Plasma disposition of ceftazidime in healthy neonatal foals following intravenous and intramuscular administration

Cephalosporin antimicrobials can be utilized for the treatment of sepsis in neonatal foals, particularly when an aminoglycoside is contraindicated. Some cephalosporins, however, are not utilized because of cost, sporadic availability, or uncertainty about efficacy. The plasma disposition of ceftazidime, a third-generation cephalosporin with a broad spectrum of activity against a wide variety of gram-negative bacteria and minimal renal side effects has not been reported in neonatal foals. In this study, the plasma disposition of single intravenous (IV) and intramuscular (IM) doses of ceftazidime in neonatal foals was determined. Six healthy one to two-day-old foals were given 25 mg/kg of ceftazidime by IV and IM routes in a cross-over design, with a 48-h washout period between doses. Non-compartmental analysis was used to estimate plasma pharmacokinetic parameters. Median t(1/2) was 2 h and median AUC(0-last) was 364 mu g h/ml for both IV and IM administration. Median C-max after IM administration was 101 mu g/ml, with a median T-max of 0.7 h. Relative bioavailability of IM injection was 90%. There were no statistically significant differences between estimated IV and IM pharmacokinetic parameters. Plasma concentrations remained above the human CLSI susceptible breakpoint for Enterobacteriaceae for over 8 h following IV and IM administration.