Absorption of ampicillin and nalidixic acid by infants and children with acute shigellosis

Thirty-seven infants and children with acute shigellosis were treated with orally administered ampicillin or nalidixic acid. Peak plasma levels and dose-response curves suggested two patient populations. Five of 16 patients receiving nalidixic acid had a pronounced delay in absorption, while the others had the anticipated peak levels and plasma half-lifes. All patients had a lower percentage of conjugated drug and of drug present as the hydroxynalidixic acid metabolite on the first day of treatment than during convalescence. Thus, some patients with diarrhea had altered absorption and all had altered metabolism of nalidixic acid during the acute phase of shigellosis. In 10 of 21 ampicillin-treated patients there were depressed plasma levels and prolonged half-lifes. These were statistically likely to be younger, to have more severe diarrhea, and to have lower body weight than those with normal peak plasma levels and plasma clearance rates.