Abstract

Probiotics and microbiome-based therapeutics are increasingly used to prevent antibiotic-associated diarrhea (AAD) and support gut microbiota health across children, adults, and elderly populations. Evidence synthesized in this narrative review from randomized controlled trials and meta-analyses (>20,000 participants) suggests that early probiotic administration, particularly Lactobacillus rhamnosus GG, Bifidobacterium species, multistrain formulations, and Saccharomyces boulardii, is associated with a 30–40% relative reduction in AAD incidence across heterogeneous studies, with absolute risk reductions of approximately 5–12% depending on baseline risk, strain, dose, and timing. Probiotics are generally well tolerated, with mild gastrointestinal adverse effects reported in 3–5% of users and rare serious events mainly in immunocompromised individuals. However, heterogeneity in formulations, populations, and limited long-term real-world data underscores the need for further pharmacoepidemiological studies, microbiome surveillance, and evaluation of antimicrobial resistance implications.