Sirolimus–tacrolimus pharmacokinetic interaction

The Sirolimus–tacrolimus pharmacokinetic interaction describes the mutual influence these two immunosuppressants exert on each other's absorption, distribution, metabolism, and excretion. Both drugs are extensively metabolized by the cytochrome P450 3A4 and 3A5 enzymes and are substrates for the P-glycoprotein (ABCB1) efflux pump, leading to competitive inhibition when administered together [8, 13]. This competition often results in altered blood concentrations of one or both drugs, which can increase the risk of dose-dependent toxicities such as nephrotoxicity and neurotoxicity [2, 5]. Furthermore, both drugs bind to the same intracellular receptor, FK506-binding protein 12 (FKBP12), which can lead to pharmacodynamic competition despite their different downstream mechanisms—mTOR inhibition for sirolimus and calcineurin inhibition for tacrolimus [3, 5]. Clinical management requires frequent therapeutic drug monitoring (TDM) and precise dose adjustments to maintain efficacy while minimizing adverse effects in transplant recipients [4, 11]. Genetic factors, particularly polymorphisms in the CYP3A5 and ABCB1 genes, also play a significant role in the magnitude of this interaction [7].

Other names

Tacrolimus-sirolimus interactionFK506-rapamycin interactionSirolimus-tacrolimus drug-drug interactionTacrolimus-sirolimus pharmacokinetic interaction

Competitive inhibition of Cytochrome P450 3A4 and 3A5 (CYP3A4/5) enzymes and P-glycoprotein (ABCB1) efflux transporters, alongside competition for intracellular FK506-binding protein 12 (FKBP12) binding sites.