Gut Microbiome-Drug Interactions in Pharmacokinetics, Pharmacodynamics, and Precision Therapeutics

Abstract

Interindividual variability in drug response remains a major challenge in pharmacotherapy and cannot be fully explained by host genetics alone. Research increasingly implicates intestinal microbial activity in differences in drug exposure, treatment effects, and toxicity through its interactions with pharmacokinetic and pharmacodynamic pathways. Drawing on a structured selection of literature, this narrative review examines mechanistic, translational, and clinical findings on drug–microbiome interactions and their implications for precision treatment. The review discusses microbial drug biotransformation, pre-absorptive drug loss, enterohepatic recirculation, metabolic competition, and microbially mediated prodrug activation, with representative examples including digoxin, levodopa, tacrolimus, irinotecan, and mycophenolate. It also evaluates microbiome-derived metabolites and immune signaling pathways that may alter host response states, while distinguishing direct pharmacodynamic modulation from broader physiological effects. In addition, the review examines drug-induced ecological perturbations, microbiome-informed predictive modeling, and microbiome-modulating approaches, including dietary, probiotic, synbiotic, postbiotic, and regulated ecosystem-repair strategies. Current evidence is strongest for selected pharmacokinetic interactions with defined microbial mechanisms and measurable exposure-related outcomes. Whether microbiome-directed interventions will improve routine care remains uncertain, as available clinical evidence is limited and highly context-dependent. Overall, pharmacomicrobiomics provides a useful framework for understanding drug-response variability. Still, clinical translation requires stronger functional biomarkers, controlled intervention studies, external validation, and careful distinction between established, emerging, and hypothesis-generating evidence.