Ampicillin-associated diarrhea--A prospective study.

A prospective study of 200 consecutive patients receiving ampicillin for various reasons revealed that bowel habits changed in 16% and diarrhea occurred in 4.5%. No case of pseudomembranous colitis was found. The incidence with which bowel habits changed increased with larger total doses of antibiotic. Oral and intravenous routes causedthe same incidence of altered bowel habits. This study provides a proper comparison group to place clindamycin-associated colitis in proper perspective.