The Effect Of Different Nationalities And CYP2C9 Genetic Polymorphism In Losartan Pharmacokinetics

Objective: To investigate the pharmacokinetics of losartan and its active metabolite E-3174 in subjects of five different Chinese nationalities (Han, Mongolian, Korean, Hui and Uigur).Population modeling was performed using NONMEM (nonlinear mixed-effect modeling) program.The allele frequency of CYP2C9*2 was determined, and the impact of CYP2C9*2 genetic polymorphism on the pharmacokinetics of losartan was evaluated. This reaserch would provide instruction for the usage of losartan potassium tablets safely and reasonably for individual dosage regimens.Methods: Fifty healthy subjects (five males and five females of each ethnicity) were recruited and each received 50-mg dose of losartan in tablet form. 14 blood samples were collected for each subject over a 24-h period after drug administration. The concentrations of losartan and its active metabolite E-3174 in plasma were determined by high-performance liquid chromatography-fluorescence (HPLC-FLU) method, the pharmacokinetic parameters were calculated by DAS 2.0 software and compared by the methods of One-Way ANOVA and Nonparametric Test in SPSS 16.0 software. The combined population pharmacokinetic model for losartan and its active metabolite E-3174 was established based on the data from 50 healthy subjects of 650 samples, the covariates which might influence the pharmacokinetic characteristics of the drug and its metabolite were identified. Nonparametric bootstrap was used for the model stability validation. Polymerase chain reaction-Restriction fragment length polymorphism (PCR-RFLP)method was applied to detect the allele frequency of CYP2C9*2 genetic polymorphism in 214 Uigur and 164 Hui healthy subjects. Blood samples were collected from eight CYP2C9*1/*1 genotype Hui subjects and six CYP2C9*1/*2 genotype Hui subjects. Estimates of pharmacokinetic parameters of losartan were obtained from DAS 2.0 software. The pharmacokinetic parameters of two groups were compared by the methods of Independent-Samples T Test and Nonparametric Test in SPSS 16.0 software.Results: The pharmacokinetic parameters of losartan of Han, Mongolian, Korean, Hui and Uigur healthy subjects were as follows: Cmax: (351.0± 167.6)?(438.4±254.3)?(524.1±348.8)?(611.1±418.5) and (344.2 ±153.4) ng·mL-1;tmax: (1.34 ± 1.06)?(1.58 ±0.87)?(0.89±0.40)?(1.16±0.64) and (1.03±0.28) h; t1?2: (0.82±0.40)?(1.91 ±1.15)?(1.46±0.43)?(1.57±1.71) and (1.03±0.43) h; Vd: ( 115.2 ±43.4)?(159.3 ±93.2)?(164.8±91.7)?(139.5± 141.4)and (123.3±41.9) L; CL: (106.5±36.3)?(62.4 ±42.0)?(79.9± 38.2)?(67.7 ±17.7) and(87.4 ± 26.2)L-h-'; AUC(0-?):(523.3 ± 183.9)?(944.4 ± 338.1 )? (830.8 ± 224.9)?(853.0 ± 223.2)and (631.9 ± 242.3) ng.h·mL-1. The t1/2 values of losartan showed significant differences between Mongolian and Han. After normalization by weight, no ethnicity-based difference was noted in the pharmacokinetic parameters of losartan.The pharmacokinetic parameters of the active metabolite E-3174 of Han, Mongolian, Korean,Hui and Uigur healthy subjects were as follows: Cmax: (241.9 ±60.1)?(357.6±169.9)?(493.0±188.0)?(463.2±134.1) and (476.7±165.6) ng-mL-1; tmax: (3.60 ± 1.60)?(3.75 ±1.86)? (2.40±0.81)?(2.80±0.79) and (2.60 ±0.52) h; t1/2: (4.65 ±1.10)?(4.38±0.68)?(3.08±0.70)?(3.39±0.92) and (2.94± 0.81) h; Vd:( 170.4 ±30.5)?(127.4± 32.5)?(87.6 ±14.8)?(87.9± 17.6) and (91.8 ±32.9) L; CL: (25.7 ± 2.5)?(20.3 ± 4.9 )?(20.6 ± 5.5)?( 18.4±3.5) and(21.5±4.8) L·h-1; AUC(0?): (1960.9± 181.9)?(2602.7±668.3)?(2607.7±765.6)?(2811.4±581.4) and (2429.4± 552.4) ng·h-mL-1?The t1/2 values of Mongolian and Han showed significant differences with the other three nationalities. The Vd and Cmax values of Mongolian and Han were still significant different with the other three nationalities after weight normalization.The population pharmacokinetic (PPK) model of losartan and its active metabolite E-3174 were performed using NONMEM program, based on a two-compartment. The PPK model of losartan was established and expressed as follows:(CL10/F)i= 12.9×?RACE1,3,5-CL10×e?CL10,i(L·h-1)(V1/F)i= 29.2×?RACE4,5-V1×e?V1,i(L)(CL2/F)i=27.6×?RACE1,3,4-CL2×e?CL2,i(L·h-1)Kai?1.89×e?Ka,i(h-1)(V2/F)i?83.9×e?V2,i(L)Kti=1.25×?RACE3,4,5-Kt×e?Kt,iThe PPK model of E-3174 was established and expressed as follows:(CL3/F)i= 14.1×e?CL3,i(L·h-1)(V3/F)i=63.3×e?V3,i (L)(CL4/F)i= 14.6×e?CL4,i (L·h-1)(V4/F)i = 33.9 ×e?V4,i(L)The results showed that ethnicity factor had significant influence on the non-metabolizing E-3174 clearance CL10, the peripheral compartment clearance CL2 and the central compartment volume V1 of losartan and also has a significant effect on the transit rate (Kt).PCR-RFLP method was applied to detect the frequency of CYP2C9*2 genetic polymorphism in 214 Uigur and 164 Hui subjects. 176 CYP2C9*1/*1 genotype, 35 CYP2C9*1/*2 genotype and 3 CYP2C9*2/*2 genotype were founded in Uigur subjects. The frequency of CYP2C9*2 allele was 9.58 %. 149 CYP2C9*1/*1 genotype and 15CYP2C9*1/*2 genotype were founded in Hui subjects,no CYP2C9*2/*2 genotype was detected. The frequency of CYP2C9*2 allele was 4.57 %. The genotype frequency was consistent with Harding-Weinberg equilibrium. The pharmacokinetic parameters of losartan of CYP2C9*1/*1 genotype and CYP2C9*1/*2 genotype Hui subjects were as follows: Cmax: (498.6±226.0) and (420.3±186.5) ng·mL-1;t1/2: (1.06 ± 0.33) and (1.39 ± 0.43) h;AUC(0-24): (903.4±286.2) and (946.3 ± 349.3) ng·h-mL-1; AUC(0?): (946.8± 307.0) and (996.0±332.1) ng·h·mL-1. The pharmacokinetic parameters of E-3174 were as follows: Cmax: (389.4±109.7)and (237.5 ±90.6) ng·mL-1; t1/2: (3.84± 0.70) and (4.79 ± 1.25) h; AUC(0-24): (2378.4 ± 490.1) and(1744.0 ± 431.9) ng h mL-1; AUC(0-?) (2420.9± 494.0) and (1828.0 ± 457.3) ng·h·mL-1. After the comparison by SPSS 16.0 software, the results showed that there were significant differences in AUC(0-24)?AUC(0-?) and Cmax of E-3174 between CYP2C9*1/*1 genotype and CYP2C9*1/*2 genotype Hui subjects.Conclusions: Ethnicity factor had significant impact on the pharmacokinetics of losartan and its metabolite E-3174 after a single oral dose in healthy subjects of the five different nationalities in China to a certain extent. The PPK models were steady and reliable. Ethnicity factor showed significant influence on both losartan clearance and the transition from losartan to E-3174. Therewere significant difference of pharmacokinetics of losartan between the CYP2C9*1/*1 genotypegroup and CYP2C9*1/*2 genotype group, the CYP2C9*1/a*2 may decrease the generation of E-3174.