PHARMACOKINETIC AND CLINICAL STUDIES OF CEFMENOXIME IN NEONATES AND PREMATURE INFANTS

Serum concentrations and urinary recovery rates of cefmenoxime (CMX) were determined in 41 mature and premature infants (with ages 0-24 days) after one shot intravenous injection of 10, 20 (1-hour intravenous drip infusion was also carried out) or 30mg/kg for treatment and prophylaxis of various infections. Because the number of cases included was small, a comparison study was conducted by classifying them into 3 groups; 3 days or younger, 4 to 7 days, and 8 days or older, rather than dividing them into groups of mature and premature infants. Clinical evaluation was conducted in 7 male and 1 female cases 1 to 29 days old, whose diseases comprised 1 case each with septicemia, purulent otitis media and phlegmonous cellulitis, 3 with pneumonia and 2 with urinary tract infection. 1. Changes in serum concentrations and urinary recovery rates (1) Intravenous bolus injection of 10mg/kg: Serum concentrations of the drug in the 3 age groups peaked at 28.9, 29.5 and 29.1μg/ml, respectively, all at 30 minutes after the drug administration, and thereafter gradually declined. The mean level in the 3rd group was the lowest at 1.9μg/ml at 6 hours. Average serum halflives of CMX were shorter in older subjects, 3.0, 1.9 and 1.4 hours, respectively in the 3 groups. Urinary recovery rates were relatively high, 68.9 to 84.9% in the 3 cases examined during the first 6 hours, and 15.4 to 66.2% during the first 2 hours. (2) Intravenous bolus injection of 20mg/kg: Serum concentrations of the drug in the 3 groups peaked at 65.2, 60.5 and 65.8μg/ml, respectively, all at 30 minutes after the drug administration, with no significant differences noted among the groups. The levels gradually declined thereafter in all groups, but remained rather high at 20.1, 6.5 and 9.5μg/ml, respectively, at 6 hours. Average serum half-lives of CMX were 3.5, 1.7 and 1.9 hours, respectively. The inversion of values obtained between the 2nd and 3rd groups appears to be attributable to that all of the 3rd group were premature infants, and the body weight of 2 cases of them were less than 2, 000 g each. Urinary recovery rates ranged widely from 37.0 to 89.4% in the 4 cases examined during the first 6 hours. (3) One-hour intravenous drip infusion of 20mg/kg: Serum concentrations of the drug in the 3 groups peaked at 57.7, 60.2 and 72.4μg/ml, respectively, all at the termination of the drug infusion. The levels remained rather high at 19.1, 7.4 and 8.8μg/ml, respectively, at 6 hours. Average serum half-live