Affiliation:
1. Laboratory of Chemical Pharmacology, National Heart and Lung Institute, N.I.H., Bethesda, Md 20205, USA
2. Department of Biochemical and Experimental Pharmacology, St Mary's Hospital Medical School, Paddington, London, W2 1PG
Abstract
Abstract
The metabolism and pharmacokinetics of intravenously administered theophylline and aminophylline (theophylline ethylenediamine) have been studied in 3 volunteers, using 14C-labelled theophylline. Both compounds were metabolized extensively and 1, 3-dimethyl-uric acid, 1-methyluric acid, 3-methylxanthine and two unknown minor metabolites were excreted in the urine, in addition to theophylline. The elimination of theophylline, 1, 3-dimethyluric acid, 1-methyluric acid and the unknown metabolites followed first-order kinetics, but that of 3-methylxanthine followed Michaelis-Menten kinetics. When given as aminophylline, theophylline was metabolized more rapidly and extensively than when given alone. The recovery of 14C in the urine was significantly higher after aminophylline than after theophylline. Abstention from intake of dietary methylxanthines for 7 days resulted in more rapid and extensive metabolism of aminophylline compared with results from the same subjects on their usual diets. The results indicate that, from a metabolic and pharmacokinetic viewpoint, aminophylline and theophylline are not equivalent.
Publisher
Oxford University Press (OUP)
Subject
Pharmaceutical Science,Pharmacology
Cited by
21 articles.
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