THE IMPACT OF SYSTEMIC DRUGS ON THE ORAL AND GUT MICROBIOME: A NARRATIVE REVIEW.

Objective: This narrative review examines the impact of systemic drugs, including antibiotics and non-antibiotic medications, on the oral and gut microbiomes, highlighting mechanisms of microbial alteration and clinical implications.

Methodology: A comprehensive literature search was performed using PubMed, Scopus, and Web of Science for studies published from 2014 to 2025. Keywords included "systemic drugs," "oral microbiome," "gut microbiome," and "dysbiosis." Eligible studies involved human or translational animal models addressing drug effects on microbiota. Data were synthesized to identify patterns of microbiome changes and related health outcomes.

Results: Antibiotics induce significant dysbiosis in oral and gut microbiomes, reducing microbial diversity and promoting pathogen overgrowth, which worsens diseases like periodontitis and inflammatory bowel disease. Non-antibiotic drugs such as proton pump inhibitors (PPIs), metformin, psychotropics, and steroids also alter microbiome composition. PPIs reduce gastric acidity, enabling oral bacteria to colonize the gut, increasing infection risk. Metformin fosters beneficial microbial shifts linked to improved metabolism. Psychotropics and steroids modify specific taxa associated with gastrointestinal and metabolic effects. The oral-gut microbiome axis facilitates microbial translocation, contributing to systemic inflammation and disease progression. Additionally, gut microbiota influence drug metabolism and bioavailability, adding complexity to drug-microbiome interactions.

Conclusion: Systemic medications broadly affect oral and gut microbiomes, impacting disease progression and therapeutic outcomes. Recognizing these interactions is vital for optimizing treatment and developing microbiome-friendly strategies. Future research should integrate microbiome insights into personalized medicine to reduce adverse effects and improve efficacy.