Optimal dosage of ampicillin for shigellosis

Thirty infants and children hospitalized for severe shigellosis received oral ampicillin,50 mg. per kilogram per day, for 5 days. Bacteriologic observations and clinical responses were compared with those in patients who had received 100 mg. per kilogram per day of the drug. There were no statistically significant differences between the two dosage groups with respect to bacteriologic cure rates and clinical responses. Super-infection with Candida species occurred less commonly in patients who received the lower dosage. Daily observations on persistence of fever, diarrhea, and positive stool cultures were compared in 103 hospitalized patients who received either of the two dosage schedules of oral ampicillin, intramuscular ampicillin, or placebo. All 3 modes of ampicillin therapy are effective in treatment of shigellosis when the infecting organism is susceptible. Parenteral administration is attended with a significantly more rapid bacteriologic response and lysis of fever and is therefore recommended for the severely ill patient. For others, although there is a tendency to slower response than with 100 mg. per kilogram per day, the lower oral dosage of ampicillin is satisfactory.