[Studies of aztreonam in neonates]

Absorption and excretion of aztreonam (AZT) in neonates were studied and its clinical evaluation in 10 cases of neonates was performed using 1 hour intravenous drip infusion. 1. Serum concentrations of AZT in 7 neonates younger than 11 days of age were lower than those in infants. 2. Serum concentrations of AZT in 5 neonates given 20 mg/kg reached their peaks at the end of intravenous drip infusion with an average value of 45.8 +/- 10.41 micrograms/ml, and T 1/2 was 2.77 +/- 0.32 hours on the average. 3. Serum concentrations of AZT in 2 neonates given AZT 25 mg/kg reached their peaks at the end of intravenous drip infusion at 31.1 and 33.4 micrograms/ml with little difference from the 20 mg/kg group. Half-lives of serum AZT in the 2 cases were 1.87 hours and 3.23 hours, respectively. 4. Urinary excretion rates of AZT in 7 neonates younger than 11 days of age in the first 6 to 8 hours after the administration were 18.8 to 50.0%, or 31.7% on the average, which was lower than the average excretion rate found with infants. 5. All the cases given AZT showed clinical results rated better than "effective". Effect of AZT was excellent on 3 UTI cases caused by Escherichia coli and Klebsiella pneumoniae, but bacterial replacement (superinfection) of Enterococcus faecalis was observed when AZT was administered. 6. Transient elevations of GOT and GPT were seen in 2 cases when AZT administration was continued at length. Clinical side effect was not observed. 7. The most appropriate dosage and administration scheme of AZT against Gram-negative infections in neonates seems to be 40-60 mg/kg/day, b.i.d. or t.i.d.