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Theophylline‐rifampicin interaction: non‐selective induction of theophylline metabolic pathways.
Author(s) -
Robson RA,
Miners JO,
Wing LM,
Birkett DJ
Publication year - 1984
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.1365-2125.1984.tb02487.x
Subject(s) - theophylline , rifampicin , pharmacology , chemistry , metabolism , drug interaction , cytochrome p450 , drug metabolism , metabolic pathway , pharmacokinetics , demethylation , medicine , endocrinology , biochemistry , antibiotics , gene expression , dna methylation , gene
The effect of rifampicin pre‐treatment (600 mg daily for 6 days) on theophylline disposition at steady state was investigated in six healthy males. Following rifampicin treatment total plasma clearance of theophylline increased by 82%. Theophylline clearance through each metabolic pathway was increased, 1‐demethylation by (116 +/‐ 34%) (mean +/‐ s.e. mean), 3‐demethylation by (91 +/‐ 16%) and 8‐oxidation by (81 +/‐ 17%). Renal clearance of unchanged drug was not altered. Previous studies have suggested that two forms of cytochrome P‐450 are involved in theophylline metabolism, one mediating the N‐demethylations and the other 8‐oxidation. Thus, unlike the selective inductive effect of rifampicin on antipyrine metabolic pathways, rifampicin does not differentially affect those forms of cytochrome P‐450 involved in theophylline metabolism. The extent to which theophylline metabolism is induced by rifampicin is likely to have important clinical consequences.