Coadministration of glecaprevir/pibrentasvir and omeprazole (20 mg once daily) decreased glecaprevir Cmax and AUC by 22% and 29%. Coadministration of glecaprevir/pibrentasvir and omeprazole (40 mg once daily taken 1 hour before breakfast) decreased glecaprevir Cmax and AUC by 64% and 51%. When omeprazole was administered in the evening without food, glecaprevir Cmax and AUC decreased by 46% and 49%. Despite the decrease in glecaprevir exposure with omeprazole there is no change in pibrentasvir exposure and, therefore, virological suppression is expected to be maintained. The European SPC for glecaprevir/pibrentasvir indicates that no dose adjustment is required and the US Prescribing Information indicates no clinically significant interaction and no dose adjustment required. However, it is important to note that currently there are no data with doses of omeprazole greater than 40 mg once daily.