[A study on cefmetazole in the neonatal period (author's transl)].

The authors studied the antibacterial activity, absorption and excretion, and clinical use of cefmetazole in neonatal period, and obtained the following results. 1. The minimal inhibitory concentrations (MICs) of cefmetazole (CMZ) were measured, to compare with those of cefazolin (CEZ), for clinical isolates of S. aureus (31 strains), E. coli (29 strains) and K. pneumoniae (30 strains). On a cumulative percentage basis, 77% of S. aureus, 76% of E. coli and 90% of K. pneumoniae were inhibited by less than or equal to 3.13 microgram/ml of CMZ with a higher inoculum size. When compared with CEZ, MICs of CMZ were found to be superior or equal against E. coli, K. pneumoniae and some of S. aureus, but to be inferior against most of S. aureus. Most of strains which were resistant to CEZ were most sensitive to CMZ. These results suggest that CMZ is highly active against Gram-negative bacteria and is stable to beta-lactamase. 2. The serum concentration was measured in 7 neonates (5 approximately equal to 25 day-old) and 5 infants (1 approximately 3 month-old) after a single intravenous administration of 20 approximately 25 mg/kg of CMZ. The mean concentration in neonates was 68.3 microgram/ml at 1/2 hour postinjection, 57.0 microgram/ml at 1 hour, 35.4 microgram/ml at 2 hours, 18.1 microgram/ml at 2 hours, 18.1 microgram/ml at 4 hours and 9.5 microgram/ml at 6 hours. The mean half-life was 2.04 hours. The peak concentration of each neonate seemed to be related more to individual variation than to the days after birth. The mean concentration in infants was 60.7 microgram/ml at 1/2 hour, 42.8 microgram/ml at 1 hour, 22.2 microgram ml at 2 hours, 9.2 microgram/ml at 4 hours and 3.2 microgram/ml at 6 hours. The mean half-life was 1.31 hours. There was little difference in the mean peak concentration between neonates and infants, but the mean concentration after that were higher in neonates than infants. It was apparent that the half-life tends to be shortened in proportion to advanced age in days and months. 3. CMZ was administered clinically in 3 cases of acute bronchopneumonia. Its clinical effect was excellent or good in all of the cases. No adverse reaction or abnormal laboratory values were found.