Pharmacokinetics of enprofylline in healthy elderly subjects

The pharmacokinetics of enprofylline, a new potent antiasthmatic, has been studied in 20 healthy, elderly subjects, aged 65 to 81 years, and in 7 young adult controls, aged 23 to 37 years. The dose of 1 mg/kg body weight was given as an i.v. infusion. Plasma levels of enprofylline were followed for about 7 h and urine levels for 24 h. Both groups eliminated the major portion of the dose (about 83%) by renal excretion. As expected the mean creatinine clearance (92.5 ml X min-1 X 1.73 m-2) was moderately decreased in the elderly subjects. The total clearance of enprofylline was 0.16 l X h-1 X kg-1 and the renal clearance was 0.13 l X h-1 X kg-1, which was significantly lower than that in the young controls (0.28 and 0.22 l X h-1 X kg-1) respectively. Thus, the enprofylline clearance had fallen relatively more (about 40%) than the decrease in creatinine clearance (about 20%) with age. The half-life of enprofylline in old age was 2.5 h, which was significantly longer than in the younger adults (1.8 h). It is concluded that the pharmacokinetics of enprofylline was significantly influenced by advanced age, mainly due to reduced renal excretion. This reduction was more pronounced than anticipated from the age-dependent decline in creatinine clearance.