PROTEASE INHIBITOR - A relatively new class of anti-HIV drugs that prevent the cleavage of protein precursors essential for HIV infection of new cells and viral replication. They have been found to be effective in the treatment of some individuals with advanced HIV infection, particularly when used in combination with other agents (nucleoside analogs). The use of these drugs with other antiretroviral drugs has led to marked clinical improvement and prolonged survival. Examples include ritonavir, saquinavir, nelfinavir, indinavir, and Amprenavir. All can cause gastrointestinal side effects and raise liver enzymes. Use of these drugs has been associated with increased bleeding in hemophilia patients, hyperglycemia, new onset or worsening diabetes, insulin resistance, fat wasting and redistribution, and hyperlipidemia. All are metabolized by cytochrome p450 so drug interactions are common and can be severe. Rifampin should not be used with these medications.