Used in the treatment of HIV-1 infection as part of antiretroviral therapy. It works by inhibiting the activity of reverse transcriptase, an enzyme that HIV needs to replicate. Efavirenz is commonly combined with other antiretroviral drugs to reduce viral load, increase CD4 cell count, and slow disease progression. It is taken orally, usually once daily, and is particularly effective in first-line treatment regimens. Due to its long half-life, it maintains effective concentrations in the body over extended periods. However, it may cause central nervous system side effects, so patient monitoring is recommended.