Protease inhibitors often cause nausea and diarrhea; nucleoside reverse transcriptase inhibitors are associated with headache, nausea, anemia, and fatigue; and one of the nonnucleoside reverse transcriptase inhibitors, efavirenz, is associated with central nervous system changes. These side effects in turn may affect food intake and nutrition in general. Rifampicin, a drug commonly used to treat tuberculosis, itself a common opportunistic infection, stimulates the cytochrome P450 system of liver enzymes, which in turn significantly speeds up the destruction of protease inhibitors and non-nucleoside reverse transcriptase inhibitors, thereby rendering them less effective