Tissue concentrations of mezlocillin in benign hypertrophy of the prostate following intravenous bolus injection versus infusion.

In 23 patients undergoing transurethral resection or suprapubic operation of benign hypertrophy of the prostate, perioperative antibiotic prophylaxis was started with 5 g of mezlocillin in each patient. In five patients (group I) the antibiotic was given as an intravenous bolus. In five patients (group II) mezlocillin was administered as a bolus of 1 g followed by an intravenous infusion of 4 g over 1 h. In seven patients (group III) and in six patients (group IV) mezlocillin was administered as a bolus of 1 g followed by an intravenous infusion of 4 g over 4 h. In the patients of group I-III a transurethral resection and in the patients of group IV a suprapubic prostatectomy was performed. Serum concentrations of mezlocillin were determined for up to 4 h after the start of the administration. The prostatic tissue concentrations were determined from both prostatic lobes in groups I and II 60 and 90 min and in groups III and IV 4 h after start of administration. In group IV multiple tissue samples of the prostatic adenoma were obtained. The serum concentrations showed considerable interindividual variation, largely because the dose of antibiotic was the same in each patient and not adapted to the body weight. In group I the mean prostatic tissue concentrations at 60 min and 90 min after start of administration were 76 and 31 mg/kg, respectively. In group II the mean prostatic tissue concentrations at 60 min and 90 min were 78 and 24 mg/kg, respectively. In group III the mean tissue concentration at the end of the 4-h infusion was 29 mg/kg. In two patients of this group the concentrations of the two prostatic lobes differed considerably. In group IV measurable tissue concentrations of mezlocillin were found in two patients only. Considerable variations were found within the same prostatic adenoma ranging from undetectable to approximately half of the serum concentration. The diffusion of mezlocillin into the prostatic tissue obviously depends on the size of the prostate. The dependence of concentration within the same adenoma on different histological structures remains to be investigated.