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In Reply Dr Nozaki and colleagues make the point that to demonstrate interactions between ledipasvir/sofosbuvir and antiretroviral drugs, the plasma blood concentration levels of the drugs should be measured. The package insert for ledipasvir/sofosbuvir states that there are no clinically significant interactions observed or expected with several antiretroviral agents; however, there is a potential for increased tenofovir levels with certain combinations of antiretroviral agents.1 There are no good safety correlations between tenofovir concentrations (either plasma or intracellular levels) and the occurrence of adverse events when used to treat patients with HIV infection.2
Osinusi A, Townsend K, Kottilil S. Drug-Drug Interactions in Patients Co-infected With HCV and HIV—Reply. JAMA. 2015;314(2):186-187. doi:10.1001/jama.2015.6621