Study On Population Pharmacokinetics Of Carbamazepine And On Genetic Polymorphism Of Metabolic Enzyme CYP3A4

Carbamazepine(CBZ), as one of the most important anti-epileptic agent, is widely used in preventing general rigidity—clonic seizure and partial seizure. Because of the narrow therapeutic window (4--12 mg·L-1), the large individual variation of different patients response to CBZ and the serious adverse reaction, doctors adjust the dosage of CBZ by monitoring its trough serum concentration. But monitoring the trough serum concentration can't predict patients' response to CBZ before taking. It is helpless to determine the initial dose and long-term maintain dose. Now, there are two kind of studies on determining rational individual regimen for drugs. One is population pharmacokinetics (PPK) study. The PPK study can investigate the factors that affect drug metabolism, illustrate the variability of pharmacokinetic of therapeutic drugs in a diverse population and obtain ideal individual PK parameters. The second study is pharmacogenomics. The candidate genes that affects drug metabolism are selected out by pharmacogenomics.Then we can investigate the relations between genetic polymorphism and clinical phenotype (such as trough serum concentration, curative effect et al). It provides a more reliable basis for individual therapy by learning the genotype of different patients.We collected the monitoring results of CBZ serum concentrations retrospectively from September 2007 to September 2008.The CBZ serum concentrations were determined in Shanxi Medical University the Second Hospital clinical pharmacy laboratory. The study analyzes the relations between age, gender, treated with other drugs and serum concentrations, and between serum concentrations and curative effect. We also collected the monitoring results of CBZ serum concentrations and the general demographic information of the patients, including age,gender,weight,dosage,time and co-administration from October 2008 to September 2009. The population phamacokinetics model of carbamazepine in patients with epileptic was built using nonlinear mixed effect model. The influence of the general demographic information on PK parameters of CBZ was investigated. We also collected 141 whole blood samples of the epileptic patients treated with CBZ, determined the CYP3A4 genetic polymorphism, investigated the influence of CYP3A4 genetic polymorphism on CBZ metabolism. It provides a more reliable basis for the rational individual regimen for CBZ.Part one:Monitoring results of blood concentration of carbamazepine in 189 cases with epilepticMaterials:We collected the monitoring results of blood concentration of carbamazepine in patients with epileptic and detailed information associated with these patients from October 2008 to September 2009. All the patients were monitored in the clinical pharmacy laboratory of Shanxi Medical University the Second Hospital.Methods:The blood concentration of carbamazepine were determined by the method of fluorescence polarization immunassay(FPIA). The principle of FPIA:According to the principle of competition-binding assay, the antigen in the specimens and a certain amount of fluorescent labeled antigen combine with antibody competitively. If the antigen in the specimens is more, the fluorescent labeled antigen combined with antibody is less. Thus the measured fluorescence polarization luminosity is also less. So the measured blood concentration is greater accordingly. Comparing the effective rate between the group of only using CBZ and the group of using CBZ and other antiepileptic drugs by SPSS 11.0. The evaluation criteria are divided into completely control, effective and invalid.Results:(1) The percentage of the blood concentration of CBZ reached the therapeutic window in the group of 1 year,1-3 years old,4-12 years old and 13-18 years old are 0,50.0%, 81.3% and 93.2% respectively. The percentage of the blood concentration of CBZ reached the therapeutic window is higher along with increasing age.(2) The blood cencentration of 32 cases was less than 4 mg·L-1,among them 20 cases were effective(62.5%);2cases were more than 12 mg·L-1,2cases were effective(100%);the concentration of 155 cases was 4--12 mg·L-1, among them 114 cases were effective(73.5%). The effective rate of CBZ blood concentration reached the therapeutic window is higher than under the therapeutic window.(3) The percentage of CBZ blood concentration reached the therapeutic window is 79.3% when the epileptic patients received CBZ and Chinese traditional medicine; The percentage is 87.8% when the epileptic patients received CBZ and TMP; The percentage is 90.9% when the epileptic patients received CBZ and VPA.(4) The chi square test results of comparing the effective rate between the group of only using CBZ and the group of using CBZ and other antiepileptic drugs show no statistically significant(P>0.05). We don't think the effective rate of the two groups is different.Part two:Population phamacokinetics of carbamazepine in patients with epilepticMaterials:We collected the monitoring results of blood concentration of carbamazepine from October 2008 to September 2009. All the patients were monitored in the clinical pharmacy laboratory of Shanxi Medical University the Second Hospital. We also collected the general demographic information of the patients with epileptic, including age,gender,weight,dosage,time and adverse reaction. We got 316 CBZ blood concentrations of 270 patients with epileptic. Method:The blood concentrations of carbamazepine were determined using the method of part one. The population phamacokinetics model of carbamazepine in patients with epileptic was built using nonlinear mixed effect model. The influence of the general demographic information on PK parameters of CBZ was investigated. Bootstrap was applied to validate the PPK model.Results:(1) Age,dose and weight are the factors that affect the clearance of CBZ.(2)The final models of CBZ were:CL (L/h)=[2.55+0.013×(AGE-15)]×(DKG/.011)0.443×(BW/40)0.392 as age<=14; when age>14, CL (L/h)=2.55×(DKG/.011)0.443×(BW/40)0.392。Vd=85L。(3) The model was stable and reliable by bootstrap.Part three:Genetic polymorphism of CYP3A4 in epileptic patients treated with CBZMaterials:We collected the whole blood samples of the epileptic patients treated with CBZ from October 2008 to September 2009. All the patients were monitored in the clinical pharmacy laboratory of Shanxi Medical University the Second Hospital. A total of 141 samples were collected. Gender height and weight of the epileptic patients were not limited. All the epileptic patients are Han people, normal hepatic and renal function, without other complications.87cases were male and 54 cases were female. The span of age is 1—46.Method:Genemic DNA was extracted from whole blood samples according to the directions of SE blood DNA kit(OMEGA). CYP3A4 genotype was determined by polymerase chain reaction—restriction fragment length polymorphism.Results:In 141 whole blood samples, we find out 1 CYP3A4*4 mutation and 1 CYP3A4*6 mutation. The gene frequencys of CYP3A4*4,*5 and *6 were 1/141,0 and 1/141,respectively.Conclusions:(1) The individual variation of different patients response to CBZ is tremendous. Manifested in two aspects:①Although patients with similar physiological conditions received the same dose of CBZ, the variation of the blood concentrations is large.②The blood concentrations of the epileptic patients is same, but the variation of curative effect is large. Monitoring the blood concentration is only the basis of adjusting the dosage of CBZ.(2) The PPK model of CBZ showed good stability and it can be used to estimate the relative clearance of CBZ. It is very helpful to determine the initial dose and maintain dose for doctors.(3) The conclusion that CYP3A4 genetic mutation could influence CBZ metabolism is still not sure in my study.(4) We only find out two cases of CYP3A4 genetic mutation, so we can't introduce the factor of genetic polymorphism into the PPK model. We need to enlarge the samples for the further study.