Pharmacokinetics of ceftazidime after intravenous and intramuscular administration to domestic cats

The pharmacokinetic properties of ceftazidime, a third generation cephalosporin. were investigated in five cats after single intravenous (IV) and intramuscular (IM) administration at a dose rate of 30 mg/kg. Minimum inhibitory concentrations (MICs) of ceftazidime for some Gram-negative (Escherichia coli, n = 11) and Gram-positive (Staphylococcus spp. n = 10) strains isolated from clinical cases were determined. An efficacy predictor, measured as the time over which the active drug exceeds the bacteria minimum inhibitory concentration (T > MIC), was calculated. Serum ceftazidime disposition was best fitted by a bi-compartmental and a mono-compartmental open model with first-order elimination after IV and IM dosing, respectively. After IV administration, distribution was rapid (t(1/2(d)) 0.04 +/- 0.03 h), with an area under the ceftazidime serum concentration:time curve (AUC((0-infinity))) of 173.14 +/- 48.69 mu g h/mL and a volume of distribution (V-(d(ss))) of 18 +/- 0.04 L/kg. Furthermore, elimination was rapid with a plasma clearance of 0.19 +/- 0.08 L/h kg and a t(1/2) of 0.77 +/- 0.06 h. Peak serum concentration (C-max), T-max,, AUC((0-infinity)) and bioavailability for the IM administration were 89.42 +/- 12.15 mu g/mL 0.48 +/- 0.49 h, 192.68 +/- 65.28 mu g h/mL and 82.47 +/- 14.37%, respectively. Ceftazidime MIC for E coli ranged from 0.0625 to 32 mu g/mL and for Staphylococcus spp. from I to 64 mu g/mL. T > MIC was in the range 35-52% (IV) and 48-72%, (IM) of the recommended dosing interval (8-12 h) for bacteria with a MIC90 <= 4 mu g/mL. (C) 2007 Elsevier Ltd. All rights reserved.