Level 1: Likely reliable evidence

The use of probiotics to prevent diarrhea was evaluated in a randomized trial of 135 hospitalized patients taking antibiotics (BMJ. 2007;335:80; full-text available online free of charge at: www.bmj.com/cgi/content. Accessed January 10, 2008). One-hundred thirty-five patients (mean age 74 years) were randomized to a probiotic yogurt drink (Actimel) 100 g (97 mL) containing Lactobacillus casei, Lactobacillus bulgaricus, and Streptococcus thermophilus vs. sterile milkshake (Yazoo) twice daily starting within 48 hours of initial antibiotics and continuing until one week after completion of antibiotic course. Patients who had received more than two courses of antibiotics in the previous four weeks or who were using high-risk antibiotics (clindamycin, cephalosporins, aminopenicillins) were excluded. One-hundred thirteen patients (84%) were followed for four weeks after finishing the study drink and included in an intention-to-treat analysis; 22 patients (16%) were lost to follow-up, but the rates were similar in both groups.

Comparing probiotic vs. placebo, 12% vs. 34% developed diarrhea (P=.007, NNT 5) and 0 vs. 17% had diarrhea due to Clostridium difficile (P=.001, NNT 6). Only two patients tested positive for C. difficile toxin at baseline, and neither developed diarrhea. Despite a 16% loss to follow-up, the absolute differences were large enough that dropouts would not change the results. Actimel is made by Dannon and marketed as DanActive in the United States.