Single-dose pharmacokinetics of dicloxacillin in healthy subjects of young and old age.

Dicloxacillin was administered as 2 g single intravenous doses to healthy young and old subjects of both sexes aged 19-32 years and 65-76 years, respectively, and the pharmacokinetics were studied. Peak serum concentrations were higher in young than in elderly subjects and in each age group in females than in males. The elimination rate was similar in all groups and the only striking pharmacokinetic differences observed were that the urinary recovery of active dicloxacillin was higher in young subjects and that the non-renal clearance was higher in elderly volunteers. The findings were interpreted to be due to a systemic metabolism of dicloxacillin, compensating for a reduced renal elimination in the elderly subjects. In all subjects dicloxacillin was well tolerated. No increases of serum creatinine were observed.