 Certain antiretroviral regimens contain drugs with long half-life drugs that stay in the body for a longer period of time after discontinuation than other drugs in the same regimen, such as nevirapine NVP. HIV can easily develop resistance to NVP when NVP is the only drug left in the body similar to monotherapy. Given two other drugs for up to 1 week after discontinue NVP to mimic three-drug regimen while waiting for NVP elimination can help reduce, but not eliminate, the development of resistant virus. 