Effects of allopurinol on theophylline metabolism and clearance

John J. Grygiel, Lindon M.H. Wing, Julie Farkas, Donald J. Birkett

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    92 Citations (Scopus)


    The effects of allopurinol on the plasma clearance and metabolism of'theophylline in man were investigated under single-dose and multiple-dosing conditions. No change in theophylline clearance was found with the concomitant use of allopurinol but 1-methylxanthine (IMX), a theophylline metabolite not previously described in man, was detected in urine during control and allopurinol treatment phases under both single- and multiple-dosing conditions. IMX excretion increased at the expense of 1-methyluric acid (IMU) during the allopurinol treatment phase. It is proposed that the secondary biotransformation of IMX to IMU is mediated by xanthine oxidase.

    Original languageEnglish
    Pages (from-to)660-667
    Number of pages8
    JournalClinical Pharmacology and Therapeutics
    Issue number5
    Publication statusPublished - Nov 1979


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