1 Department of Medicine and Neurology, and the Clinical Pharmacology Unit, Children's Hospital Medical Center, and the Department of Pediatrics and Neurology, Harvard Medical School, Boston, Massachusetts
Ampicillin is one of the most frequently used antibiotics in pediatric practice.1 Its clinical efficacy has been widely studied, but its gastrointestinal side effects are poorly documented. In adults with urinary tract infections, 11% taking 1 gm/day of ampicillin orally had bowel movements which were at least twice as frequent as normal.2 Another series in adults receiving ampicillin reported an increase in stools with 16% having
5 and 5% having
5 stools per day. The change in stools increased with total dosage and was equal after oral or intravenous administration.3 In children, ampicillin ranging from 50 to the unusually high dose of 200 mg/kg/day resulted in mild diarrhea (
5 stools per day) in 18% to 30%, moderate diarrhea (5 to 10 stools per day) in 2% to 11%, and severe diarrhea (
10 stools per day) in 1% or less of cases.