High prevalence of CYP2D6*41 (G2988A) allele in Saudi Arabians

The Frequency of CYP2D6 and CYP3A4/5 Genotypes and The Impact of Their Allele Translation and Phenoconversion-Predicted Enzyme Activity on Risperidone Pharmacokinetics in Saudi Children with Autism

Data on the role of CYP2D6 and CYP3A4/5 polymorphisms in relation to risperidone (RIS) pharmacokinetics (PK) in children are relatively limited and inconsistent. This is partially attributable to the limited coverage of CYP2D6 and CYP3A4/5 metabolizer phenotypes, particularly those of poor and ultrarapid metabolizers (PMs and UMs), which has led to calls for studies of populations with a non-European background that may carry variants that are less frequent in Europeans. Children ≤ 18 years old with at least 8 weeks of a RIS-based regimen were recruited from three autism centers in Riyadh, Saudi Arabia. The primary outcomes measured were plasma concentrations of RIS and 9-hydroxyrisperidone (9-OH-RIS) and their dose-adjusted (C/D) ratios as a function of phenotypes and activity score (AS). For accurate DNA genotyping, targeted pharmacogenomic testing with the Axiom PharmacoFocus Array was performed via examination of a broad collection of probesets targeting CYP2D6 and CYP3A4/5 variants. The frequency of genotypes/phenotypes and the impact of their allele translation and phenoconversion-predicted enzyme activity were examined. The final cohort included 83 individuals. The most common CYP2D6 phenotype in our population was normal metabolizers (NMs, 66.3%). Inconsistent with some previous studies, the three phenotypes of intermediate metabolizers (IMs), NMs, and UMs were significantly different in terms of RIS concentration, the RIS/9-OH-RIS ratio, the RIS C/D ratio and the 9-OH-RIS C/D ratio. According to AS analyses, there were statistically significant differences in the RIS concentration (P = 0.013), RIS/9-OH-RIS ratio (P < 0.001) and RIS C/D ratio (P = 0.030) when patients were categorized into AS ≤ 1 vs. AS > 1. None of the CYP3A4/5 star allele translated phenotypes revealed a significant influence on any of the RIS PK parameters. Notably, neither CYP2D6 nor CYP3A4/5 phenotyping demonstrated a significant impact on the total active moiety, suggesting that other gene variants could modulate RIS PK. The study confirmed the previously reported partial impact of the CYP2D6 gene on RIS PK. However, future studies using contemporary genotyping techniques targeting a wide range of variants in other candidate genes must be conducted to further examine their interactive effects on RIS PK and the clinical response.

Exploratory focused pharmacogenetic testing reveals novel markers associated with risperidone pharmacokinetics in Saudi children with autism

Background: Autism spectrum disorders (ASDs) encompass a broad range of phenotypes characterized by diverse neurological alterations. Genomic studies have revealed considerable overlap between the molecular mechanisms implicated in the etiology of ASD and genes involved in the pharmacokinetic (PK) and pharmacodynamic (PD) pathways of antipsychotic drugs employed in ASD management. Given the conflicting data originating from candidate PK or PD gene association studies in diverse ethnogeographic ASD populations, dosage individualization based on "actionable" pharmacogenetic (PGx) markers has limited application in clinical practice. Additionally, off-label use of different antipsychotics is an ongoing practice, which is justified given the shortage of approved cures, despite the lack of satisfactory evidence for its safety according to precision medicine. This exploratory study aimed to identify PGx markers predictive of risperidone (RIS) exposure in autistic Saudi children. Methods: This prospective cohort study enrolled 89 Saudi children with ASD treated with RIS-based antipsychotic therapy. Plasma levels of RIS and 9-OH-RIS were measured using a liquid chromatography-tandem mass spectrometry system. To enable focused exploratory testing, genotyping was performed with the Axiom PharmacoFocus Array, which included a collection of probe sets targeting PK/PD genes. A total of 720 PGx markers were included in the association analysis. Results: A total of 27 PGx variants were found to have a prominent impact on various RIS PK parameters; most were not located within the genes involved in the classical RIS PK pathway. Specifically, 8 markers in 7 genes were identified as the PGx markers with the strongest impact on RIS levels (p < 0.01). Four PGx variants in 3 genes were strongly associated with 9-OH-RIS levels, while 5 markers in 5 different genes explained the interindividual variability in the total active moiety. Notably, 6 CYP2D6 variants exhibited strong linkage disequilibrium; however, they significantly influenced only the metabolic ratio and had no considerable effects on the individual estimates of RIS, 9-OH-RIS, or the total active moiety. After correction for multiple testing, rs78998153 in UGT2B17 (which is highly expressed in the brain) remained the most significant PGx marker positively adjusting the metabolic ratio. For the first time, certain human leukocyte antigen (HLA) markers were found to enhance various RIS exposure parameters, which reinforces the gut-brain axis theory of ASD etiology and its suggested inflammatory impacts on drug bioavailability through modulation of the brain, gastrointestinal tract and/or hepatic expression of metabolizing enzymes and transporters. Conclusion: Our hypothesis-generating approach identified a broad spectrum of PGx markers that interactively influence RIS exposure in ASD children, which indicated the need for further validation in population PK modeling studies to define polygenic scores for antipsychotic efficacy and safety, which could facilitate personalized therapeutic decision-making in this complex neurodevelopmental condition.

Mining local exome and HLA data to characterize pharmacogenetic variants in Saudi Arabia

Pharmacogenomics (PGx) is a promising field of precision medicine where efficacy of drugs is maximized while side effects are minimized for individual patients. Knowledge of the frequency of PGx-relevant variants (pharmacovariants) in the local population is a pre-requisite to informed policy making. Unfortunately, such knowledge is largely lacking from the Middle East. Here, we describe the use of a large clinical exome database (n = 13,473) and HLA haplotypes (n = 64,737) from Saudi Arabia, one of the largest countries in the Middle East, along with previously published data from the local population to ascertain allele frequencies of known pharmacovariants. In addition, we queried another exome database (n = 816) of well-phenotyped research subjects from Saudi Arabia to discover novel candidate variants in known PGx genes (pharmacogenes). Although our results show that only 26% (63/242) of class 1A/1B PharmGKB variants were identified, we estimate that 99.57% of the local population have at least one such variant. This translates to a minimum estimated impact of 9% of medications dispensed by our medical center annually. We also highlight the contribution of rare variants where 71% of the pharmacogenes devoid of common pharmacovariants had at least one potentially deleterious rare variant. Thus, we show that approaches that go beyond the use of commercial PGx kits that have been optimized for other populations should be implemented to ensure universal and equitable access of all members of the local population to personalized prescription practices.

The impact of CYP2D6*41 on CYP2D6 enzyme activity using phenotyping methods in urine, plasma, and saliva

Aims: The CYP2D6*41 variant is the second or third frequent reduced function allele in Chinese with a frequency of around 3–4%, while it is the major reduced function allele in Indians, Saudi Arabians and Caucasians with frequencies of around 10–20%. The present study was designed to explore the impact of CYP2D6*41 on the metabolic activity of CYP2D6 using phenotyping methods in urine, plasma, and saliva.

Methods: We used dextromethorphan as the probe drug to analyze the phenotypes of 87 subjects with CYP2D6*1/*1 (n = 22), CYP2D6*1/*2 (n = 33), CYP2D6*2/*2 (n = 4), CYP2D6*1/*41 (n = 5), CYP2D6*2/*41 (n = 3), CYP2D6*10/*41 (n = 16), and CYP2D6*5/*41 (n = 4) for CYP2D6. The ratio of parent drug to metabolite in 3 h saliva, 3 h plasma, and in 0–3 h urine was considered the metabolic ratio (MR).

Results: The CYP2D6*41 allele had substantial impact on the metabolic activity of CYP2D6 regardless of the urinary, plasma, or salivary phenotyping method used. In subjects with CYP2D6*1(or *2)/*1(or *2), *1 (or *2)/*41, *10/*41 and *5/*41 (all p < 0.001), the salivary, plasma, or urinary MR value increased. The MRs in saliva, plasma, and urine displayed high correlations.

Conclusion: The activity score system or the consensus activity score system, instead of the traditional phenotype classification, could predict the CYP2D6 enzyme activity more accurately. CYP2D6*41 had similar or more impact on the CYP2D6 enzyme activity as compared with CYP2D6*10. Assigning *41 a score of 0.5 and assigning *10 a score of 0.25 according to the consensus AS system should be reconsidered.

Prevalence of exposure to pharmacogenetic drugs by the Saudis treated at the health care centers of the Ministry of National Guard

Background

The drugs impacted by genetic variants are known as pharmacogenetic (PGx) drugs. Patients’ responses to these drugs may vary according to the variability in patients’ genetic makeup. Hence, exploring the pharmacogenes that affect drug treatment is vital to ensure optimal therapy and patients’ safety. This study aimed to describe the usage rate of PGx drugs and the frequency of relevant variants in the Saudi population.

Methodology

Prescription patterns over seven years (2015–2021) for Saudi patients on PGx drugs treated at the Ministry of National Guard-Health Affairs (MNG-HA) were investigated. Only registered drugs in the MNG-HA formulary (n = 78) were included. The patients were subgrouped into four age groups: ≤24, 25–44, 45–64, and ≥65 years. Further subgrouping was made according to gender and drugs’ therapeutic categories following anatomical therapeutic chemical (ATC) classification.

Furthermore, an online searching was carried out to identify the pharmacogenes reported in the literature among healthy Saudis. The search included 45 genes that may affect drug outcomes based on evidence rated by either CPIC (A-B levels) or PharmGKB (1–2 levels).

Results

The screened patients were 1,483,905. Patients on PGx drugs accounted for 46.7% (n = 693,077 patients). The analgesic group was the most prescribed drug category (47%), which included ibuprofen (20.5%), celecoxib (6.3%), tramadol (5.8%), and others. Cardiovascular agents were the second-most utilized drug class (24.4%). Omeprazole was the second most commonly used medication (11.1%) but ranked third as a class (gastroenterology). Females used PGx drugs more frequently than males (53.5% versus 46.5%) and a higher usage rate by patients aged 45–64 years (31.3%) was noted. The cytochrome P450 genes (CYP2C9, CYP2C19, and CYP2D6) were estimated to impact responses of 54.3% (n = 1,156,113) of the used drugs (27.2% are possibly affected by CYP2C9, 12.8% by CYP2C19, and 14.3% by CYP2D6). Thirty-five pharmacogenes that characterize Saudi population and their variants’ allele frequencies were identified from previous reports. This study presents the largest reported number of genes that may affect drug therapies among Saudis.

Conclusion

This study confirmed that a high percentage of Saudi patients use PGx drugs and various genotypes of certain pharmacogenes are inherited by the Saudi population.

Frequencies of CYP2D6 genetic polymorphisms in Arab populations

CYP2D6 is a key drug-metabolizing enzyme implicated in the biotransformation of approximately 25% of currently prescribed drugs. Interindividual and interethnic differences in CYP2D6 enzymatic activity, and hence variability in substrate drug efficacy and safety, are attributed to a highly polymorphic corresponding gene. This study aims at reviewing the frequencies of the most clinically relevant CYP2D6 alleles in the Arabs countries. Articles published before May 2021 that reported CYP2D6 genotype and allelic frequencies in the Arab populations of the Middle East and North Africa (MENA) region were retrieved from PubMed and Google Scholar databases. This review included 15 original articles encompassing 2737 individuals from 11 countries of the 22 members of the League of Arab States. Active CYP2D6 gene duplications reached the highest frequencies of 28.3% and 10.4% in Algeria and Saudi Arabia, respectively, and lowest in Egypt (2.41%) and Palestine (4.9%). Frequencies of the loss-of-function allele CYP2D6*4 ranged from 3.5% in Saudi Arabia to 18.8% in Egypt. The disparity in frequencies of the reduced-function CYP2D6*10 allele was perceptible, with the highest frequency reported in Jordan (14.8%) and the lowest in neighboring Palestine (2%), and in Algeria (0%). The reduced-function allele CYP2D6*41 was more prevalent in the Arabian Peninsula countries; Saudi Arabia (18.4%) and the United Arab Emirates (15.2%), in comparison with the Northern Arab-Levantine Syria (9.7%) and Algeria (8.3%). Our study demonstrates heterogeneity of CYP2D6 alleles among Arab populations. The incongruities of the frequencies of alleles in neighboring countries with similar demographic composition emphasize the necessity for harmonizing criteria of genotype assignment and conducting comprehensive studies on larger MENA Arab populations to determine their CYP2D6 allelic makeup and improve therapeutic outcomes of CYP2D6- metabolized drugs.

Role of P34S, G169R, R296C, and S486T Substitutions in Ligand Access and Catalysis for Cytochrome P450 2D6 Allelic Variants CYP2D6*14A and CYP2D6*14B

BACKGROUND

Genetic polymorphism of cytochrome P450 (CYP) contributes to variability in drug metabolism, clearance, and response. This study aimed to investigate the functional and molecular basis for altered ligand binding and catalysis in CYP2D6*14A and CYP2D6*14B, two unique alleles common in the Asian population.

METHODS

CYP proteins expressed in Escherichia coli were studied using the substrate 3-cyano-7- ethoxycoumarin (CEC) and inhibitor probes (quinidine, fluoxetine, paroxetine, terbinafine) in the enzyme assay. Computer modelling was additionally used to create three-dimensional structures of the CYP2D6*14 variants.

RESULTS

Kinetics data indicated significantly reduced intrinsic clearance in CYP2D6*14 variants, suggesting that P34S, G169R, R296C, and S486T substitutions worked cooperatively to alter the conformation of the active site that negatively impacted the deethylase activity of CYP2D6. For the inhibition studies, IC50 values decreased in quinidine, paroxetine, and terbinafine but increased in fluoxetine, suggesting a varied ligand-specific susceptibility to inhibition. Molecular docking further demonstrated the role of P34S and R296C in altering access channel dimensions, thereby affecting ligand access and binding and subsequently resulting in varied inhibition potencies.

CONCLUSION

In summary, the differential selectivity of CYP2D6*14 variants for the ligands (substrate and inhibitor) was governed by the alteration of the active site and access channel architecture induced by the natural mutations found in the alleles.

Genetic variability of CYP2D6, CYP3A4 and CYP3A5 among the Egyptian population

Aim: This study investigated major allelic variants of CYP2D6, CYP3A4 and CYP3A5 in Egyptians, an Arabic population for which there is little information regarding these important pharmacogenes. Patients & methods: CYP2D6*2, *4, *5, *10, *41 and gene copy number variation, as well as CYP3A4*22 and CYP3A5*3 were determined with commercially available TaqMan assays in 145 healthy study participants. Results: The CYP2D6 alleles identified suggest that the prevalence of poor metabolizers is low as none were found among the 145 subjects investigated. The frequency for CYP3A5 nonexpressers was 74.5% and the CYP3A4*22 allele frequency was low at 2.0%. Conclusion: These preliminary findings indicate that pharmacogene variation in Egyptians is different from those of other Middle Eastern/Arabic populations and warrants further investigation.

Relative addictive potential of opioid analgesic agents

Opioid overdoses and deaths continue to be a problem in the USA with a significant portion related to prescribed opioid analgesic agents. The role of pharmacogentic factors in opioid addiction is an active area of research. While all opioid analgesic agents have some addictive potential, it is clear that there are some with greater addictive potential. Oxycodone is the most widely abused opioid analgesic and it appears to predispose to chronic use with high likability by users. Fentanyl and hydromorphone are both very lipophilic allowing rapid penetration into the CNS, but are not rated as highly as other agents. Providers should consider the risk of addiction with the opioids they prescribe and give those with a lower addictive potential.

Predicting steady-state endoxifen plasma concentrations in breast cancer patients by CYP2D6 genotyping or phenotyping. Which approach is more reliable?

In previous studies, steady-state Z-endoxifen plasma concentrations (ENDOss) correlated with relapse-free survival in women on tamoxifen (TAM) treatment for breast cancer. ENDOss also correlated significantly with CYP2D6 genotype (activity score) and CYP2D6 phenotype (dextromethorphan test). Our aim was to ascertain which method for assessing CYP2D6 activity is more reliable in predicting ENDOss. The study concerned 203 Caucasian women on tamoxifen-adjuvant therapy (20 mg q.d.). Before starting treatment, CYP2D6 was genotyped (and activity scores computed), and the urinary log(dextromethorphan/dextrorphan) ratio [log(DM/DX)] was calculated after 15 mg of oral dextromethorphan. Plasma concentrations of TAM, N-desmethyl-tamoxifen (ND-TAM), Z-4OH-tamoxifen (4OH-TAM) and ENDO were assayed 1, 4, and 8 months after first administering TAM. Multivariable regression analysis was used to identify the clinical and laboratory variables predicting log-transformed ENDOss (log-ENDOss). Genotype-derived CYP2D6 phenotypes (PM, IM, NM, EM) and log(DM/DX) correlated independently with log-ENDOss. Genotype-phenotype concordance was almost complete only for poor metabolizers, whereas it emerged that 34% of intermediate, normal, and ultrarapid metabolizers were classified differently based on log(DM/DX). Multivariable regression analysis selected log(DM/DX) as the best predictor, with patients' age, weak inhibitor use, and CYP2D6 phenotype decreasingly important: log-ENDOss = 0.162 - log(DM/DX) × 0.170 + age × 0.0063 - weak inhibitor use × 0.250 + IM × 0.105 + (NM + UM) × 0.210; (R2  = 0.51). In conclusion, log(DM/DX) seems superior to genotype-derived CYP2D6 phenotype in predicting ENDOss.

Major CYP450 polymorphism Among Saudi Patients

BACKGROUND

Cytochrome P450 (CYP) contributes to a huge collection of medicinal products' Phase I metabolization. We aimed to summarize and investigate the current evidence regarding the frequency of CYP2D6, CYP2C9, CYP2C19, MDR1 in Saudi Arabia.

METHODS

A computerized search in four databases was done using the relevant keywords. Screening process was done in two steps; title and abstract screening and full-text screening. Data of demographic and characteristics of included studies and patients was extracted and tabulated.

RESULTS

Ten studies were eligible for our criteria and were included in this systematic review. Age of participants ranged between 17-65 years. Only two subjects showed PM phenotype of CYP2C19 in Saudi population. The most frequent alleles were CYP2C19*1 (62.9%), CYP2C19*2 (11.2%-32%), and CYP2C19*17 (25.7%). The CYP2C19m1 was observed in 97 cases of extensive metabolizing (EM) phenotype CYP2C19. Concerning the CYP2C9, the most frequent alleles were CYP2C9*1 and CYP2C9*2, and the most frequent genotype was CYP2C9*1*1. The CYP2D6*41 allele and C1236T MDR1 were the most frequent allele in this population.

CONCLUSION

The current evidence suggests that Saudi Arabians resembled European in the frequency of CYP2C19, Caucasians in both the incidence of CYP2C9 and CYP2C19m1 and absence of CYP2C19m2. The CYP2D6*41 allele frequency in Saudi Arabians is relatively high. We recommend a further research to evaluate the basic and clinical relevance of gene polymorphism in such ethnicity.

Resequencing CYP2D6 gene in Indian population: CYP2D6*41 identified as the major reduced function allele

Aim: The CYP2D6 gene is highly polymorphic and harbors population specific alleles that define its predominant metabolizer phenotype. This study aimed to identify polymorphisms in Indian population owing to scarcity of CYP2D6 data in this population. Materials & methods: The CYP2D6 gene was resequenced in 105 south Indians using next generation sequencing technology and haplotypes were reconstructed. Results & conclusion: Four novel missense variants have been designated as CYP2D6*110, *111, *112 and *113. The most common alleles were CYP2D6*1 (42%), *2 (32%), and *41 (12.3%) and diplotypes were CYP2D6*1/*2 (26%), *1/*1 (11%), *2/*41 (10%) and *1/*41 (7%) accounting for high incidence of extensive metabolizers in Indians.

Distribution of CYP2D6 polymorphism in the Middle Eastern region

Cytochrome P450 2D6 (CYP2D6) is an important drug-metabolizing enzyme involved in the pharmacokinetic metabolism of drugs. CYP2D6 gene is highly polymorphic, and the combination of its different alleles yields different phenotypes including extensive metabolizer (EM), intermediate metabolizer (IM), poor metabolizer (PM), and ultrarapid metabolizer (UM). Genotyping of the important alleles for this gene in different ethnicities is of particular importance for assessing the efficacy of various drugs. In this study, we reviewed the CYP2D6 allele and phenotype frequencies predicted from the genotypes of CYP2D6 in the Middle East area. Regardless of different ethnicities, the CYP2D6*41 allele frequency was shown to be higher than that of other reduced functional alleles. In addition, CYP2D6*4 was the most frequent nonfunctional allele in all studied populations in the Middle East. Taken together, our findings illustrated that the frequencies of PM or IM alleles and different genotypes harboring these alleles are relatively high in the Middle Eastern countries. Therefore, the study of CYP2D6 alleles for each patient to detect those that are at risk is of great importance to prevent adverse drug reactions through individualization therapy.

Single nucleotide and structural variants of CYP2D6 gene in Kinh Vietnamese population

CYP2D6 genetic variations could result in alteration of CYP2D6 enzyme activity, leading to dissimilarity among individuals in regard of drug metabolism.This study aims to detect all genetic variants, allele, and genotype frequencies of CYP2D6 gene in 136 unrelated healthy Kinh Vietnamese volunteers. All single nucleotide variants (SNVs) and structural variations (SVs) of CYP2D6 gene were identified by Sanger sequencing and multiplex ligation-dependent probe amplification (MLPA) assay.Totally, 30 SNVs and 9 SVs including a whole gene deletion, 8 hybrid structures, and tandem arrangements were identified. Of the 7 novel SNVs detected, the 3157G>T (R329L) substitution was predicted to be deleterious by PROVEAN; the 3851G>A (W358X) variant resulted in a truncated protein; and the 2988G>A variant located in the intron 6 was predicted to be capable of modifying splicing motif by Human Splicing Finder. We determined 29 different genotypes of CYP2D6 from 136 individuals. The most common alleles were the CYP2D6*10 (43.75%), *1 (18.75%), and tandem arrangement *36-*10 (12.13%).This study provides best information on CYP2D6 polymorphism comprising the newly discovered SNVs, structural variations, and their frequencies in Kinh Vietnamese. These new data would be valuable in view of precise dosing of CYP2D6 metabolized drugs and giving better treatment outcome.

Evaluating the impact of missenses mutations in CYP2D6*7 and CYP2D6*14A: does it compromise tamoxifen metabolism?

CYP2D6 is a high polymorphic enzyme from P450, responsible for metabolizing almost 25% of drugs. The distribution of different mutations among CYP2D6 alleles has been associated with poor, intermediate, extensive and ultra-metabolizers.

AIM

To evaluate how missenses mutations in CYP2D6*7 and CYP2D6*14A poor metabolizer alleles affect CYP2D6 stability and function.

MATERIALS & METHODS

CYPalleles database was used to collect polymorphisms data present in 105 alleles. We selected only poor metabolizers alleles that presented exclusively missenses mutations. They were analyzed through seven algorithms to predict the impact on CYP2D6 structure and function.

RESULTS

H324P, the unique mutation in CYP2D6*7, has high impact in enzyme function due to its occurrence between two alpha-helixes involved in active site dynamics. G169R, a mutation that occurs only in CYP2D6*14A, leads to the gain of solvent accessibility and severe protein destabilization.

CONCLUSION

Our in silico analysis showed that missenses mutations in CYP2D6*7 and CYP2D6*14A cause CYP2D6 dysfunction.

Influence of CYP2D6 and β2-adrenergic receptor gene polymorphisms on the hemodynamic response to propranolol in Chinese Han patients with cirrhosis

BACKGROUND AND AIM

Propranolol is widely used to prevent gastroesophageal variceal bleeding; however, some patients could not benefit from propranolol. This study is to evaluate the relationship between CYP2D6 and β2-adrenergic receptor (β2-AR) gene polymorphisms and the hemodynamic response to propranolol in Chinese Han patients.

METHODS

The clinical data of patients with gastroesophageal varices undergoing hepatic venous pressure gradient (HVPG) measurement before and 7 days after oral propranolol administration in our department were collected. Four single nucleotide polymorphisms of CYP2D6 and β2-AR genes were detected. The relationship was identified by logistic regression model.

RESULTS

Thirty patients were involved in the analysis. Sixty milligram propranolol twice each day was well tolerated by all the patients. The initial and secondary average of HVPG was 17.4 ± 5.8 mmHg vs. 13.2 ± 4.8 mmHg, respectively (t = 5.726, P < 0.001). Twenty patients responded to propranolol. The mean reduction value of HVPG was 6.6 ± 3.6 mmHg (range from 3 to 19). Genotype analysis showed: 20 homozygotes for C/C188 and 10 for heterozygous C/T188, 8 homozygotes for G/G4268 and 22 heterozygotes for G/C4268, 14 homozygotes for Gly16 and 10 heterozygotes, and 6 homozygotes for Arg16, 27 homozygotes for Gln27 and 3 heterozygotes. The multivariate logistic regression analysis indicated that CYP2D6 (188C>T) genotype was an independent predicting factor for HVPG response to propranolol (P = 0.033).

CONCLUSIONS

CYP2D6 (188C>T) gene polymorphisms influence the hemodynamic response to propranolol in this population of Chinese Han patients with gastroesophageal varices. However, HVPG response cannot be completely predicted from CYP2D6 and β2-AR gene polymorphisms.

CYP2D6 allele distribution in Macedonians, Albanians and Romanies in the Republic of Macedonia

Cytochrome P450 2D6 (CYP2D6) is an enzyme of great importance for the metabolism of clinically used drugs. More than 100 variants of the CYP2D6 gene have been identified so far. The aim of this study was to investigate the allele distribution of CYP2D6 gene variants in 100 individuals of each of the Macedonian, Albanian and Romany population, by genotyping using long range polymerase chain reaction (PCR) and a multiplex single base extension method. The most frequent variants and almost equally distributed in the three groups were the fully functional alleles *1 and *2. The most common non functional allele in all groups was *4 that was found in 22.5% of the Albanians. The most common allele with decreased activity was *41 which was found in 23.0% of the Romany ethnic group, in 11.0% of the Macedonians and in 10.5% of the Albanians. Seven percent of the Albanians, 6.0% of the Romani and 4.0% of the Macedonians were poor metabolizers, while 5.0% of the Macedonians, 1.0% of Albanians and 1.0% of the Romanies were ultrarapid metabolizers. We concluded that the CYP2D6 gene locus is highly heterogeneous in these groups and that the prevalence of the CYP2D6 allele variants and genotypes in the Republic of Macedonia is in accordance with that of other European populations.