Medicine by the Numbers

A Collaboration of and AFP

Probiotics for Preventing Antibiotic-Associated Diarrhea


Am Fam Physician. 2021 Dec ;104(6):online.


Details for This Review

Study Population: 11,305 adults from 42 randomized controlled trials comparing a probiotic with placebo, alternative probiotic dose, alternative probiotic strain, or no treatment in patients receiving antibiotics

Efficacy End Points: Reduction in antibiotic-associated diarrhea (AAD)

Harm End Points: Adverse events

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Antibiotic-associated diarrhea was prevented in 1 out of 20 patients taking probiotics

No serious adverse events were reported

There was a 5.1% reduction in antibiotic-associated diarrhea



Antibiotic-associated diarrhea was prevented in 1 out of 20 patients taking probiotics

No serious adverse events were reported

There was a 5.1% reduction in antibiotic-associated diarrhea

Narrative: AAD can occur in up to 35% of patients who receive antibiotics and is associated with higher health care costs and increased morbidity and mortality.16 Probiotics consist of live microbes and can improve host-microbial balance and reduce pathogenic bacteria colonization.7 A Cochrane review found that probiotics are protective against Clostridioides difficile–associated diarrhea; however, C. difficile represents only a small proportion of AAD cases.8,9 The meta-analysis summarized in this Medicine by the Numbers evaluated whether probiotics reduce the risk of AAD among adults receiving antibiotics.10

The meta-analysis included 42 randomized controlled trials with 11,305 adults receiving antibiotics of any duration and for any indication. Authors included any strain, dose, or formulation (tablets, powder, yogurt, or fermented milk drink) of probiotic. The included trials evaluated probiotic use compared with placebo, an alternative dose of probiotic (high vs. low dose), an alternative probiotic strain, or no treatment for the prevention of AAD.10 The authors excluded studies that evaluated children and used probiotics for treatment, rather than prevention, of AAD. The probiotic duration was reported in 40 out of 42 studies and ranged from five to 56 days, most commonly for the duration of antibiotic therapy plus seven days.

The primary outcome was the incidence

Author disclosure: No relevant financial affiliations.

Copyright © 2021 MD Aware, LLC ( Used with permission.

This series is coordinated by Christopher W. Bunt, MD, AFP assistant medical editor, and the NNT Group.

A collection of Medicine by the Numbers published in AFP is available at


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1. Francino MP. Antibiotics and the human gut microbiome: dysbioses and accumulation of resistances. Front Microbiol. 2016;6:1543....

2. Young VB, Schmidt TM. Antibiotic-associated diarrhea accompanied by large-scale alterations in the composition of the fecal microbiota. J Clin Microbiol. 2004;42(3):1203–1206.

3. Bishara J, Peled N, Pitlik S, et al. Mortality of patients with antibiotic-associated diarrhoea: the impact of Clostridium difficile. J Hosp Infect. 2008;68(4):308–314.

4. McFarland LV. Antibiotic-associated diarrhea: epidemiology, trends and treatment. Future Microbiol. 2008;3(5):563–578.

5. Kamdeu Fansi AA, Guertin JR, LeLorier J. Savings from the use of a probiotic formula in the prophylaxis of antibiotic-associated diarrhea [published correction appears in J Med Econ. 2012;15(1):205]. J Med Econ. 2012;15(1):53–60.

6. Lenoir-Wijnkoop I, Nuijten MJC, Craig J, et al. Nutrition economic evaluation of a probiotic in the prevention of antibiotic-associated diarrhea. Front Pharmacol. 2014;5:13.

7. Hill C, Guarner F, Reid G, et al. Expert consensus document. The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic. Nat Rev Gastroenterol Hepatol. 2014;11(8):506–514.

8. Goldenberg JZ, Yap C, Lytvyn L, et al. Probiotics for the prevention of Clostridium difficile–associated diarrhea in adults and children. Cochrane Database Syst Rev. 2017;(12):CD006095.

9. Horosheva TV, Vodyanoy V. Sorokulova I. Efficacy of Bacillus probiotics in prevention of antibiotic-associated diarrhoea: a randomized, double-blind, placebo-controlled clinical trial. JMM Case Rep. 2014;1(3):1–6.

10. Goodman C, Keating G, Georgousopoulou E, et al. Probiotics for the prevention of antibiotic-associated diarrhoea: a systematic review and meta-analysis. BMJ Open. 2021;11(8):e043054.



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