Drug-drug interactions (DDI) between tacrolimus (TAC) and proton pump inhibitors (PPIs) were summarized to assess magnitude of the DDI in terms of the Cytochrome P450 (CYP) responsible for TAC and PPIs metabolism. The combined use of TAC and PPIs, omeprazole and lansoprazole, provides a DDI, that increase blood levels of TAC. Omeprazole and lansoprazole inhibit the TAC metabolism on CYP3A4, a common metabolic enzyme for both PPIs and TAC, as the estimated mechanism for DDI. It has been reported that genetic polymorphisms of CYP2C19, an another metabolic enzyme for PPIs, were associated with this DDI, where poor metabolic ability for PPIs enhanced the magnitude. On the other hand, co-administration of rabeprazole, an alternative PPIs, provides little effect on this DDI because the main metabolic pathway is non-enzymatic degradation. The information is limited whether or not vonoprazan, a novel PPIs and substrate for CYP3A4, produces DDI with TAC as well as conventional PPIs. We present a case of renal transplant recipient whose blood TAC was increased after introduction of vonoprazan, suggesting a potential DDI with TAC.
