[Pharmacokinetics and dosage of mezlocillin administered by intravenous infusion]

Mezlocillin was administered to seven healthy adults by i. v. infusion at two different speeds. They received 1.6 g mezlocillin in five minutes with the initial loading infusion and 1.3 g mezlocillin in one hour with the following infusion. Our aim was to achieve a 100 mg/l steady state serum concentration. The mezlocillin concentrations in the serum averaged 118.7 (+/- 31.2) mg/l at the end of this infusion. Four hours later they were 2.79 (+/- 1.41) mg/l and after six hours 0.96 (+/- 0.93) mg/l. The urinary excretion during the six hours averaged 60.5% of the applied dose of 2.9 g mezlocillin. The pharmacokinetic parameters of mezlocillin were calculated automatically using a two-compartment model. The average values were the following: biological half-life (beta) 72.7 (+/- 26) minutes; total plasma clearance 2.447 (+/- 0.586) ml/s; distribution volume (Vd area) 15.30 (+/- 6.12) l, i. e. 0.21 l/kg. Deviations from the mezlocillin serum concentrations desired (100 mg/l) are explained by interindividual differences in the pharmacokinetic behaviour and by the use of a two-compartment model.