Theophylline kinetics in a geriatric group

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Abstract
The influence of age, sex and smoking on theophylline [an effective treatment of reversible airway disease] disposition was studied in 38 healthy subjects ranging in age from 26-81 yr. There were 8 young (< 60 yr) and 30 geriatric (> 60 yr) subjects, including 28 men (8 smokers) and 10 women (3 smokers). A crossover experimental design was used. A single dose of theophylline elixir (5 mg/kg lean body wt [LBW]) was given as a reference product to all subjects. One week later a sustained-release (SR) theophylline tablet (8 and 6 mg/kg LBW) was given to the young and the geriatric subjects. Serum theophylline concentrations were determined by HPLC [high-performance liquid chromatography]. Theophylline elimination (t1/2 .beta. [.beta.-phase half-life]) is shorter in the geriatric group (6.93 and 8.14 h); total body theophylline clearance is greater in the geriatric group (44.39 and 32.97 ml/kg per h), and the apparent volume of distribution is greater in the geriatric group (26.29 and 22.97 l). Sex and smoking did not influence any of the parameters studied. In 93% of the geriatric subjects, serum theophylline levels of 8-20 .mu.g/ml were reached at steady state with the SR tablet. Theophylline dose reduction based on an arbitrary age limit is not invariably indicated.