Coadministration has not been studied but is not expected to alter elvitegravir concentrations. No dose adjustment is needed when Stribild (elvitegravir, cobicistat, emtricitabine, tenofovir-DF) is combined with proton pump inhibitors. When omeprazole was administered 2 h prior to elvitegravir/cobicistat, elvitegravir AUC and Cmax increased by 10% and 16% but those of cobicistat decreased by 8% and 10%. Separating omeprazole and elvitegravir/cobicistat by 12 h had no effect (<10% change) on the AUC or Cmax of elvitegravir or cobicistat. Emtricitabine and tenofovir-DF do not interact with dexlansoprazole.