to that same pair.
Hepatitis B exacerbation after stopping treatment
Emtricitabine’s FDA label carries a boxed warning that severe acute exacerbations of hepatitis B, including liver decompensation and liver failure, have been reported in patients coinfected with HIV-1 and HBV who discontinue emtricitabine. Patients coinfected with HIV-1 and HBV who stop taking it should be closely monitored with clinical and laboratory follow-up for several months or more after stopping. If appropriate, the label states that starting anti-hepatitis B therapy may be warranted, especially for patients with advanced liver disease or cirrhosis.