The relationship between theophylline clearance and age in adult life

Fifty three subjects (31 normal volunteers and 22 patients with asthma) between the ages of 20 and 87 years had their theophylline clearance measured. Volume of distribution (V) and terminal elimination half-life (t1/2) were also calculated in the volunteers who received i.v. theophylline. Although patients tended to have higher clearance values than volunteers, in both groups the oldest third had the lowest clearances. For the combined group (corrected for the patient effect) the oldest third (mean age 70 years) had a mean clearance of 0.53 versus 0.72 for the middle third (mean age 47 years) and 0.73 ml/min/kg CBW for the youngest third (mean age 26 years). There was no statistically significant age related change in V/kg CBW but t1/2 did rise with increasing age. Thus, although clearance does not fall with increasing age during younger adult life, there is a fall during late adult life becoming apparent in the seventh, eighth and ninth decades.