Regardless of the mechanism, since t½ increases during adolescence, theophylline dose and interval need to be adjusted carefully during the teenage years. During puberty, changes in body composition and liver function occur which may influence drug distribution and metabolism, thereby contributing to the increase in drug t½. Puberty, (defined by age or Tanner Stage) accounts for 20% of the variability, whereas genetically determined rates of metabolism and environment probably account for much of the remaining inter-individual variation in t½. Mean t½ of females (6.54 hr.) was longer than males (5.59). T½ elim calculated from serum levels ranged from 2.8 – 8.5 hr. Duplicate samples were analyzed by fluorescent polarization technique (coef. only a limited quantity of radionuclides with a longer half-life.2. Following a single dose of short-acting theophylline (4-6 mg/kg) PO or IV, timed serum samples (ndniman 3, maximum 22 samples per patient) were obtained between 6–24 hrs. Our research and development laboratories the sp Hard Rock Laboratory (HRL). After at least 2 weeks of long-acting theophylline, patients took 4 doses (24 hr.) of short-acting theophylline, prior to the study day. Tanner Stages I:13 patients, II:9, III:4, IV:4, V:9. Twenty-five patients were male, 14 female. To test the hypothesis that the increase occurs during adolescence, we studied 39 asthmatics aged 8–18y (mean 12.7). Theophylline half-life (t½ elim) is shorter in children than adults.
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