Pharmacokinetic and Clinical Studies on Aztreonam in Neonates and Premature Infants

Aztreonam (AZT) was studied for its pharmacokinetics, clinical effect and effect on intestinal bacterial flora in neonates, and the results obtained are summarized as follows: 1. Serum concentrations of AZT upon intravenous administration of 20 mg/kg were 38.6 μg/ml in 30 minutes, 30.6 μg/ml in 1 hour and 13.6 μg/ml in 6 hours. The T 1/2 was 3.73 hours. Ampicillin (ABPC) 25 mg/kg was concurrently used with AZT in 2 cases and serum concentrations of AZT in these 2 cases were 40.3 and 36.9 μg/ml in 30 minutes, 35.7 and 32.6 μg/ml in 1 hour, and 13.1 and 10.2 μg/ml in 6 hours, respectively. T 1/2's were 3.32 and 2.91 hours, respectively, and no interaction between the 2 drugs was observed. 2. AZT was administered to 21 neonates between 0 and 83 days of age and ABPC was concurrently administered to 18 of the cases. Clinical evaluation was made in 14 cases, where AZT was remarkably effective in 7 cases, effective in 6 cases and not effective in 1 case. Of the 21 cases,1 case of diarrhea, 1 case each of eosinophilia, an increase in platelets, an increase in platelets and an elevation of GOT and a decrease in platelets were recorded. 3. With respect to effects of AZT on intestinal bacterial flora, fecal concentrations of AZT upon its single administration to 2 cases were low suggesting, there was little effect on the intestinal flora. Some effect on anaerobes, however, was recognized in 4 cases in which ABPC was concurrently used.