| Lansoprazole (LPZ) that has been widely used for the treatment of acid-related diseases is a relatively novel class of proton pump inhibitors (PPIs). The hydroxylation of LPZ (OH-LPZ formation) by cytochrome P450 (CYP) 2C19 is the main metabolic route. The activity of CYP2C19 depends significantly on the CYP2C19 genotype status. This leads the marked kinetic difference of LPZ. Therefore, we studied the kinetic characteristics of LPZ in subjects who had different genotype status and intended to supply the basis of pharmacokinetics for the dose regimen of LPZ , based on identification of genotypes .Methods1. Genotyping procedures for CYP2C 19: Venous blood samples (2ml each) wereobtained from 70 unrelated healthy Chinese Han subjects. The proportion of men and women was 44/26.Their mean age was 22 years (range, 19~26 years). The genome DNA were extracted by classic SDS-proteinase K-hydroxybenzene-chloroform methods from blood. Though regular polymerase chain reaction (PCR) amplification, electrophoresis on 2% agarose gel and EB-staining, we observed and analyzed the specific segments of C YP2C 1 9m 1 in exon 5 and C YP2C 1 9m2 in exon 4 , associated with the poor metabolizer phenotype. Using 50 bp DNA ladder as DNA marker in ultraviolet transilluminator. From these performances, the chosen good samples went on beingdigested with restriction endonuclear enzyme BamHI -, Sma I separately . After electrophoresis on 4% agarose gel, took pictures using numeric camera and saved it in computer. We coded the bands in different number: 1 expressed wt/wt genotype type, 2 expressed wt/ml type, 3 expressed wt/m2 type, 4 expressed ml/ml type, 5 expressed ml/m2 type homozygote, 6 expressed m2/m2 type and inputed SPSS 10.0 to classify and analyse.2 . The study for pharmacokinetics in subjects based on identification of genotypes: 18 unrelated healthy Chinese subjects were recruited from a total of 70 subjects. 9 of them were homozygous for the wild-type (wt) allele in both exon 5 and exon 4 (wt/wt) and classified as the homozygous extensive metabolizers (hoEMs) group. Another 9 of them were classified as the poor metabolizers (PMs) group, they were heterozygous for the two defects (ml/m2) or homozygous for the ml mutation without the m2 mutation (ml/ml). None of the subjects had a history of significant medical illness or hypersensitivity to any drugs . They did not consume extensive amounts of alcohol and were non-smokers. None of them had taken any other drugs for at least 2 week before the study and did not take any other drugs during the study. Their normal health status was judged on the basis of a physical examination with screening blood chemistries, including a complete blood count and liver function test, urinalysis and electrocardiogram performed before the study. After an overnight fast, each of them received an oral dose of 30 mg lansoprazole as the enteric-coated formulation with 200ml water. A standardized meal was served separately at 4 hours and 10 hours after the drug ingestion. Venous blood samples (4ml each) were collected into heparinized tubes, immediately before the drug administration and at 0.5, 1, 1.5, 2, 3, 4, 5, 6, 8, 10, 12, 24 hours after dosing. The samples were spun immediately after the collection, and the plasma samples were stored at -20C until assayed . the plasma concentrations of lansoprazole were determined by reversed high-performance liquid chromatography (HPLC) with DAD detection according to an analytical method developed. The plasma concentration-time data were disposed with 3p97 program. The peak concentration (Cmax) and the peak time (Tmax) of lansoprazole were determined from the respective observed concentration-time data, The area under the curve (AUC) were calculated by the lineartrapezoidal method. The data are expressed as mean valueslSEM throughout the paper. Difference in pharmacokinetic data between the extensive metabolizer and poor metabolizer groups were evaluated statistically by use of a two-sample t test. P value of <0.05 was considered...
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