FamotidineRitonavirHistamine H2 AntagonistsLopinavirHIV Protease InhibitorsPyrimidinonesCimetidineRanitidineGastric AcidAnti-Ulcer AgentsSaquinavirGastric Acidity DeterminationMedication AdherenceMedication ErrorsAnti-HIV AgentsIndinavirDrug InteractionsStomach UlcerHIV InfectionsNizatidineTabletsDrug Therapy, CombinationOmeprazoleReceptors, Histamine H2DimapritArea Under CurveCarbamatesLansoprazoleNelfinavir2-PyridinylmethylsulfinylbenzimidazolesCross-Over Studies