Coadministration has not been studied. Pantoprazole exposure may decrease when administered with by ombitasvir/paritaprevir/ritonavir. Pantoprazole is a substrate of CYP2C19, CYP3A4 and CYP2C9, and is also metabolised by sulfotranseferases. Exposure of omeprazole, a model CYP2C19 substrate, decreased by 50% when administered with ombitasvir/paritaprevir/ritonavir, but exposure of the DAA was not affected. An interaction of similar magnitude is expected with other CYP2C19 substrates. Use higher doses of pantoprazole only if clinically indicated.