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CYP3A4 genetic polymorphism influences repaglinide's pharmacokinetics

Ruzilawati AB, Gan SH

Pharmacology, 2010;85(6):357-64.
PMID: 20523106 DOI: 10.1159/000302731

AIM: To investigate the effects of CYP3A4 and CYP2C8 enzymes on repaglinide's pharmacokinetics in healthy Malaysian subjects.
METHODS: Subjects (n = 121) received oral repaglinide (4 mg). Blood samples were taken at 0, 30, 60, 120, 180 and 240 min and serum concentrations of repaglinide were determined using high-performance liquid chromatography. Subjects were also genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) for CYP3A4*4, *5 and*18 and by an allele-specific multiplex PCR for CYP2C8*2, *3, *4 and *5 alleles.
RESULTS: The allele frequencies of CYP2C8*1, *2, *3, *4 and *5 were 95.04, 0.40, 0.40, 0 and 4.13%, respectively. The frequencies of the CYP3A4*1, *4, *5 and *18 alleles were 97.93, 0, 0 and 2.07%, respectively. CYP2C8 and CYP3A4 genotypes were not significantly associated with repaglinide's blood glucose-lowering effect. However, the CYP3A4 genotype significantly influenced some of repaglinide's pharmacokinetics, where the mean elimination rate constant was 44.0% lower (p = 0.04) and the mean half-life was 33.8% higher (p = 0.04) in subjects with the CYP3A4*1/*18 genotype as compared to those with the normal CYP3A4*1/*1 genotype. This result confirms that CYP3A4 plays a large role in metabolizing repaglinide.
CONCLUSION: Genetic polymorphisms of CYP3A4, specifically CYP3A4*18, play a major role in contributing to the interindividual variability in repaglinide's pharmacokinetics.
Population pharmacokinetic modelling of repaglinide in healthy volunteers by using Non-Parametric Adaptive Grid Algorithm

Ruzilawati AB, Mohd Suhaimi AW, Gan SH

J Clin Pharm Ther, 2010 Feb;35(1):105-12.
PMID: 20175819 DOI: 10.1111/j.1365-2710.2009.01042.x

To estimate population pharmacokinetic parameters of repaglinide in 121 healthy Malaysian volunteers.
Genetic polymorphisms of CYP3A4: CYP3A4*18 allele is found in five healthy Malaysian subjects

Ruzilawati AB, Suhaimi AW, Gan SH

Clin Chim Acta, 2007 Aug;383(1-2):158-62.
PMID: 17601520 DOI: 10.1016/j.cca.2007.05.004

BACKGROUND: Cytochrome P450 3A4 (CYP3A4) is the major cytochrome involved in metabolizing of >60% of all drugs used in humans. A number of allelic variations in CYP3A4 gene are known to affect catalytic activity including CYP3A4*4, CYP3A4*5 and CYP3A4*18. We investigated the frequencies of CYP3A4*4, CYP3A4*5 and CYP3A4*18 alleles in a Malaysian population. This will impact treatment of patients receiving drugs metabolized by these alleles.

METHODS: The study was conducted in 121 healthy Malaysian volunteers. DNA was extracted from leucocytes and the 3 alleles were determined by PCR-RFLP. The PCR product was later digested with restriction enzymes BstMA I, BshV I and Hpa II.

RESULTS: No mutations were detected for CYP3A4*4 and CYP3A4*5 alleles. The frequency of the CYP3A4*18 allele in the Malaysian population is 2.1%. All 5 subjects with CYP3A4*18 mutations were found to be heterozygous.

CONCLUSION: The present study describes polymorphisms of CYP3A4 among Malaysian subjects. Clinical relevance of these genetic variants in these healthy volunteers is under investigation.
Method development and validation of repaglinide in human plasma by HPLC and its application in pharmacokinetic studies

Ruzilawati AB, Wahab MS, Imran A, Ismail Z, Gan SH

J Pharm Biomed Anal, 2007 Apr 11;43(5):1831-5.
PMID: 17240100

In this study, the development and validation of a high-performance liquid chromatography (HPLC) assay for determination of repaglinide concentration in human plasma for pharmacokinetic studies is described. Plasma samples containing repaglinide and an internal standard, indomethacin were extracted with ethylacetate at pH 7.4. The recovery of repaglinide was 92%+/-55.31. Chromatographic separations were performed on Purospher STAR C-18 analytical column (4.8 mm x 150 mm; 5 microm particle size). The mobile phase composed of acetonitrile-ammonium formate (pH 2.7; 0.01 M) (60:40, v/v). The flow rate was 1 ml/min. The retention time for repaglinide and indomethacin were approximately 6.2 and 5.3 min, respectively. Calibration curves of repaglinide were linear in the concentration range of 20-200 ng/ml in plasma. The limits of detection and quantification were 10 ng/ml and 20 ng/ml, respectively. The inter-day precision was from 5.21 to 11.84% and the intra-day precision ranged from 3.90 to 6.67%. The inter-day accuracy ranged 89.95 to 105.75% and intra-day accuracy ranged from 92.37 to 104.66%. This method was applied to determine repaglinide concentration in human plasma samples for a pharmacokinetic study.
Fulltext Cytokine (IL-10, IL-6, TNF-α and TGF-β1) Gene Polymorphisms in Chronic Hepatitis C Virus Infection among Malay Male Drug Abusers

Noh IC, Ahmad I, Suraiya S, Musa NF, Nurul AA, Ruzilawati AB

Biomedicines, 2021 Aug 30;9(9).
PMID: 34572300 DOI: 10.3390/biomedicines9091115

Cytokines play an important role in modulating inflammation during viral infection, including hepatitis C virus (HCV) infection. Genetic polymorphisms of cytokines can alter the immune response against this infection. The objective of this study was to investigate the possible association between chronic hepatitis C virus infection susceptibility and cytokine gene polymorphism for interleukin-10 (IL-10) rs1800896 and rs1800871, interleukin 6 (IL-6) rs1800795, TNF-α rs1800629, and TGF-β1 rs1800471 in Malay male drug abusers. The study was conducted on 76 HCV-positive (HP) male drug abusers and 40 controls (HCV-negative male drug abusers). We found that there were significant differences in the frequencies of genotype for IL-10 rs1800871 (p = 0.0386) and at the allelic level for IL-10 rs1800896 A versus G allele (p = 0.0142) between the HP group and the control group. However, there were no significant differences in gene polymorphism in interleukin 6 rs1800795, TNF-α rs1800629 and TGF-β1 rs1800471. These findings suggest significant associations between gene polymorphism for IL-10 rs1800871, IL-10 rs1800896 (at the allelic level) and susceptibility to HCV infection among Malay male drug abusers.