[Pharmacokinetic and clinical evaluations of aztreonam monotherapy and aztreonam and ampicillin combination therapy in neonates and premature infants].

One-shot intravenous injection of aztreonam (AZT), a monobactam-class beta-lactam antibiotic, 20 mg/kg was administered to 4 neonates and 2 premature infants, a total of 6 cases, and plasma and urinary concentrations and urinary recovery rates were determined. Also, one-shot intravenous injection averaging 70.9 mg/kg/day of AZT alone was given to 0- to 43-day neonates and premature infants in b.i.d. to q.i.d. for an average of 8 days for the treatment (6 cases) and prophylaxis (11 cases) of infections. Furthermore, a combination therapy of AZT and ampicillin (ABPC) was applied to 0- to 79-day neonates and premature infants for the treatment (28 cases) and prophylaxis (18 cases) of infections. Average daily dosage of AZT 46.6 mg/kg was given by one-shot intravenous injection or by drip infusion in b.i.d. or t.i.d. for an average of 8 days. Average daily dosage of ABPC 78.6 mg/kg was given in the same daily frequency, route and average duration as AZT. Thus, clinical effects, prophylactic effects against infection, bacteriological effects as well as side effects and clinical laboratory test values were studied with the following results. 1. When AZT 20 mg/kg was administered to 1 case each of 6- and 7-day neonates by one-shot intravenous injection, the plasma concentrations were the highest at 5 minutes after the administration in both cases. Specifically, they were 62.9 and 72.7 micrograms/ml with AUCs of 216.6 and 231.6 micrograms.hr/ml and half-lives of 2.80 and 2.97 hours, respectively. When AZT 20 mg/kg was administered to 5- and 6-day premature infants by one-shot intravenous injection, the plasma concentrations were the highest at 15 minutes after administration in the former and 5 minutes in the latter, at values of 59.8 and 67.7 micrograms/ml, respectively. AUCs were 356.6 and 363.2 micrograms.hr/ml, respectively, and larger than AUCs of the above-mentioned neonates. Half-lives were 5.74 and 4.87 hours, respectively and longer than those of the above-mentioned neonates. When AZT 20 mg/kg was administered to 8- and 13-day neonates by one-shot intravenous injection, the plasma concentrations were the highest at 30 minutes after administration in the former and 5 minutes in the latter, at values of 43.4 and 76.9 micrograms/ml, respectively. AUCs were 202.9 and 189.8 micrograms.hr/ml, and 76.9 micrograms/ml, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)