Prophylaxis against ampicillin-associated diarrhea with a lactobacillus preparation.
The efficacy of a lactobacillus preparation (Lactinex) in preventing ampicillin-associated diarrhea in adult inpatients was studied. In a double-blind procedure, 98 patients were assigned randomly to receive one packet of Lactinex (Lactobacillus acidophilus and L bulgaricus) or placebo four times daily for the first five days of ampicillin therapy. Cases of diarrhea were reviewed independently and classified according to etiology. Complete data were obtained for 79 patients--43 received placebo and 36 received Lactinex. Diarrhea occurred in nine (21%) patients receiving placebo and in three (8.3%) patients receiving Lactinex; the difference was not statistically significant (p = 0.21, Fisher's Exact Test). When the patients with diarrhea unrelated to ampicillin were excluded (50%), the incidence of ampicillin-induced diarrhea in the placebo group (14%) was significantly greater (p = 0.03, Fisher's Exact Test) than in the Lactinex group (0%). Prophylactic administration of lactobacillus preparations may be effective in preventing ampicillin-induced diarrhea; however, prophylactic administration appears to be justified, on a cost/benefit basis, only in patients with a history of antibiotic-induced diarrhea.