No influence of CYP2D6*10 genotype and phenotype on the pharmacokinetics of nebivolol in healthy Chinese subjects

Clinical pharmacokinetics of nebivolol: a systematic review

Nebivolol is a beta-1 receptor blocker used to treat hypertension, heart failure, erectile dysfunction, vascular disease, and diabetes mellitus. This review investigated the data regarding pharmacokinetic (PK) parameters, drug-drug interactions, dextrorotatory (D), and levorotatory (L) stereoisomers of nebivolol. The articles related to the PK of nebivolol were retrieved by searching the five databases; Google Scholar, PubMed, Cochrane Library, ScienceDirect, and EBSCO. A total of 20 studies comprising plasma concentration-time profile data following the nebivolol's oral and intravenous (IV) administration were included. The area under the concentration-time curve from zero to infinity (AUC0-∞) was 15 times greater in poor metabolizers (PMs) than in extensive metabolizers (EMs). In hypertensive patients, L-nebivolol expressed a higher maximum plasma concentration (Cmax) than D-nebivolol, i.e. 2.5 ng/ml vs 1.2 ng/ml. The AUC0-∞ of nebivolol was 3-fold greater in chronic kidney disease (CKD). The clearance (CL) was increased in obese than in controls from 51.6 ± 11.6 L/h to 71.6 ± 17.4 L/h when 0.5 mg/ml IV solution was infused. Nebivolol showed higher Cmax, AUC0-∞ and half-life (t1/2) when co-administered with bupropion, duloxetine, fluvoxamine, paroxetine, lansoprazole, and fluoxetine. This concise review of nebivolol would be advantageous in assessing all PK parameters, which may be crucial for clinicians to avoid drug-drug interactions, prevent adverse drug events and optimize the dosage regimen in diseased patients diagnosed with hypertension and cardiovascular disorders.

Diltiazem efficacy and CYP2D6 gene polymorphism in patients with atrial fibrillation with rapid ventricular response

BACKGROUND

Diltiazem stands out as one of the front-line drugs administered in the emergency department to achieve acute rate control in patients suffering from atrial fibrillation with rapid Ventricular Response. One of the cytochrome enzymes involved in the metabolism of diltiazem is cytochrome P450 2D6 (CYP2D6). Interindividual differences can act on drug metabolism and thus drug efficacy due to the genetic polymorphism induced by the CYP2D6 enzyme. This study explores the association between the efficacy of diltiazem and the genetic polymorphism of CYP2D6 in patients with atrial fibrillation with rapid ventricular response.

RESULTS

87 out of 93 individuals with ventricular rate > 120 beats/min constituted the patient cohort. The patients were administered 0.25 mg/kg diltiazem intravenously. As a second dose, 0.35 mg/kg diltiazem was administered to patients who reportedly did not receive adequate drug efficacy. Heart rate control was considered to be achieved in patients whose heart rate fell below 110 beats/min and did not rise above 110 beats/min for 2 h. CYP2D6 *2, *3, *4 and *10 represent allele variants and *1 represents wild type (wt) allele. Achieving rate control after one or two doses of diltiazem in normal allele (wt/wt) carriers proved significantly higher than wt/*2, wt/*4 and wt/*10 heterozygous variant carriers. No significant difference was noted in wt/*3 heterozygous variant carriers.

CONCLUSION

The presence of *2, *4 and *10 alleles was observed to significantly compromise the drug efficacy. *3 allele was found to bear no relation to the effect of diltiazem on achieving rate control.

New Data for Nebivolol after In Silico PK Study: Focus on Young Patients and Dosage Regimen

Nebivolol (NEB) is a highly selective β1 receptor antagonist with a distinct pharmacological profile. This drug is approved for the treatment of hypertension in the US, and hypertension and heart failure in Europe. Here, we review observations based on age dependence and explore new drug regimens with in-silico studies, to achieve better efficacy and safety. The clinical data were obtained from six published literature reports. Then the data were used for model building, evaluation, and simulation. A two-compartment model with first-order absorption, lag time, linear elimination, and the following covariates: age and genotype were the ones best describing our population. Simulation of different dose regimens resulted in an increase chance of efficacy and safety when the dose regimen was altered to 6 mg every 36 h. It is worth noting that our population in this study constituted of young and healthy individuals. Studies regarding the effects of NEB according to age are scarce; however, they are needed to further improve efficacy and safety, and reduce adverse effects.

Extracorporeal treatment for poisoning to beta-adrenergic antagonists: systematic review and recommendations from the EXTRIP workgroup

BACKGROUND

β-adrenergic antagonists (BAAs) are used to treat cardiovascular disease such as ischemic heart disease, congestive heart failure, dysrhythmias, and hypertension. Poisoning from BAAs can lead to severe morbidity and mortality. We aimed to determine the utility of extracorporeal treatments (ECTRs) in BAAs poisoning.

METHODS

We conducted systematic reviews of the literature, screened studies, extracted data, and summarized findings following published EXTRIP methods.

RESULTS

A total of 76 studies (4 in vitro and 2 animal experiments, 1 pharmacokinetic simulation study, 37 pharmacokinetic studies on patients with end-stage kidney disease, and 32 case reports or case series) met inclusion criteria. Toxicokinetic or pharmacokinetic data were available on 334 patients (including 73 for atenolol, 54 for propranolol, and 17 for sotalol). For intermittent hemodialysis, atenolol, nadolol, practolol, and sotalol were assessed as dialyzable; acebutolol, bisoprolol, and metipranolol were assessed as moderately dialyzable; metoprolol and talinolol were considered slightly dialyzable; and betaxolol, carvedilol, labetalol, mepindolol, propranolol, and timolol were considered not dialyzable. Data were available for clinical analysis on 37 BAA poisoned patients (including 9 patients for atenolol, 9 for propranolol, and 9 for sotalol), and no reliable comparison between the ECTR cohort and historical controls treated with standard care alone could be performed. The EXTRIP workgroup recommends against using ECTR for patients severely poisoned with propranolol (strong recommendation, very low quality evidence). The workgroup offered no recommendation for ECTR in patients severely poisoned with atenolol or sotalol because of apparent balance of risks and benefits, except for impaired kidney function in which ECTR is suggested (weak recommendation, very low quality of evidence). Indications for ECTR in patients with impaired kidney function include refractory bradycardia and hypotension for atenolol or sotalol poisoning, and recurrent torsade de pointes for sotalol. Although other BAAs were considered dialyzable, clinical data were too limited to develop recommendations.

CONCLUSIONS

BAAs have different properties affecting their removal by ECTR. The EXTRIP workgroup assessed propranolol as non-dialyzable. Atenolol and sotalol were assessed as dialyzable in patients with kidney impairment, and the workgroup suggests ECTR in patients severely poisoned with these drugs when aforementioned indications are present.

Effects of UGT1A1, CYP3A5 and ABCB1 Genetic Variants on Pharmacokinetics of Antihistamine Drug Mizolastine in Chinese Healthy Volunteers

Mizolastine is a selective histamine H1 receptor antagonist for chronic urticaria or allergic rhinitis. We investigated whether the variant genotypes of metabolic enzymes UGT1A1, CYP3A5 and transporter ABCB1 influence pharmacokinetic phenotype of substrate mizolastine in Chinese volunteers. Genotyping of single nucleotide polymorphisms in UGT1A1*6 (G211A), CYP3A5*3 (A6986G) and ABCB1 (C3435T) was determined by the pyrosequencing method. After a single oral dose of 10 mg mizolastine, the plasma concentrations were measured using validated high-performance liquid chromatography in 24 Chinese healthy volunteers. The results showed that the distributions of wild-type homozygotes and variant allele carriers (the sum of variant heterozygotes and variant homozygotes) were as follows: 17 cases (70.8%) versus seven cases (29.2%) in UGT1A1*6 genotypes, five cases (20.8%) versus 19 cases (79.2%) in CYP3A5*3 genotypes and seven cases (29.2%) versus 17 cases (70.8%) in ABCB1 3435T genotypes, respectively. There were no significant differences in pharmacokinetic parameters of mizolastine between the variant allele UGT1A1*6, CYP3A5*3 and ABCB1 3435T carriers and the wild-type homozygotes, and the ratios were as follows: C_max was 101.03%, 86.02% and 105.78%; T_max was 162.35%, 98.98% and 144.90%; AUC_0-28 was 113.04%, 77.35% and 112.71%; and t_1/2 was 95.77%, 72.40% and 100.97%, respectively. In conclusion, these results suggested that the UGT1A1, CYP3A5 and ABCB1 genetic polymorphisms might be not contributed to the interindividual variation of mizolastine pharmacokinetic phenotype in the Chinese population.

Functional characterization of CYP2C19 variants in nebivolol 4-hydroxlation in vitro

Cytochrome P450 2C19 (CYP2C19) allelic variants are thought to play an important part in inter-individual variability in drug metabolism. We evaluated the in vitro hydroxylation of nebivolol by 31 CYP2C19 alleles identified in a Chinese Han population recently. Wild-type CYP2C19*1B and 30 isoforms were highly expressed in insect cells, and the enzymatic activities of CYP2C19 variants towards nebivolol hydroxylation were characterized. Among the 30 CYP2C19 alleles, most of the recombinant CYP2C19 variants exhibited no or significantly low activity compared with CYP2C19*1B. Three variants, CYP2C19*29 (K28I), L16F, and CYP2C19*23 (G91R), showed increased intrinsic clearance of >140% CYP2C19*1B. Combined with a previous study on the effects of CYP2D6 variants on nebivolol metabolism, our comprehensive analyses on the enzymatic activities of CYP2C19 variants towards nebivolol in the present study may contribute to determination of the optimal doses of nebivolol for the treatment of hypertension and understanding of "individualized" medication.

Functional characterization of CYP2D6 novel allelic variants identified in the Chinese Han population

AIM

This study was aimed to functionally characterize four novel CYP2D6 alleles identified in Chinese Han population.

MATERIALS & METHODS

CYP2D6 proteins of wild-type and the four novel variants along with CYP2D6.2 and CYP2D6.10 were heterologously expressed in yeast cells and the kinetic parameters were determined.

RESULTS

Compared with CYP2D6.1 (frequency in Chinese 24.65%), CYP2D6.X (1.63%), CYP2D6.Y (1.50%), CYP2D6.Z (0.81%), CYP2D6.10 (52.53%) and CYP2D6.75 (0.13%) exhibited low activity at different degrees, whereas the kinetic parameters of CYP2D6.2 (11.06%) were much the same with CYP2D6.1. The novel allele CYP2D6.75 showed decreased enzyme activity.

CONCLUSION

This is the first study to conduct functional analysis of CYP2D6 four novel alleles in Chinese Han population, which might be helpful for optimizing pharmacotherapy and the design of personalized medicine.