[Pharmacokinetic and clinical evaluation of aztreonam in neonates and premature infants].

In order to study serum concentration and urinary concentration (urinary recovery rate) of aztreonam (AZT), AZT was administered via intravenous bolus injection at dose levels of 10 mg/kg, 20 mg/kg and 50 mg/kg to 7 cases of 4 to 26 days old mature or premature infants nearing cure-stage of various bacterial infections upon the treatment with AZT. Clinical evaluation was made in 19 cases with therapy with AZT alone and 13 cases with combination therapy with AZT + ampicillin (ABPC), with a total of 32 cases. The former group included 10 males and 9 females of 0 to 43 days of age and the latter group included 7 males and 6 females of 6 to 41 days of age. All the cases treated with AZT alone including 5 cases for prophylaxis were evaluable. In the 13 combination therapy cases, however, the effect of AZT was evaluable only in 3 cases excluding the cases in which ABPC-susceptible bacteria were the culprits. 1. Changes in serum concentrations and urinary recovery of AZT. Pharmacokinetics of AZT in serum was examined in 5 matured infants at dose levels of 10 mg/kg in 2 cases and 20 mg/kg in 3 cases. Highest levels were observed with the first sampling at 30 minutes after administration in all the cases with values of 29.1 micrograms/ml with 10 mg/kg dose, and 37.8 micrograms/ml and 55.5 micrograms/ml with 20 mg/kg dose in in cases with ages between 4 and 7 days and 1 case with age above 8 days, respectively. Half-life (T 1/2) values were 3.42, 3.05 and 1.58 hours, respectively for the above three groups of patients. As is described here, the T 1/2 value in the infant with age above 8 days was considerably shorter than the T 1/2 values in infants of younger day-ages. Urinary recovery rates of administered AZT were between 10.4 and 52.6%, showing a large individual diversity. In addition to the above cases, one premature infant was administered with AZT (the dose level: 50 mg/kg) and examined for pharmacokinetic parameters at day-ages of 11 days and 19 days. Serum levels of AZT examined were the highest at 30 minutes after dosage (the first sampling) and were 106.8 micrograms/ml at 11 days of age, and 90.4 micrograms/ml at 19 days of age. Serum levels decreased to 16.2 and 9.6 micrograms/ml, respectively, in 8 hours after dosage, at ages of 11 and 19 days. T 1/2 values were 2.62 and 2.35 hours, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)