Isoniazid is a mechanism-based inhibitor of cytochrome P450 1A2, 2A6, 2C19 and 3A4 isoforms in human liver microsomes.
Article Details
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Wen X, Wang JS, Neuvonen PJ, Backman JT
Isoniazid is a mechanism-based inhibitor of cytochrome P450 1A2, 2A6, 2C19 and 3A4 isoforms in human liver microsomes.
Eur J Clin Pharmacol. 2002 Jan;57(11):799-804.
- PubMed ID
- 11868802 [ View in PubMed]
- Abstract
OBJECTIVE: In order to evaluate the inhibitory effects of isoniazid on cytochrome P450 (CYP) mediated drug metabolism, the in vitro inhibitory potency and specificity as well as the reduced nicotinamide adenine dinucleotide phosphate (NADPH)-, time- and concentration dependency of isoniazid as an inhibitor of the activity of the major human CYP isoforms were studied. METHODS: Using pooled human liver microsomes, the in vitro inhibitory effects of isoniazid on CYP1A2 (phenacetin O-deethylation), CYP2A6 (coumarin 7-hydroxylation), CYP2C9 (tolbutamide hydroxylation), CYP2CI9 (S-mephenytoin 4'-hydroxylation), CYP2D6 (dextromethorphan O-demethylation), CYP2E1 (chlorzoxazone 6-hydroxylation) and CYP3A4 (midazolam 1'-hydroxylation) activities were examined. RESULTS: After a 15-min preincubation without NADPH, isoniazid reversibly inhibited microsomal CYP2C19- and CYP3A4-mediated reactions with apparent Ki values of 36 microM and 73 microM, respectively. However, isoniazid had only weak inhibitory effects on the five other CYP-mediated reactions (Ki > 110 microM). After a 15-min preincubation with NADPH, isoniazid showed an increased inhibitory potency toward CYP1A2, CYP2A6, CYP2C19 and CYP3A4 activities (Ki = 56, 60, 10 and 36 microM, respectively). In addition, the inactivation of CYP1A2, CYP2A6, CYP2C19 and CYP3A4 by isoniazid was NADPH-, time- and concentration dependent, and was characterised by Kinact values of 0.11, 0.13, 0.09 and 0.08 min(-1), and K1 values of 285, 173, 112 and 228 microM, respectively. CONCLUSIONS: As the peak plasma concentrations of isoniazid are around 30-50 microM, isoniazid at clinically relevant concentrations reversibly inhibits CYP2C19 and CYP3A4 activities, and mechanistically inactivates CYP1A2, CYP2A6, CYP2C19 and CYP3A4 in human liver microsomes. Co-administration of isoniazid and drugs that are primarily metabolised by these CYP isoforms, particularly by CYP2C19 and CYP3A4, may result in significant drug interactions.
DrugBank Data that Cites this Article
- Drug Enzymes
Drug Enzyme Kind Organism Pharmacological Action Actions Isoniazid Cytochrome P450 1A2 Protein Humans UnknownInhibitorDetails Isoniazid Cytochrome P450 2A6 Protein Humans UnknownInhibitorDetails - Drug Interactions
Drugs Interaction Integrate drug-drug
interactions in your softwareAminophyllineIsoniazid The serum concentration of Aminophylline can be increased when it is combined with Isoniazid. BromotheophyllineIsoniazid The serum concentration of Bromotheophylline can be increased when it is combined with Isoniazid. CaffeineIsoniazid The serum concentration of Caffeine can be increased when it is combined with Isoniazid. DyphyllineIsoniazid The serum concentration of Dyphylline can be increased when it is combined with Isoniazid. LomifyllineIsoniazid The serum concentration of Lomifylline can be increased when it is combined with Isoniazid.