Assessments of CYP-Inhibition-Based Drug–Drug Interactions Between Tofacitinib and Lipid-Lowering Agents in Rats Both In Vitro and In Vivo

Tofacitinib is a widely used medication for the treatment of arthritis. It has been reported that some patients experience abnormal cholesterol levels following treatment, leading to recommendations for the coadministration of lipid-lowering drugs such as statins. In this study, we investigated the potential drug–drug interactions between tofacitinib and the statins simvastatin and lovastatin. In the in vitro experiments, rat liver microsomes were employed to evaluate the inhibitory effects of lipid-lowering agents on the metabolism of tofacitinib, with the primary metabolite M8 analyzed using ultra-performance liquid chromatography–tandem mass spectrometry. The results showed that simvastatin and lovastatin significantly inhibited the metabolism of tofacitinib, with IC 50 values of 5.837 and 10.68 μM, respectively. For the in vivo pharmacokinetic studies, Sprague–Dawley rats were pretreated with simvastatin or lovastatin via oral gavage for 7 days before the oral gavage of tofacitinib. This pretreatment led to an increased area under the concentration–time curve of tofacitinib, suggesting that a potential reduction in the first metabolism and/or systemic clearance takes place. These findings demonstrate significant interactions between tofacitinib and certain lipid-lowering agents in the rat model, particularly simvastatin and lovastatin, both in vitro and in vivo.