sofosbuvir + efavirenz + emtricitabine + tenofovir disoproxil fumarate

This is a **combination drug** consisting of four active antiretroviral ingredients: **sofosbuvir** (a nucleotide analog NS5B polymerase inhibitor most commonly used against hepatitis C virus), **efavirenz** (a non-nucleoside reverse transcriptase inhibitor, NNRTI), **emtricitabine** (a cytidine analogue nucleoside reverse transcriptase inhibitor, NRTI), and **tenofovir disoproxil fumarate** (an acyclic nucleotide analogue NRTI). Efavirenz, emtricitabine, and tenofovir disoproxil fumarate together form a widely used anti-HIV fixed-dose combination, often branded as **Atripla**, and are approved for the treatment of HIV-1 infection[1][2][4][5]. Adding sofosbuvir, which is not part of any established fixed-dose combination for HIV treatment, is notable for its use against hepatitis C virus (HCV). The combination would theoretically be used to treat patients co-infected with HIV and HCV, but this specific four-drug combination is not a recognized or branded product and is not approved as a fixed-dose formulation by any regulatory agency. **Mechanism of Action:** - Sofosbuvir inhibits HCV RNA replication by acting on the NS5B polymerase. - Efavirenz non-competitively inhibits HIV-1 reverse transcriptase. - Emtricitabine and tenofovir disoproxil fumarate inhibit HIV-1 reverse transcriptase by competing with natural nucleotides and causing chain termination. The result is blockade of both HIV replication and (potentially) HCV replication in co-infected patients.