HIV and drug allergy.

Drug-related rashes have been estimated to be 100 times more common in HIV-positive patients than in the general population. The reasons for this are not clear, but are likely to be multifactorial, and include changes in drug metabolism, oxidative stress, cytokine profiles and immune hyperactivation. HIV itself may also serve as a danger signal, leading to the development of an immune response rather than tolerance. Drugs that are implicated in causing hypersensitivity have changed since the advent of highly active antiretroviral therapy. This is largely as a result of a decrease in the use of antimicrobials such as co-trimoxazole, and the introduction of new drugs of different classes, including abacavir, non-nucleoside reverse transcriptase inhibitors such as nevirapine, and protease inhibitors such as amprenavir. Laboratory evidence supporting a role of the immune system in the mechanism of co-trimoxazole hypersensitivity is available. However, this is not the case for the newer antiretrovirals; hypersensitivity to these agents is presumed to be immune-mediated based only on the symptomatology. It is essential that research be carried out into the mechanisms of hypersensitivity reactions associated with these important new classes of drugs so that their benefit-risk ratio can be improved, and lessons learned for future drug development.