Modeled Hepatic/Plasma Exposures of Fluvastatin Prescribed Alone in Subjects with Impaired Cytochrome P450 2C9*3 as One of Possible Determinant Factors Likely Associated with Hepatic Toxicity Reported in a Japanese Adverse Event Database

Fluvastatin is a 3-hydroxy-3-methylglutaryl CoA reductase inhibitor that competitively inhibits human cytochrome P450 (P450) 2C9 in vitro. Drug interactions between a variety of P450 2C9 substrates/inhibitors and fluvastatin can increase the incidence of fluvastatin-related hepatic or skeletal muscle toxicity in vivo. In this survey, the prescribed dosage of fluvastatin was reduced or discontinued in 133 of 164 patients receiving fluvastatin alone, as recorded in the Japanese Adverse Drug Event Report database of spontaneously reported events. The median days to onset of fluvastatin-related disorders were in the range 30-35 d in the 87 patients. Therefore, we aimed to focus on fluvastatin and, using the pharmacokinetic modeling technique, estimated the virtual plasma and hepatic exposures in subjects harboring the impaired CYP2C9*3 allele. The plasma concentrations of fluvastatin modeled after a virtual oral 20-mg dose increased in homozygotes with CYP2C9*3; the area under the plasma concentration curve was 4.9-fold higher than that in Japanese homozygotes for wild-type CYP2C9*1. The modeled hepatic concentrations of fluvastatin in patients with CYP2C9*3/*3 after virtual daily 20-mg doses for 7 d were 31-fold higher than those in subjects with CYP2C9*1/*1. However, heterozygous Chinese patients with CYP2C9*1/*3 reportedly have a limited elevation (1.2-fold) in plasma maximum concentrations. Virtual hepatic/plasma exposures in subjects harboring the impaired CYP2C9*3 allele estimated using pharmacokinetic modeling indicate that such exposure could be a causal factor for hepatic disorders induced by fluvastatin prescribed alone in a manner similar to that for interactions with a variety of co-administered drugs.

Genetic Determinants of Response to Statins in Cardiovascular Diseases

Despite extensive efforts to identify patients with cardiovascular disease (CVD) who could most benefit from the treatment approach, patients vary in their benefit from therapy and propensity for adverse drug events. Genetic variability in individual responses to drugs (pharmacogenetics) is considered an essential determinant in responding to a drug. Thus, understanding these pharmacogenomic relationships has led to a substantial focus on mechanisms of disease and drug response. In turn, understanding the genomic and molecular bases of variables that might be involved in drug response is the main step in personalized medicine. There is a growing body of data evaluating drug-gene interactions in recent years, some of which have led to FDA recommendations and detection of markers to predict drug responses (e.g., genetic variant in VKORC1 and CYP2C9 genes for prediction of drug response in warfarin treatment). Also, statins are widely prescribed drugs for the prevention of CVD. Atorvastatin, fluvastatin, rosuvastatin, simvastatin, and lovastatin are the most common statins used to manage dyslipidemia. This review provides an overview of the current knowledge on the pharmacogenetics of statins, which are being used to treat cardiovascular diseases.

Potential Pharmacokinetic Interactions of Common Cardiovascular Drugs and Selected European and Latin American Herbal Medicines: A Scoping Review

BACKGROUND

Herb-drug interactions are nowadays an important decision factor in many healthcare interventions. Patients with cardiovascular risk factors such as hyperlipidemia and hypertension are usually prescribed long-term treatments. We need more informed decision tools to direct future clinical research and decision making to avoid HDI occurrences in this group.

METHODS

A scoping review was conducted using data from online databases such as PUBMED, the National Library of Medicine, and the electronic Medicines Compendium. Included studies consisted of the reported effects on Phase 1/2 and P-glycoprotein of herbal medicines listed in the medicines agencies of Latin America and Europe and drugs used for cardiovascular conditions (statins, diuretics, beta blockers, calcium channel blockers, and ACE inhibitors). The cross tabulation of the results allowed for finding potential HDI.

RESULTS AND CONCLUSIONS

as per the preclinical data reviewed here, we encourage more clinical research on whether drugs with apparently very low interaction risk, such as pravastatin, nadolol, and nimodipine/nitrendipine, may help prevent HDI when statins, beta blockers, and calcium channel blockers, respectively, are prescribed for long-term treatments.

Study of the allelic variants CYP2C9*2 and CYP2C9*3 in samples of the Peruvian mestizo population

Introducción.

El citocromo CYP2C9 metaboliza, aproximadamente, el 15 % de los fármacos prescritos. Su gen presenta alelos cuyas frecuencias difieren entre grupos étnicos y poblaciones. Los alelos CYP2C9*2 y CYP2C9*3 dan cuenta de una enzima con actividad disminuida cuya frecuencia no ha sido determinada en la población mestiza peruana.

Objetivo.

Caracterizar la frecuencia de las variantes *2 (rs1799853) y *3 (rs1057910) del gen CYP2C9 en muestras de población mestiza peruana provenientes de Lima, Tacna y Junín.

Materiales y métodos.

Se hizo un estudio descriptivo, observacional y prospectivo, con muestreo no probabilístico, por conveniencia e incidental. Se incluyeron 218 sujetos según los criterios de inclusión y exclusión; todos los participantes otorgaron su consentimiento informado. El ADN genómico se obtuvo mediante hisopado de mucosa oral, y la detección de los genotipos para los alelos CYP2C9*2 y CYP2C9*3 se hizo mediante reacción en cadena de la polimerasa (PCR) en tiempo real, utilizando sondas TaqMan™.

Resultados.

Las variantes de CYP2C9*2 y CYP2C9*3 están presentes en la población mestiza peruana con frecuencias de 0,046 y 0,062, respectivamente. El análisis de las frecuencias genotípicas observadas permitió predecir que la frecuencia de fenotipos metabolismo intermedio sería del 15,13 % (CYP2C9*1/*2: 5,96 %; CYP2C9*1/*3: 9,17 %), y la de fenotipos de metabolismo lento, del 3,22 % (CYP2C9*2/*2: 1,38 %; CYP2C9*3/*3: 1,38 %; CYP2C9*2/*3: 0,46 %).

Conclusiones.

Se lograron determinar las frecuencias genotípicas y alélicas para las variantes *2 y *3 del gen CYP2C9 en una muestra no probabilística de población mestiza peruana. Las frecuencias obtenidas (0,046 y 0,062, respectivamente) están entre las esperadas para una población mestiza sudamericana con ascendencia amerindia, europea, africana y asiática.

Effects of Baoyuan decoction, a traditional Chinese medicine formula, on the activities and mRNA expression of seven CYP isozymes in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Baoyuan decoction (BYD), a traditional Chinese medicine (TCM) formula, is composed of four herbs and widely used with western drugs to treat coronary heart disease, aplastic anemia and chronic renal failure in clinic. However, no study of the effect of BYD on the cytochrome P450 (CYP) activities has been reported.

AIM OF THE STUDY

The purpose of the present study was to evaluate the potential influences of BYD on the activities of seven CYP isozymes (CYP1A2, 2B6, 2C9, 2C19, 2D6, 2E1, and 3A4) in rats.

MATERIALS AND METHODS

A sensitive and selective UPLC-MS/MS method for simultaneous determination of seven probe drugs and internal standard (IS) in rat plasma was developed and validated. The influence of BYD on the activities of CYP isozymes and mRNA expression levels were carried out by comparing plasma pharmacokinetics and real-time reverse transcription-polymerase chain reaction (RT-PCR) of probe drugs between control and BYD treatment groups respectively.

RESULTS

The calibration curve were linear, with correlation coefficient (r) > 0.99 for seven probe drugs. The intra and inter-assay accuracy and precision of the method were within ± 14.9% and the recoveries ranged from 83.2% to 106.1%. Compared with control group, BYD at low (1.46 g/kg) and high (7.30 g/kg) dosages could significantly increase C_max and AUC_0-t of chlorzoxazone and testosterone, while decrease AUC_0-t of phenacetin at high dosage and increase AUC_0-t of tolbu_tamide and metoprolol. Additionally, BYD had increased AUC_0-t of bupropion at low dosage and decreased it at high dosage. The mRNA expression results were in accordance with those of pharmacokinetic.

CONCLUSION

BYD exhibited inhibitory effects on CYP2C9, CYP2E1, and CYP3A4. Moreover, BYD had induction effects on CYP1A2, and CYP2D6 activities. However, no significant change in CYP2C19 activity was observed. It would be useful for the safe and effective usage of BYD in clinic.

Impact of CYP2D6 Functional Allelic Variations on Phenoconversion and Drug-Drug Interactions

We investigated whether CYP2D6 extensive metabolizers carrying a nonfunctional allele are at higher risk of phenoconversion to poor metabolizers in the presence of CYP2D6 inhibitors. Seventeen homozygous carriers of two fully-functional alleles and 17 heterozygous carriers of one fully-functional and one nonfunctional allele participated in this trial. Dextromethorphan 5 mg and tramadol 10 mg were given at each of the three study sessions. CYP2D6 was inhibited by duloxetine 60 mg (session 2) and paroxetine 20 mg (session 3). A higher rate of phenoconversion to intermediate metabolizers with duloxetine (71% vs. 25%, P = 0.009) and to poor metabolizers with paroxetine (94% vs. 56%, P = 0.011) was observed in heterozygous than homozygous extensive metabolizers. The magnitude of drug-drug interaction between dextromethorphan and paroxetine was higher in homozygous than in heterozygous subjects (14.6 vs. 8.5, P < 0.028). Our study suggests that genetic extensive metabolizers may not represent a homogenous population and that available genetic data should be considered when addressing drug-drug interactions in clinical practice.