Pharmacokinetic Parameters Of Metoprolol Research Articles

Effects of Astragaloside IV on the Pharmacokinetics of Metoprolol in Rats and its Mechanism.

Astragaloside IV (AST) and metoprolol are often used together to treat cardiovascular diseases, while the herb-drug interaction (HDI) between them is still unclear. This study investigates the effect of AST on the pharmacokinetics of metoprolol in rats and its mechanism to predict the HDI. First, IC50 value of AST on nine CYP450 enzymes in human liver microsomes (HLMs) was determined by the cocktail method. We explored the effect of AST on the pharmacokinetics of metoprolol (metabolized by CYP2D6) in vivo. Twelve male SD rats were equally divided into two groups, with or without pretreatment of AST (3 mg/kg/day) for 7 days, and they received metoprolol (27 mg/kg) by oral administration. Blood samples were determined using HPLC. Finally, the mechanism of AST was explored. AST exhibited a moderate inhibitory effect on CYP2D6 with IC50 value of 32.28 μM. The pharmacokinetic parameters of metoprolol were significantly altered by AST with the increase of AUC0-∞ (538.81 ± 51.41 to 1088.34 ± 86.46 μg*min/mL, P<0.05) and Cmax (6.21 ± 0.56 to 8.34 ± 0.87 μg/ml, P<0.05). The investigation of the mechanism showed AST to be an irreversible inhibitor of CYP2D6 with KI value of 2.9 μM and Kinact of 0.018 min-1, respectively. AST was found to increase the plasma exposure of metoprolol in rats. AST reduced the metabolism of metoprolol by inhibiting CYP2D6 activity. The HDI might enhance when metoprolol and AST will be applied in combination.

Evaluation of impact of Herba Erigerontis injection, a Chinese herbal prescription, on rat hepatic cytochrome P450 enzymes by cocktail probe drugs

Ethnopharmacological relevanceHerba Erigerontis injection (HEI), one of the most popular herbal prescription in China, is made from the aqueous extracts of Erigeron breviscapus whole plant. Now HEI is widely used for the treatment of cardiovascular diseases and cerebrovascular diseases such as coronary heart disease, anginapectoris and paralysis. Aim of the studyThe purpose of this study was to investigate the in vivo effect of HEI on rat cytochrome P450 enzymes (CYP1A2, CYP2C11, CYP2D4, CYP2E1 and CYP3A2) to assess its safety through its potential to interact with co-administered drugs. Materials and methodsRats were randomly divided into five groups. Rats were intravenous administrated with HEI via the caudal vein at the dosage of 1.8ml/kg or 7.2ml/kg once daily for consecutive 3 days or 14 days. On the fourth or the fifteenth day, a cocktail solution at a dose of 5ml/kg, which contained caffeine (2.5mg/kg), tolbutamide (2.5mg/kg), chlorzoxazone (5mg/kg), midazolam (5mg/kg) and metoprolol (10mg/kg), was injected via the lingual vein to all rats. Then 0.8ml blood samples were collected at a set of time-points. The plasma concentrations of probe drugs were simultaneously determined by HPLC. Pharmacokinetic parameters simulated by DAS software were used for the evaluation of HEI on the activities of rat CYP1A2, CYP2C11, CYP2D4, CYP2E1 and CYP3A2 enzymes. ANOVA and Dunnett's test was used for data analysis. ResultsThere were no significant influence of pharmacokinetic parameters of caffeine, tolbutamide and chlorzoxazone in HEI pretreated rats. But many pharmacokinetic parameters of metoprolol and midazolam in HEI pretreated rats were affected significantly (P<0.05), which indicated that metabolism of metoprolol and midazolam in these treatment groups was evidently slowed down. ConclusionsThe results from the present in vivo study suggested that HEI showed no effects on rat CYP1A2, CYP2C11 and CYP2E1, however, it demonstrated potential inhibitory effects on rat CYP2D4 and CYP3A2. Therefore, caution is needed when HEI is co-administered with drugs metabolized by human CYP2D6 or CYP3A4 in clinic, which may result in increased concentrations of these drugs and relevant herb–drug interactions.

The effects of salvianolic acid B from radix salvia miltiorrhizae on the oral pharmacokinetics of metoprolol and metoprolol acid in rats

The present study aimed to investigate the effects of salvianolic acid B (SalB) isolated from Radix Salvia miltiorrhizae on the oral pharmacokinetics of metoprolol (MET) and metoprolol acid (META) in rats. The pharmacokinetic parameters of MET and META were measured after oral (15 mg/kg) administration of MET in rats in the presence and absence of SalB. Compared to the control given MET alone, with the concurrent administration of SalB (50 mg/kg), the AUC and C(max) of MET increased by 51.7% and 27.7%, and the AUC and C(max) of META decreased by 26.5% and 19.6%, respectively. With the presence of SalB, the metabolic ratio was markedly decreased by 50.8%. However, no significant changes were observed in the pharmacokinetic parameters of SalB when it was combined with MET.

Influence ofCYP2D6*10on the pharmacokinetics of metoprolol in healthy Korean volunteers

Genetic polymorphism of CYP2D6 leads to differences in pharmacokinetics of CYP2D6 substrates. The CYP2D6*10 allele is clinically important in Koreans because of its high frequency in Asians. We investigated whether the pharmacokinetics of metoprolol was altered by the presence of the CYP2D6*10 allele in Korean subjects. One hundred and seven volunteers were recruited and grouped as CYP2D6*1/*1, CYP2D6*1/*10 and CYP2D6*10/*10 according to their genotypes. Metoprolol tartrate 100 mg (Betaloc) was administered orally once to each subject in these three groups (n = 6, 7 and 5, respectively). The pharmacokinetic parameters of metoprolol and its metabolite, alpha-hydroxymetoprolol, and the metabolic ratio for the three groups were estimated and compared. The area under the plasma concentration-time curve (AUC(0-->infinity)), the maximum plasma concentration (C(max)) and the elimination half-life (T(1/2)) of metoprolol and alpha-hydroxymetoprolol for the CYP2D6*10/*10 group were all significantly different from those of the CYP2D6*1/*1 group (P < 0.05). The AUC(0-->infinity)s of metoprolol were 443.7 +/- 168.1, 995.6 +/- 321.4 and 2545.3 +/- 632.0 ng.h/mL, and the AUC(0-->infinity)s of alpha-hydroxymetoprolol were 1232.0 +/- 311.2, 1344.0 +/- 288.1 and 877.4 +/- 103.4 ng.h/mL for groups CYP2D6*1/*1, *1/*10 and *10/*10, respectively. The corresponding T(1/2) values of metoprolol were 2.7 +/- 0.5, 3.2 +/- 1.3 and 5.0 +/- 1.1 h, while those of alpha-hydroxymetoprolol were 5.4+/-1.5, 6.0 +/- 1.4 and 10.5 +/- 4.2 h, respectively. The metabolic ratios of the three groups were significantly different (P < 0.05). The CYP2D6*10 allele altered the pharmacokinetics of metoprolol in Korean subjects and is likely to affect other drugs metabolized by the CYP2D6 enzyme, similarly.

Nonlinear mixed effects model analysis of the pharmacokinetics of metoprolol in middle-aged and elderly Japanese patients

Purpose This study was performed to characterize the factors involved in the pharmacokinetic variability of routinely administered metoprolol in middle-aged and elderly Japanese patients. Methods The 65 whole blood concentration data after repetitive administration to 34 patients were analyzed using the nonlinear mixed effects model (NONMEM) program. A one-compartment model with rapid absorption was parameterized in terms of oral clearance (CL/F) and apparent volume of distribution. We investigated the effect of polymorphic alleles of cytochrome P450 (CYP2D6*2, CYP2D6*10, CYP2C19*2 and CYP2C19*3), age, gender, and heart failure on the pharmacokinetic parameters of metoprolol. Results The CL/F was 64% decreased in the patients homozygous for the CYP2D6*10/*10, as compared with the patients with the CYP2D6*1/*1 or *1/*2 genotype. In addition, the CL/F value in the older (> 70-year-old) patients was 26% lower than that in the younger (<70-year-old) patients. On the other hand, the genotype of CYP2C19, gender, and heart failure showed no significant effect on the pharmacokinetic parameters of metoprolol. Conclusion These findings suggested that a lower dose of metoprolol may be used in the elderly Japanese patients with the CYP2D6*10 allele. Clinical Pharmacology & Therapeutics (2004) 75, P32–P32; doi: 10.1016/j.clpt.2003.11.122