Exploring the Impact of Pharmaceutical Excipient PEG400 on the Pharmacokinetics of Mycophenolic Acid Through In Vitro and In Vivo Experiments

Mycophenolic acid (MPA) is a commonly used immunosuppressant. In the human body, MPA is metabolized into mycophenolic acid 7-O-glucuronide (MPAG) and mycophenolic acid acyl-glucuronide (AcMPAG) mainly through liver glucuronidation, which involves UDP-glucuronosyltransferase (UGTs) and transfer proteins. Research has indicated that the pharmaceutical excipient PEG400 can impact drug processes in the body, potentially affecting the pharmacokinetics of MPA. Due to the narrow therapeutic window of MPA, combination therapy is often used, and PEG400 is widely used in pharmaceutical preparations. Therefore, investigating the pharmacokinetic influence of PEG400 on MPA could offer valuable insights for optimizing MPA's clinical use. In this study, we examined the impact of a single oral dose of PEG400 on the blood levels of MPA in rats through pharmacokinetic analysis. We also investigated the distribution of MPA in various tissues using mass spectrometry imaging. We explored the potential mechanism by which PEG400 affects the metabolism of MPA using hepatic and intestinal microsomes and the Caco-2 cellular transporter model. Our findings reveal that the overall plasma concentrations of MPA were elevated in rats following the co-administration of PEG400, with the AUC_0-t of MPA and its metabolite MPAG increasing by 45.53% and 29.44%, respectively. Mass spectrometry imaging showed increased MPA content in tissues after PEG400 administration, with significant differences in the metabolites observed across different tissues. Microsomal and transport experiments showed that PEG400 accelerated the metabolism of MPA, promoted the uptake of MPA, and inhibited efflux. In conclusion, PEG400 alters the in vivo metabolism of MPA, potentially through the modulation of metabolic enzymes and transport.