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In vivo modulation of CYP enzymes by quinidine and rifampin
Author(s) -
Branch Robert A.,
Adedoyin Adedayo,
Frye Reginald F.,
Wilson John W.,
Romkes Marjorie
Publication year - 2000
Publication title -
clinical pharmacology and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.941
H-Index - 188
eISSN - 1532-6535
pISSN - 0009-9236
DOI - 10.1067/mcp.2000.110561
Subject(s) - quinidine , pharmacology , enzyme , debrisoquine , mephenytoin , in vivo , cytochrome p450 , rifampicin , cyp2d6 , chemistry , drug metabolism , drug , drug interaction , enzyme inducer , biochemistry , biology , cyp2c19 , microbiology and biotechnology , antibiotics
Background The metabolism of drugs and other xenobiotics is mediated by enzymes whose activities can be modulated by different compounds. The activities of these modulators have the potential to be used to optimize drug action, prevent toxicity, or identify the enzymes involved in a reaction. This approach requires that selective agents be used for specific enzymes. However, selectivity of action has been poorly characterized in vivo. Methods This study investigated the effect of 3 and 28 days of treatment with quinidine (200 mg daily) and rifampin (INN, rifampicin) (600 mg daily) on the activities of four cytochrome P450 enzymes and N ‐acetyltransferase in 28 healthy young male volunteers divided into three groups with a cocktail of drug probes used, including caffeine, mephenytoin, debrisoquin (INN, debrisoquine), and dapsone. Results Quinidine selectively and almost completely inhibited the activity of CYP2D6 from day 3 through day 28 without affecting any other enzymes. Rifampin showed evidence of time‐dependent induction of the activities of all measured oxidative routes of metabolism but decreased the acetylation ratio in fast acetylators. The quinidine/rifampin combination resulted in selective CYP2D6 inhibition and induction of all other enzymes evaluated over this time period, suggesting that predictable complex interactions occur with the drug combination. Conclusions These observations illustrate the value of simultaneous assessment of the effect of modulators on the activities of multiple specific enzymes with the drug cocktail approach. (Clin Pharmacol Ther 2000;68:401‐11.) Clinical Pharmacology & Therapeutics (2000) 68 , 401–411; doi: 10.1067/mcp.2000.110561