1979 Volume 28 Issue 8 Pages 647-653
The pharmacokinetics of theophylline were studied using high-presser liquid-chromatography on 6 normal volunteers and 33 asthmatic patients to determine optimal dosage regimen. Regarding apparent volume of distribution, values of 0.44±0.03l/kg (mean±SE) and 0.40±0.01lkg (mean±SE) were obtained in the volunteers and patients respectively. Half-life of the drug was 9.47±0.86 hr (mean±SE) which was longer than that previously reported by Schack and Waxler's method. Large half-life variability (10.03±0.85 hr mean±SE : range : 4.00-23.41 hr) was observed in the patients and a marked prolongation of the half-life was noted in those over 60 years of age. The effect of aging was not elucidated since most of the patients above 60 years had congestive heart disease. Plasma level of theophylline is obviously dependent on the pharmacokinetic factors. Therefore, individualization of dosage calculation and plasma level monitoring are essential for rational use of theophylline.
