Recent studies have shown that coadministration of certain protease inhibitors (PIs) with gastric acid-reducing agents results in decreased plasma concentrations of the PI. To assess the effect of acid-reducing agents on lopinavir/ritonavir, data from two clinical trials (n = 38 and 190) were pooled. Both trials randomized antiretroviral-naïve, HIV-infected patients to receive lopinavir/ritonavir 400/100 mg twice-daily or 800/200 mg once-daily in combination with stavudine and lamivudine, or tenofovir and emtricitabine. Concurrent administration of gastric acid-reducing agents including antacids of various brand names, proton pump inhibitors (omeprazole, esomeprazole, lansoprazole, pantoprazole, and rabeprazole), and H2-receptor antagonists (ranitidine, famotidine, cimetidine, and nizatidine) was reported in both trials. Lopinavir and ritonavir pharmacokinetic parameters were evaluated. Thirty subjects were considered users of acid-reducing agents at the times of pharmacokinetic evaluation. HIV-infected patients who received gastric acid-reducing agents during administration of lopinavir/ritonavir-based treatment regimens did not appear to have a reduction in lopinavir or ritonavir exposures.