Clinical evaluation of mezlocillin in neonates.

Single-dose pharmacokinetic studies were performed in 64 infants, ranging in age from less than 1 day to 6 days, after intravenous infusion or intramuscular injection of approximately 75 mg/kg of mezlocillin. Mean serum concentrations at one hour were 107 micrograms/ml and 82.5 micrograms/ml for neonates less than or equal to 1 day of age and greater than or equal to 6 days of age, respectively. The serum clearance ranged from 3.0 to 6.4 hours. Based on data from the study, it is recommended that mezlocillin be administered to neonates with gram-negative bacterial infections in a single dose of 75 mg/kg, either as an intravenous infusion over 30 minutes or as an intramuscular injection, every 12 hours during the first week of life. Mezlocillin alone or in conjunction with penicillin was used in treating 165 neonates with suspected sepsis. Gram-negative organisms were recovered from 18 of the 27 neonates from whom pathogens were isolated. Three of these 18 strains, a Klebsiella oxytoca, an Acinetobacter anitratum, and a Haemophilus influenzae, were resistant to mezlocillin in vitro. Twenty-four of the 27 patients who satisfied criteria for evaluation achieved a bacteriological and a clinical cure. Cerebrospinal fluid permeation after multiple doses ranged from 18% to 45% of serum levels. No significant local or systemic side effects were seen. The results indicate that mezlocillin is an effective ureidopenicillin for the treatment of gram-negative bacterial infections.