Metabolism of theophylline to caffeine in adults
Tang-Liu, D.D.; Riegelman, S.
Research Communications in Chemical Pathology and Pharmacology 34(3): 371-380
1981
ISSN/ISBN: 0034-5164 PMID: 7323439 Document Number: 175027
Caffeine and its major metabolite, paraxanthine, were observed in plasma following oral administration of theophylline in a multiple dose study. At steady state, plasma caffeine concentrations varied from 0.21-0.75 mg/l at plasma theophylline concentrations of 8.1-21.5 mg/l in 4 healthy subjects. About 6% of the theophylline dose was converted to caffeine, which is further metabolized to a series of degradation products. The undetectable urinary excretion of these degradation products, which can be measured after caffeine administration, accounted for the incomplete urinary recovery usually observed after theophylline administration.