Polymorphisms and the Pocketbook: The Cost-Effectiveness of Cytochrome P450 2C19 Genotyping in the Eradication ofHelicobacter pyloriInfection Associated with Duodenal Ulcer

Cost Effectiveness of Pharmacogenetic Testing for Drugs with Clinical Pharmacogenetics Implementation Consortium (CPIC) Guidelines: A Systematic Review

The objective of this study was to evaluate the evidence on cost-effectiveness of pharmacogenetic (PGx)-guided treatment for drugs with Clinical Pharmacogenetics Implementation Consortium (CPIC) guidelines. A systematic review was conducted using multiple biomedical literature databases from inception to June 2021. Full articles comparing PGx-guided with nonguided treatment were included for data extraction. Quality of Health Economic Studies (QHES) was used to assess robustness of each study (0-100). Data are reported using descriptive statistics. Of 108 studies evaluating 39 drugs, 77 (71%) showed PGx testing was cost-effective (CE) (N = 48) or cost-saving (CS) (N = 29); 21 (20%) were not CE; 10 (9%) were uncertain. Clopidogrel had the most articles (N = 23), of which 22 demonstrated CE or CS, followed by warfarin (N = 16), of which 7 demonstrated CE or CS. Of 26 studies evaluating human leukocyte antigen (HLA) testing for abacavir (N = 8), allopurinol (N = 10), or carbamazepine/phenytoin (N = 8), 15 demonstrated CE or CS. Nine of 11 antidepressant articles demonstrated CE or CS. The median QHES score reflected high-quality studies (91; range 48-100). Most studies evaluating cost-effectiveness favored PGx testing. Limited data exist on cost-effectiveness of preemptive and multigene testing across disease states.

Cost-Utility Analysis of CYP2C19 Genotype Detection for Selection of Acid-Suppressive Therapy with Lansoprazole or Vonoprazan for Patients with Reflux Esophagitis in China

BACKGROUND

The cytochrome P450 (CYP) 2C19 genotype has a profound effect on the efficacy of lansoprazole, with less of an influence on vonoprazan. Both are first-choice drugs for the treatment of reflux esophagitis in China.

OBJECTIVE

We aimed to estimate the cost-effectiveness of acid-suppressive treatments in Chinese patients with reflux esophagitis over 1 year from the societal perspective.

METHODS

We developed a decision-based Markov model with a 4-week cycle to simulate the economic benefits and quality-adjusted life-years between different treatment strategies for patients with reflux esophagitis: universal lansoprazole, universal vonoprazan, and CYP2C19 genotype-guided strategies. The primary outcome was the incremental cost-effectiveness ratio. Data sources were the published literature, clinical trials, documents, and local charges. We used sensitivity analyses to detect the robustness of the findings and explored subgroup analyses and scenario analyses to make further evaluations.

RESULTS

Compared to lansoprazole, vonoprazan and the CYP2C19 genotype-guided strategy were not preferable for Chinese patients with reflux esophagitis, with an incremental cost-effectiveness ratio of 222,387.1316 yuan/quality-adjusted life-year and 349,627.5000 yuan/quality-adjusted life-year, respectively. Sensitivity analyses showed the impact factors were the utility scores and the expenditures for the maintenance stage with lansoprazole and vonoprazan. When the willingness-to-pay threshold was 215,484 yuan/quality-adjusted life-year, 46.20% of the reflux esophagitis population was willing to pay for vonoprazan, compared with 8.30% for the CYP2C19 genotype-guided strategies. Vonoprazan and the CYP2C19 genotype-guided strategy were cost effective in the severe reflux esophagitis population, and in the reduction of the price of vonoprazan.

CONCLUSIONS

The health economic evaluations revealed that for Chinese patients with reflux esophagitis, vonoprazan and the CYP2C19 genotype-guided strategy were not cost-effective regimens compared with lansoprazole. However, we found that in certain conditions like a reduction in the price of vonoprazan and in patients with severe reflux esophagitis these could be cost-effective.

AmpliChip for Cytochrome P-450 Genotyping: The Epoch of Personalized Prescriptions

The clinical importance of genetic polymorphisms in drug metabolism is well-known in clinical pharmacotherapy. The first widely available pharmacogenomic microarray technology approved by the Food and Drug Administration as a medical device to clinically genotype genetic polymorphisms in drug metabolism is now available with the launch of AmpliChip technology. This readily accessible clinical microarray test allows the genotyping of cytochrome (CYP) P-450 2D6 and 2C19 and marks a milestone in the epoch of evidence based personalized medicine. Many commonly used drugs are substrates for CYP2D6 and CYP 2C19 and hence may potentially demonstrate phenotypic differences as poor, intermediate, extensive, and ultrarapid metabolizers. These phenotypic variations could lead to expressed differences in pharmacotherapeutic patient outcomes. AmpliChip currently allows for testing of multiple alleles (31) in a single assay. Other technologies for pharmacogenomics are on the horizon. This article reviews the importance of polymorphic enzymes and genotyping as to how genetic polymorphisms alter pharmacotherapy and the emergence of a plethora of technologies that may become routinely available for clinical pharmacogenomic testing in the near future.

Economic Evaluations of Pharmacogenetic and Pharmacogenomic Screening Tests: A Systematic Review. Second Update of the Literature

Objective

Due to extended application of pharmacogenetic and pharmacogenomic screening (PGx) tests it is important to assess whether they provide good value for money. This review provides an update of the literature.

Methods

A literature search was performed in PubMed and papers published between August 2010 and September 2014, investigating the cost-effectiveness of PGx screening tests, were included. Papers from 2000 until July 2010 were included via two previous systematic reviews. Studies’ overall quality was assessed with the Quality of Health Economic Studies (QHES) instrument.

Results

We found 38 studies, which combined with the previous 42 studies resulted in a total of 80 included studies. An average QHES score of 76 was found. Since 2010, more studies were funded by pharmaceutical companies. Most recent studies performed cost-utility analysis, univariate and probabilistic sensitivity analyses, and discussed limitations of their economic evaluations. Most studies indicated favorable cost-effectiveness. Majority of evaluations did not provide information regarding the intrinsic value of the PGx test. There were considerable differences in the costs for PGx testing. Reporting of the direction and magnitude of bias on the cost-effectiveness estimates as well as motivation for the chosen economic model and perspective were frequently missing.

Conclusions

Application of PGx tests was mostly found to be a cost-effective or cost-saving strategy. We found that only the minority of recent pharmacoeconomic evaluations assessed the intrinsic value of the PGx tests. There was an increase in the number of studies and in the reporting of quality associated characteristics. To improve future evaluations, scenario analysis including a broad range of PGx tests costs and equal costs of comparator drugs to assess the intrinsic value of the PGx tests, are recommended. In addition, robust clinical evidence regarding PGx tests’ efficacy remains of utmost importance.

Economic Evaluations of Pharmacogenetic Approaches in Infectious Diseases: A Review of Current Approaches and Evaluation of Critical Aspects Affecting their Quality

Pharmacogenetics holds great potential for improving the effectiveness of treatment modalities in infectious diseases by taking into account the genetic determinants of both the host and infectious agents' individuality. Better utilization of resources and improved therapeutic efficiency are the expected outcomes of personalized medicine using pharmacogenetic and pharmacogenomics information made available by technological advances. However, there has been growing concern in the clinical community regarding the evaluation of the true benefits of these approaches. This perception is partly due to the limited number and perceived poor quality of economic evaluations in this field, and initiatives aimed at harmonizing and communicating strategies improving the quality of these studies and their acceptance by the clinical community are greatly needed. This paper reviews current literature of economic evaluations of pharmacogenetics interventions guiding pharmacotherapy in infectious diseases. PubMed and the NHS Centre for Reviews and Dissemination databases were searched using a combination of five broad research terms related to pharmacogenetic approaches, and papers relative to economic evaluations of pharmacogenetic interventions in infectious diseases retained for further analysis. Using these criteria, a total of 14 papers were included in this review. The area of economic evaluation of pharmacogenetic interventions in infectious diseases remains understudied and would benefit from greater harmonization. The main weaknesses of evaluations reviewed in this paper seem to be represented by poor evidence of pharmacogenetic marker validation, inconsistencies in the selection of costs and utility included in the economic models and the choice of sensitivity analysis. All these factors limit the overall transparency of the studies, greater acceptance of their results and applicability to diverse and possibly resourcelimited environments where these approaches could be expected to have the greater impact.

Clinically significant psychotropic drug-drug interactions in the primary care setting

In recent years, the growing numbers of patients seeking care for a wide range of psychiatric illnesses in the primary care setting has resulted in an increase in the number of psychotropic medications prescribed. Along with the increased utilization of psychotropic medications, considerable variability is noted in the prescribing patterns of primary care providers and psychiatrists. Because psychiatric patients also suffer from a number of additional medical comorbidities, the increased utilization of psychotropic medications presents an elevated risk of clinically significant drug interactions in these patients. While life-threatening drug interactions are rare, clinically significant drug interactions impacting drug response or appearance of serious adverse drug reactions have been documented and can impact long-term outcomes. Additionally, the impact of genetic variability on the psychotropic drug's pharmacodynamics and/or pharmacokinetics may further complicate drug therapy. Increased awareness of clinically relevant psychotropic drug interactions can aid clinicians to achieve optimal therapeutic outcomes in patients in the primary care setting.

Development and implementation of a pharmacist-managed clinical pharmacogenetics service

PURPOSE

The development and implementation of a pharmacist-managed clinical pharmacogenetics service are described.

SUMMARY

A pharmacist-managed clinical pharmacogenetics service was designed and implemented at an academic specialty hospital to provide clinical pharmacogenetic testing for gene products important to the pharmacodynamics of medications used in the hospital's patients. A series of accredited educational seminars were conducted for our pharmacists to establish competencies in providing pharmacogenetic consults for the genes to be tested by the clinical pharmacogenetics service. The service was modeled after and integrated with an already-established clinical pharmacokinetics service. A steering committee was formed to evaluate the use of available tests, new evidence for implementation of additional tests, and other service quality metrics. All clinical pharmacogenetic test results are first reported to one of the pharmacists, who reviews the result and provides a written consultation. The consultation includes an interpretation of the result and recommendations for any indicated changes to therapy. In 2009, 136 clinical pharmacogenetic tests were performed. The service has been met with positive clinician feedback. The successful implementation of this service highlights the leadership role that pharmacists can take in moving pharmacogenetics from research to patient care.

CONCLUSION

The development of and experience with a pharmacist-managed clinical pharmacogenetics service are described. The program's success has depended on collaboration between the clinical laboratory and pharmacists, and pharmacists' pharmacogenetic recommendations have been well accepted by prescribers.

Prasugrel vs. clopidogrel for cytochrome P450 2C19-genotyped subgroups: integration of the TRITON-TIMI 38 trial data

BACKGROUND

Prasugrel is a newly marketed antiplatelet drug with improved cardiac outcomes as compared with clopidogrel for acute coronary syndromes involving percutaneous coronary intervention (PCI). Analysis of a subset of the TRITON-TIMI 38 trial demonstrated that cytochrome P450 2C19 (CYP2C19) reduced-function genotypes are associated with differential clinical responses to clopidogrel, but not prasugrel. Whether the CYP2C19 genotype has the potential to influence clinical choice of these drugs prior to PCI for individuals with unstable angina or non-ST segment elevation myocardial infarction is currently uncertain.

METHODS AND RESULTS

An exploratory, secondary analysis was undertaken to estimate the clinical benefit of prasugrel over clopidogrel in subgroups defined by CYP2C19 genotype, by integrating the published results of the genetic substudy and the overall TRITON-TIMI 38 trial. Individuals with a CYP2C19 reduced-metabolizer genotype were estimated to have a substantial reduction in the risk of the composite primary outcome (cardiovascular death, myocardial infarction, or stroke) with prasugrel as compared with clopidogrel [relative risk (RR) 0.57; 95% confidence interval (CI) 0.39-0.83]. For CYP2C19 extensive metabolizers (∼70% of the population), however, the composite outcome risks with prasugrel and clopidogrel were not substantially different (RR 0.98; 95% CI 0.80-1.20).

CONCLUSIONS

Integration of the TRITON-TIMI 38 data suggests that the CYP2C19 genotype can discriminate between individuals who receive extensive benefit from using prasugrel instead of clopidogrel, and individuals with comparable clinical outcomes with prasugrel and clopidorel. Thus, CYP2C19 genotyping has the potential to guide the choice of antiplatelet therapy, and further research is warranted to validate this estimate.

Cost effectiveness of pharmacogenomics: a critical and systematic review

The use of pharmacogenetic testing in clinical practice is limited thus far. A potential barrier to the widespread implementation of pharmacogenetic testing is the lack of evidence on whether testing provides good value for money. The objective of this review was to provide a systematic and critical review of economic evaluations of pharmacogenetic testing. A literature search using publically available databases was performed for articles published up to October 2009. To be included, studies had to meet the definition of being a pharmacogenomic study (defined as use of information on human genetic variation to target drug therapy) and an economic evaluation (defined as an evaluation of both costs and clinical outcomes). Articles that met these criteria were subsequently reviewed and graded using the Quality of Health Economic Studies (QHES) instrument. Lastly, the evidence for biomarker validity and utility were qualitatively assessed using expert opinion. A total of 34 articles were identified using our defined criteria. The most common disease category was thromboembolic-related diseases (26%), while the most common biomarkers were thiopurine methyltransferase and cytochrome P450 2C9 (18% each). Almost all studies were published after 2004 (91%). Two types of studies were identified: cost-effectiveness studies and cost-utility studies, with roughly half of the overall studies being cost-utility studies (53%) and a majority of these published within the last 3 years. The average quality score was 77 (range 29-99). Of the biomarkers reviewed, it was estimated that most had demonstrated clinical validity, but only two had demonstrated clinical utility. Despite a recent increase in the number of economic evaluations of pharmacogenetic applications, further studies examining the clinical validity and utility of these biomarkers are needed to support cost-effectiveness assessments.

Proton pump inhibitors and recurrent bleeding in peptic ulcer disease

Peptic ulcer disease (PUD) is one of the main lesions responsible for upper gastrointestinal (GI) bleeding, as well as esophageal varices and Mallory-Weiss tear. Helicobacter pylori and non-steroidal anti-inflammatory drugs (NSAIDs)/aspirin are the major responsible causes. In cases of upper GI bleeding, urgent endoscopy is performed after stabilization of vital signs. There are several modalities for controlling bleeding in PUD, such as ethanol injection or hypertonic saline with epinephrine. Recurrent bleeding occurs in 20% of patients after endoscopic therapy. The combination of endoscopic intervention and a proton pump inhibitor (PPI) is necessary to achieve hemostasis of active bleeding. It has been reported that high-dose omeprazole (80 mg bolus injection, then 8 mg/h continuous infusion for 72 h, then 40 mg/day orally for 1 week) can reduce recurrent bleeding, the need for surgery and mortality from hemorrhagic shock in patients with high-risk peptic ulcer bleeding, as compared with standard-dose omeprazole. The metabolism of PPIs is dependent upon P450 2C19 genotypes and the clinical usefulness of genotypic analysis remains to be determined.

Global pharmacogenetics: genetic substructure of Eurasian populations and its effect on variants of drug-metabolizing enzymes

AIMS

To study the frequency distribution of cytochrome P450 (CYP) functional genetic variants in five Eurasian populations from the territory of Siberia in Russia.

MATERIALS & METHODS

Unrelated healthy Tuvinians, Buryats, Altaians, Yakuts and Russians (n = 87-88) were genotyped for CYP2C9*2, CYP2C9*3, CYP2C19*2, CYP2C19*3, CYP3A5*3 and CYP3A5*6. Standard pairwise genetic distances, locus-specific and global Fst statistics were calculated.

RESULTS

CYP allele and genotype frequencies demonstrated significant variability. Overall, the degree of between-population variance displayed by CYP SNPs was lower than that recorded from neutral short tandem repeats and Alu-insertion polymorphism, indicating evolutionary conservation of CYP polymorphisms. CYP-based genetic distances were well correlated with the geographic distances across populations (r = 0.822, p = 0.008).

CONCLUSIONS

Although the tested variants were present in the neighboring, yet secluded, populations at the expected range of frequencies, the observed frequencies were significantly variable across Eurasian populations, indicating potential relevance to clinical decision making.

Phenotype-genotype analysis of CYP2C19 in Colombian mestizo individuals

Background

Omeprazole is metabolized by the hepatic cytochrome P450 (CYP) 2C19 enzyme to 5-hydroxyomeprazole. CYP2C19 exhibits genetic polymorphisms responsible for the presence of poor metabolizers (PMs), intermediate metabolizers (IMs) and extensive metabolizers (EMs). The defective mutations of the enzyme and their frequencies change between different ethnic groups; however, the polymorphism of the CYP2C19 gene has not been studied in Colombian mestizos. The aim of this study was to evaluate the genotype and phenotype status of CYP2C19 in Colombian mestizos, in order to contribute to the use of appropriate strategies of drug therapy for this population.

Methods

189 subjects were genotyped using the multiplex SNaPshot technique and a subgroup of 44 individuals received 20 mg of omeprazole followed by blood collection at 3 hours to determine the omeprazole hydroxylation index by HPLC.

Results

83.6%, 15.3% and 1.1% of the subjects were genotyped as EMs, IMs and PMs, respectively. The frequencies of the CYP2C29*1 and CYP2C19*2 alleles were 91.3% and 8.7% respectively whereas the *3, *4, *5, *6 and *8 alleles were not found. No discrepancies were found between the genotype and phenotype of CYP2C19.

Conclusion

The frequency of poor metabolizers (1.1%) in the Colombian mestizos included in this study is similar to that in Bolivian mestizos (1%) but lower than in Mexican-Americans (3.2%), West Mexicans (6%), Caucasians (5%) and African Americans (5.4%). The results of this study will be useful for drug dosage recommendations in Colombian mestizos.

The AmpliChip CYP450 test: principles, challenges, and future clinical utility in digestive disease

Understanding genetically encoded inherited differences in drug metabolism and targets (ie, receptors, transporters) offers the promise of minimizing adverse drug reactions and improving therapies. Among the enzymes involved in drug metabolism, the cytochromes P450 (CYP450) hold a central position. In fact, CYP450 are involved in the biotransformation of most drugs used in clinical practice. Recent advances in the development of DNA-based diagnostics, coupled with a better understanding of genetic polymorphisms in influencing pharmacologic responses, have provided the foundation for novel in vitro tests that may predict side effects and/or therapeutic responses. The AmpliChip CYP450 test was developed as a clinical test to evaluate an individual's metabolic capacity for certain drugs by identifying polymorphisms of 2 CYP450 enzymes (ie, CYP2D6 and CYP2D19). Even though the AmpliChip CYP450 has been approved by the US Food and Drug Administration, its practical clinical utility has not yet been determined, and there is a paucity of data related to gastrointestinal and liver diseases. An understanding of the principles and opportunities provided by this new category of diagnostic test is key before planning the necessary studies to evaluate the usefulness of AmpliChip CYP450 in gastroenterologic clinical practice.

The effect of CYP2C19 polymorphisms on H. pylori eradication rate in dual and triple first-line PPI therapies: a meta-analysis

PREMISE

It has been suggested that proton pump inhibitor (PPI)-related differences in Helicobacter pylori eradication rates are partly because of CYP2C19 polymorphisms and there have been conflicting data in this area. We conducted a meta-analysis to investigate the evidence relating CYP2C19 to first-line H. pylori eradication rates.

METHODS

A search of the literature was conducted up to June 2005 using Medline, EMBase, and Cochrane Register of Controlled Trials (CENTRAL). Twenty-eight arms from 17 papers were extracted for omeprazole, lansoprazole, and rabeprazole, collectively. Review Manager 4.2.8 was used for analysis.

RESULTS

When all eradication rates, regardless of PPI used, were combined there was no significant difference between poor metabolizers (PM) and heterozygous extensive metabolizers (HetEMs) (odds ratio [OR]= 1.35, 95% confidence interval [CI] 0.89-2.07, p = 0.15); however, there was a significant difference between HetEM and homozygous extensive metabolizers (HomEMs) (OR = 1.90, 95% CI 1.38-2.60, p < 0.0001). Significant heterogeneity was observed in a HomEM and PM comparison, hence additional subanalysis of individual PPIs revealed that dual and triple omeprazole therapies significantly favored higher H. pylori eradication rates in PM over HomEM (OR = 4.03, 95% CI 1.97-8.28, p = 0.0001), and also over HetEM (OR = 2.24, 95% CI 1.09-4.61, p = 0.03). Dual and triple rabeprazole and triple lansoprazole therapies did not show significantly different H. pylori eradication rates between PM and HomEM (OR = 1.04, 95% CI 0.44-2.46, p = 0.25) and (OR = 1.80, 95% CI 0.67-4.85, p = 0.93), respectively.

CONCLUSIONS

The impact of CYP2C19 polymorphisms on H. pylori eradication rates in studied populations appears clinically relevant in patients prescribed omeprazole as a component of their dual- or triple-drug therapy, whereas regimens that include lansoprazole or rabeprazole are unaffected. The choice of PPI and/or dose rather than CYP2C19 genotyping could be a more practical approach to assure the highest H. pylori eradication rates in clinical settings.

Voriconazole therapeutic drug monitoring

We report on 28 patients who underwent voriconazole monitoring because of disease progression or toxicity. A relationship (P<0.025) between disease progression and drug concentration was detected. Favorable responses were observed in 10/10 patients with concentrations above 2.05 microg/ml, while disease progressed in 44% (n=18) of patients with concentrations below 2.05 microg/ml.

Papel del polimorfismo genético CYP2C19 en los efectos adversos a fármacos y en el riesgo para diversas enfermedades

There are a great number of polymorphic genes in the human genome. Many of them codify enzymes that metabolizes drugs and xenobiotic agents, including carcinogens. Among the better known of them, there are a number of isozymes of the microsomal oxidative system (CYP3A4, CYP2C9, CYP2C19 y CYP2D6). This article reviews the following issues: a) frequency of presentation of the "poor metabolizer" genotype and/or phenotype for substrates of CYP2C19; b) role of CYP2C19 polymorphism on the metabolism of some drugs (mephenytoine and other antiepileptic drugs, proton pump inhibitors, several antidepressants and anxyolitics, the antimalaria aggent proguanyl, and propranolol, among others, use this metabolic pathway), and c) possible role of CYP2C19 polymorphism in the risk for development of neoplasia and other diseases (systemic lupus erythematosus, psoriasis, hip osteonecrosis, Alzheimer's disease, amyotrophic lateral sclerosis, essential tremor).

Possible Interethnic Differences in Omeprazole Pharmacokinetics

BACKGROUND AND OBJECTIVE

Considerable ethnic differences have been reported in the incidence of the poor metaboliser (PM) genotype of cytochrome P450 (CYP) 2C19. The frequency of this genotype was found to be much higher in Oriental persons (13-23%) than in American or European populations (3-5%). There are, however, no valid data published for Arabic subjects. The present study was conducted to evaluate pharmacokinetic parameters of omeprazole after a single dose in healthy Jordanian Arabic subjects and to compare the results with data published for other populations.

METHODS

Seventy-four healthy male Jordanian Arabic volunteers contributed to the study, which was performed at Al Essra Hospital in Amman, Jordan. After an overnight fast, omeprazole was administered as a single Losec 20mg capsule. A total of 20 blood samples were collected over a 10-hour period after administration. Omeprazole pharmacokinetic parameters were determined from the plasma concentration-time profiles using the WinNonlin software. Kolmogorov-Smirnov's test and probit plots of omeprazole area under the plasma concentration-time curve (AUC) data were used to analyse the frequency distribution of phenotypic data.

RESULTS

The mean pharmacokinetic parameters and their corresponding coefficient of variation (CV%) for peak plasma concentration (Cmax), AUC from time zero to infinity (AUCinfinity), time to reach Cmax (tmax), apparent oral clearance (CL/F) and elimination half-life (t(1/2)) were 314.96 ng/mL (56%), 923.2 ng . h/mL (108.6%), 2.1h (44%), 0.66 L/h/kg (92%) and 1.5 h (56.6%), respectively. Interindividual differences in the current study were high for all pharmacokinetic parameters, yet comparable to CVs reported in nonphenotyped subjects identified within other ethnic groups (40.3-159% for AUC and 39-48.2% for Cmax). The frequency distribution of all parameters, particularly the AUC, was shown to be trimodal. This has proposed the presence of three distinct phenotypes, designated as extensive metabolisers (EMs), slow-extensive metabolisers (SEMs), and PMs, with corresponding frequency of 36.5%, 39.2% and 24.3%, respectively. After stratification, the relative mean AUCs of omeprazole in EMs, SEMs and PMs were 1 : 2.7 : 9.3 (all p < 0.001). Accordingly, the CL/F of omeprazole showed a ratio of 9.8 : 3.6 : 1 for three phenotype groups, respectively. For other pharmacokinetic parameters including Cmax, t1/2, AUC normalised for bodyweight (AUCN), Cmax/dose and AUC/dose, there were also significant differences between the three groups.

CONCLUSIONS

The current pharmacokinetic study revealed that the majority of the Jordanian Arabics seemed to be more properly classified within the EM phenotype. More specifically, the observed metabolic rates of heterozygous and homozygous Jordanian Arabic EMs were more comparable to those of Caucasian EMs than Oriental EMs. Consequently, higher dosage requirements can be expected among most of the Jordanian Arabics. Yet, the incidence of PMs is significant and they seemed to exhibit a similar pharmacokinetic pattern to Chinese PMs in terms of long-term exposure (clearance and AUC) as well as short-term exposure (Cmax) parameters, after adjustment for dose and bodyweight. Therefore, further clinical application of CYP2C19 polymorphism is anticipated in Jordanian Arabic mixed population, particularly if long-term use of omeprazole is intended.

Cytochrome P450 gene-based drug prescribing and factors impacting translation into routine clinical practice

Pharmacogenetics represents a rapidly advancing, competitive field of investigation. Due to the potential for clinically recognizable interactions between a set of old polymorphic genes and a relatively new environmental insult (drugs), many human geneticists believe that variability in the drug-metabolizing enzyme systems will soon translate into clinical practice across entire populations. Despite this, the field has not yet received widespread clinical acceptance. This article will review the common cytochrome P450 gene polymorphisms and discuss the factors that may facilitate (or attenuate) their translation into clinical practice.

Molecular biology methods for the characterization of Helicobacter pylori infections and their diagnosis

Helicobacter pylori infects approximately half of the human population; however, the outcome of infection is affected by many factors, including strain and host genotype characteristics and bacterial density within the stomach. Many molecular methods have been developed to provide information with respect to these characteristics. Methods that provide results within 24 h of endoscopy may be used to develop individualized treatment that is more effective, results in fewer side effects, cuts costs,decreases the number of treatment failures and results in the development of fewer antibiotic-resistant H. pylori strains.

Helicobacter pylori infection: anything new should we know?

Over the past year, 2003-4, there have been a number of studies consolidating previous work in relation to pathogenesis of disease, diagnosis and management of Helicobacter pylori. Studies into the pathogenesis of disease have identified the main adhesin of H. pylori as an important virulence marker and as a potential target for therapy. Molecular investigations of both the strain and host variations have identified the action of several of the virulence factors, e.g. cagA, vacA, on disrupting host cell signalling and the consequences in respect of the release of chemokines from the damaged gastric epithelium and the effect on apoptosis. Over the past year, there have been further diagnostic kits developed based on modifications of current technology. Two promising areas of research for diagnosis are the use of host/strain genome polymorphisms as a means of identifying high-risk patients who may develop severe disease and the use of proteomics to identify potential antigens of diagnostic (or therapeutic) use. The three main antibiotics that are used in first-line eradication regimens are clarithromycin, metronidazole and amoxycillin. Of these, metronidazole has the highest prevalence of resistance, followed by clarithromycin; amoxycillin resistance is only rarely reported. The decreasing success of current first-line therapy is the driving force for the development of new antibiotic combinations and a search for novel sources for chemotherapeutic agents and novel therapeutic targets.

Helicobacter pylori: current status and future prospects

Helicobacter pylori is a global pathogen that causes severe gastrointestinal diseases leading to a significant morbidity and mortality. There is an effective treatment for peptic ulcer disease, however, this is being compromised by an increase in the prevalence of antibiotic resistance. Although alternative rescue regimens have been advocated, the best strategy would be to prevent disease, especially in the case of gastric cancer for which there is still no treatment. One approach is to inhibit the first step in the pathogenic process - adhesion of the organism to the host tissue. Another and probably a better approach is vaccination, but clinical trials have so far been unsuccessful. There is still a large uncertainty in relation to how H. pylori causes disease. Knowledge from genomics, proteomics, and the relationship between polymorphism of the bacterium and the host, as well as the continuing investigation of the role played by important virulence factors in the outcome of the disease, will help both in understanding pathogenesis of disease and in the design of the best vaccine.