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1‐Methylxanthine derived from theophylline as an in vivo biochemical probe of allopurinol effect.
Author(s) -
Birkett DJ,
Miners JO,
Day RO
Publication year - 1991
Publication title -
british journal of clinical pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.216
H-Index - 146
eISSN - 1365-2125
pISSN - 0306-5251
DOI - 10.1111/j.1365-2125.1991.tb03888.x
Subject(s) - theophylline , metabolite , allopurinol , in vivo , pharmacology , pharmacokinetics , medicine , endocrinology , chemistry , biology , microbiology and biotechnology
The urinary 1‐methyluric acid (1MU) to 1‐methylxanthine (1MX) ratio has been assessed as a biochemical index of oxipurinol effect in vivo in man. Dosing with theophylline was used to produce 1MX as an intermediate metabolite in six healthy volunteers. A sigmoid Emax model was fitted to the data and gave a mean plasma oxipurinol IC50 of 3.0 +/‐ 1.1 mg l‐1, a mean exponent n of 3.4 +/‐ 2.1 and a mean IC90 of 8.5 +/‐ 5.9 mg l‐1. There was marked interindividual variability in the steepness of the plasma oxipurinol concentration response relationship, and in the plasma oxipurinol IC90 values. The study has confirmed the feasibility of using single doses of allopurinol to construct individual plasma oxipurinol concentration‐response curves.