Use of Pharmacogenomics to Guide Proton Pump Inhibitor Therapy in Clinical Practice

Impact of medication dosage on Helicobacter pylori eradication rates among pediatric patients

OBJECTIVES

Helicobacter pylori rates of eradication to common first-line regimens continue to decline globally. Prescription of the appropriate medication dosage is an important consideration, particularly in the pediatric population due to medication weight-based dosing. Limited data is available on the impact of guideline-recommended weight-based dosing on the successful eradication of H. pylori in children.

METHODS

Retrospective study of patients with histologic evidence of H. pylori from two pediatric tertiary care centers in New England. We excluded patients who were not treated or those missing eradication data. We compared the eradication rates of patients prescribed recommended weight-based dosages, duration, and frequency of treatment with those who were not.

RESULTS

One hundred forty-four patients were included. The overall eradication rate was 73.6% (106/144). All treatment regimens were properly prescribed for 14 days. There was a high rate of improper weight-based dosing: proton pump inhibitor (PPI) 31.2% (45/144), amoxicillin 31.7% (39/123), metronidazole (MET) 19.4% (12/62), clarithromycin (CLA) 23.9% (22/70), tetracycline 50% (6/12), bismuth 26.1% (6/23). When PPIs were properly weight-dosed, there was a 78.8% eradication rate that dropped to 62.2% with suboptimal dosing (p = 0.036, odds ratio [OR]: 2.26, confidence interval [CI]: 1.04-4.87). When amoxicillin was properly weight-dosed, successful eradication was achieved in 81% versus only 53.8% when improperly dosed (p = 0.002; OR: 3.64, CI: 1.58-8.37). There was no statistically significant impact on eradication rates with improper weight-based dosing of MET, CLA, tetracycline, or bismuth.

CONCLUSION

Proper weight-based dosing of amoxicillin and PPI is important for the successful eradication of H. pylori among children in the New England area.

Proton-Pump Inhibitors in Eosinophilic Esophagitis: A Review Focused on the Role of Pharmacogenetics

Proton-pump inhibitors (PPIs) are the most administered first-line treatment for eosinophilic esophagitis (EoE). However, only around half of EoE patients respond histologically to a double dosage of PPI. In addition, 70% of responders maintain EoE in remission after tapering the PPI dose. In order to avoid endoscopy with biopsies-the only accurate method of assessing PPI response-efforts have been made to identify PPI responder patients. The clinical or endoscopic features and biomarkers evaluated so far, however, have not proven to be sufficient in predicting PPI response. Although new approaches based on omics technologies have uncovered promising biomarkers, the specialized and complex procedures required are difficult to implement in clinical settings. Alternatively, PPI pharmacogenetics based on identifying variations in CYP2C19 and STAT6 genes have shown promising results in EoE, and could easily be performed in most laboratories. Other genetic variations have also been associated with PPI response and may explain those cases not related to CYP2C19 or STAT6. Here, we provide an overview of PPI treatment in EoE and evidence of how genetic variations in CYP2C19 and other genes could affect PPI effectiveness, and also discuss studies evaluating the role of pharmacogenetics in predicting PPI response in patients with EoE.

Combined contributions of cytochrome P450s (CYPs) and non-enzymatic metabolism in the in vitro biotransformation of anaprazole, a novel proton pump inhibitor

Anaprazole, a new proton pump inhibitor (PPI), is designed for the treatment of acid-related diseases, such as gastric ulcers and gastroesophageal reflux. This study explored the in vitro metabolic transformation of anaprazole. The metabolic stabilities of anaprazole in human plasma and human liver microsomes (HLM) were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Then, the contribution (%) of non-enzymatic and cytochrome P450s (CYPs) enzyme-mediated anaprazole metabolism was assessed. To obtain the metabolic pathways of anaprazole, the metabolites generated in HLM, thermal deactivated HLM, and cDNA-expressed recombinant CYPs incubation systems were identified by ultra-performance liquid chromatography/quadrupole-time-of-flight mass spectrometry (UPLC/Q-TOF-MS). Results showed that anaprazole was very stable in human plasma and unstable in HLM. The contribution (%) of non-enzymatic vs. CYPs enzyme-mediated metabolism was 49% vs. 51%. CYP3A4 was the major enzyme (48.3%), followed by CYP2C9 (17.7%) and CYP2C8 (12.3%), in responsible for the metabolism of anaprazole. Specific chemical inhibitors targeting CYP enzymes notably blocked the metabolic transformation of anaprazole. Six metabolites of anaprazole were identified in the non-enzymatic system, whereas 17 metabolites were generated in HLM. The biotransformation reactions mainly included sulfoxide reduction to thioether, sulfoxide oxidation to sulfone, deoxidation, dehydrogenation, O-dealkylation or O-demethylation of thioether, O-demethylation and dehydrogenation of thioether, O-dealkylation and dehydrogenation of thioether, thioether O-dealkylation and dehydrogenation of thioether, and O-dealkylation of sulfone. Both enzymatic and non-enzymatic metabolisms contribute to the clearance of anaprazole in human. Anaprazole is less likely to develop drug-drug interactions in clinical use compared to other PPIs.

Dual therapy for Helicobacter pylori infection

ABSTRACT

Bismuth-containing quadruple therapy (BQT) has long been recommended for Helicobacter pylori ( H. pylori ) eradication in China. Meanwhile, in the latest national consensus in China, dual therapy (DT) comprising an acid suppressor and amoxicillin has also been recommended. In recent years, the eradication rate of H. pylori has reached >90% using DT, which has been used not only as a first-line treatment but also as a rescue treatment. Compared with BQT, DT has great potential for H. pylori eradication; however, it has some limitations. This review summarizes the development of DT and its application in H. pylori eradication. The H. pylori eradication rates of DT were comparable to or even higher than those of BQT or standard triple therapy, especially in the first-line treatment. The incidence of adverse events associated with DT was lower than that with other therapies. Furthermore, there were no significant differences in the effects of dual and quadruple therapies on gastrointestinal microecology. In the short term, H. pylori eradication causes certain fluctuations in the gastrointestinal microbiota; however, in the long term, the gastrointestinal microbiota eventually returns to its normal state. In the penicillin-naïve population, patients receiving DT have a high eradiation rate, better compliance, lower incidence of adverse reactions, and lower primary and secondary resistance to amoxicillin. These findings suggest the safety, efficacy, and potential of DT for H. pylori eradication.

Evaluation of the relationship between polymorphisms in CYP2C19 and the single-dose pharmacokinetics of omeprazole in healthy Chinese volunteers: A multicenter study

The aim of this study was to evaluate the relationship between polymorphisms in CYP2C19 and the single‐dose pharmacokinetics (PKs) of omeprazole in healthy Chinese volunteers. A 20 mg single dose of omeprazole (Losec) enteric‐coated capsules or tablets was orally administered to 656 healthy subjects from eight subcenters. The polymorphic alleles of CYP2C19*2, *3, and *17 were determined by Sanger sequencing and Agena mass array. Plasma concentrations of omeprazole were determined by high‐performance liquid‐chromatography tandem mass spectrometry. PK parameters of area under the concentration versus time curve (AUC)_0‐t, AUC from zero to infinity (AUC_0‐∞), maximum plasma concentration (C_max), and terminal half‐life (t_1/2) were significantly influenced by CYP2C19 phenotype (all p < 0.001) and diplotype (all p < 0.001), and the same results were obtained in the subgroup analysis of the effects of diet and dosage form. The polymorphisms of CYP2C19*2(rs4244285; all PK parameters p < 0.001) and *3(rs4986893; p_Cmax = 0.020, and the p values of other PK parameters were less than 0.001) were significantly associated with the PKs of omeprazole. For CYP2C19*17 (rs12248560), only t_1/2 showed a significant correlation (p = 0.032), whereas other PK parameters did not. The present study demonstrated that the Pks of omeprazole is greatly influenced by CYP2C19.