Gut microbiota influence pharmacokinetics variability in aging mice: Effects vary from drug to drug

Pharmacokinetics (PKs) changes in the aging state are relatively common in clinical practice, but their underlying mechanisms remain unclear. This study aims to explore the potential effects of gut microbiota on PK of P450 probe drugs in old and young mice. A cocktail of probe drugs including phenacetin (PHE), midazolam (MID), dextromethorphan tartrate (DEX), and chlorzoxazone was gavage administered to control and pseudo-sterile old and young mice, and the PK parameters were compared. Subsequently, fecal microbiota transplantation (FMT) from young to old mice was performed to assess the impact of FMT on PK of the probe drugs. We observed that gut microbiota significantly affected the systemic exposure of PHE and MID, whereas age-related increase in DEX exposure in the old mice could be reversed by clearance of microbiota. No changes in PK parameters of the probe drugs were observed in old mice with FMT from young mice, suggesting that the alterations in PHE, MID, and DEX metabolism in the old mice could not be explained by unique microbiota from young mice. Our findings provide valuable guidance on how to improve the individualized medication for the elderly population. SIGNIFICANCE STATEMENT: This article offers new insights into the role of gut microbiota in the pharmacokinetic changes with aging, which is conducive to individualized medication for elderly patients and provides new insight for the research and development of drugs for elderly population.