A novel transversion in the intron 5 donor splice junction of CYP2C19 and a sequence polymorphism in exon 3 contribute to the poor metabolizer phenotype for the anticonvulsant drug S-mephenytoin.
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Ibeanu GC, Blaisdell J, Ferguson RJ, Ghanayem BI, Brosen K, Benhamou S, Bouchardy C, Wilkinson GR, Dayer P, Goldstein JA
A novel transversion in the intron 5 donor splice junction of CYP2C19 and a sequence polymorphism in exon 3 contribute to the poor metabolizer phenotype for the anticonvulsant drug S-mephenytoin.
J Pharmacol Exp Ther. 1999 Aug;290(2):635-40.
- PubMed ID
- 10411572 [ View in PubMed]
- Abstract
Cytochrome P-450 (CYP) 2C19 is responsible for the metabolism of a number of therapeutic agents such as S-mephenytoin, omeprazole, proguanil, certain barbiturates, diazepam, propranolol, citalopram and imipramine. Genetic polymorphisms in this enzyme are responsible for the poor metabolizers (PM) of mephenytoin, which represent approximately 13-23% of Asians and 3-5% of Caucasians. Several polymorphisms contribute to this phenotype. We have isolated two new allelic variants that contribute to the PM phenotype in Caucasians. CYP2C19*7 contained a single T --> A nucleotide transversion in the invariant GT at the 5' donor splice site of intron 5. The second PM allele, CYP2C19*8, consisted of a T358C nucleotide transition in exon 3 that results in a Trp120Arg substitution. In a bacterial expression system, CYP2C198 protein exhibited a dramatic (approximately 90% and 70%) reduction in the metabolism of S-mephenytoin and tolbutamide, respectively, when compared with the wild-type CYP2C191B protein. Restriction fragment length polymerase chain reaction tests were developed to identify the new allelic variants.
DrugBank Data that Cites this Article
- Polypeptides
Name UniProt ID Cytochrome P450 2C19 P33261 Details - Pharmaco-genomics
Drug Interacting Gene/Enzyme Allele name Genotypes Defining change(s) Type(s) Description Details Mephenytoin Cytochrome P450 2C19
Gene symbol: CYP2C19
UniProt: P33261CYP2C19*8 (C;C) / (C;T) - T > C (rs41291556)
Effect Directly Studied Patients with this genotype have reduced metabolism of mephenytoin. Details Mephenytoin Cytochrome P450 2C19
Gene symbol: CYP2C19
UniProt: P33261CYP2C19*7 (A;A) / (A;T) - T > A (rs72558186)
Effect Directly Studied Patients with this genotype have reduced metabolism of mephenytoin. Details Amitriptyline Cytochrome P450 2C19
Gene symbol: CYP2C19
UniProt: P33261CYP2C19*7 Not Available - 19294T>A (rs72558186)
ADR Inferred Those with the AA or AG genotype are poor metabolizers of amitriptyline Details Omeprazole Cytochrome P450 2C19
Gene symbol: CYP2C19
UniProt: P33261CYP2C19*7 Not Available - 19294T>A (rs72558186)
Effect Inferred Poor metabolizer, lower dose requirement, improved drug efficacy Details Clobazam Cytochrome P450 2C19
Gene symbol: CYP2C19
UniProt: P33261CYP2C19*7 Not Available - 19294T>A (rs72558186)
ADR Inferred Clobazem is metabolized into N-desmethylclobazem (NCLB) mostly by CYP3A4. NCLB is primarily metabolized by 2C19. Those with one 2C19*2 allele mutation (1*/2*) are intermediate metabolizers of NCLB. Those with two (2*/2*) mutations will metabolize NCLB poorly in comparisone to extensive metabolizers (1*/1*). Levels of NCLB can be five times higher in poor metabolizers, and two times higher in intermediate metabolizers as compared to individuals who are extensive metabolizers. The safety and efficacy of clobazem may be affected by polymorphic expression of CYP2C19*2. Details Lansoprazole Cytochrome P450 2C19
Gene symbol: CYP2C19
UniProt: P33261CYP2C19*7 Not Available - 19294T>A (rs72558186)
Effect Inferred Poor metabolizer, lower dose requirement, improved drug efficacy Details Mephenytoin Cytochrome P450 2C19
Gene symbol: CYP2C19
UniProt: P33261CYP2C19*7 Not Available - 19294T>A (rs72558186)
Effect Inferred Poor metabolizer, lower dose requirement Details Esomeprazole Cytochrome P450 2C19
Gene symbol: CYP2C19
UniProt: P33261CYP2C19*7 Not Available - 19294T>A (rs72558186)
Effect Inferred Poor metabolizer, lower dose requirement, improved drug efficacy Details Clopidogrel Cytochrome P450 2C19
Gene symbol: CYP2C19
UniProt: P33261CYP2C19*7 Not Available - 19294T>A (rs72558186)
Effect Inferred Poor drug metabolizer, lower dose requirements, higher risk for drug-drug interactions Details Proguanil Cytochrome P450 2C19
Gene symbol: CYP2C19
UniProt: P33261CYP2C19*7 Not Available - 19294T>A (rs72558186)
Effect Inferred Poor metabolizer, lower dose requirement Details Gliclazide Cytochrome P450 2C19
Gene symbol: CYP2C19
UniProt: P33261CYP2C19*7 Not Available - 19294T>A (rs72558186)
Effect Inferred Poor drug metabolizer. Details