CYP2D6 basic genotyping as a potential tool to improve the antiemetic efficacy of ondansetron in prophylaxis of postoperative nausea and vomiting

Pharmacogenetic Testing for the Pediatric Gastroenterologist: Actionable Drug-Gene Pairs to Know

Gastroenterologists represent some of the earlier adopters of precision medicine through pharmacogenetic testing by embracing upfront genotyping for thiopurine S-methyltransferase nucleotide diphosphatase (TPMT) before prescribing 6-mercaptopurine or azathioprine for the treatment of inflammatory bowel disease. Over the last two decades, pharmacogenetic testing has become more readily available for other genes relevant to drug dose individualization. Common medications prescribed by gastroenterologists for conditions other than inflammatory bowel disease now have actionable guidelines, which can improve medication efficacy and safety; however, a clear understanding of how to interpret the results remains a challenge for many clinicians, precluding wide implementation of genotype-guided dosing for drugs other than 6-mercaptopurine and azathioprine. Our goal is to provide a practical tutorial on the currently available pharmacogenetic testing options and a results interpretation for drug-gene pairs important to medications commonly used in pediatric gastroenterology. We focus on evidence-based clinical guidelines published by the Clinical Pharmacogenetics Implementation Consortium (CPIC^®) to highlight relevant drug-gene pairs, including proton pump inhibitors and selective serotonin reuptake inhibitors and cytochrome P450 (CYP) 2C19, ondansetron and CYP2D6, 6-mercaptopurine and TMPT and Nudix hydrolase 15 (NUDT15), and budesonide and tacrolimus and CYP3A5.

Postoperative nausea and vomiting: risk factors, prediction tools, and algorithms

PURPOSE OF REVIEW

Postoperative/postdischarge nausea and vomiting (PONV/PDNV) remain relevant issues in perioperative care. Especially in ambulatory surgery, PONV can prevent discharge or lead to unplanned readmission.

RECENT FINDINGS

The evidence for the management of PONV is now quite good but is still inadequately implemented. A universal, multimodal rather than risk-adapted approach for PONV prophylaxis is now recommended. The evidence on PDNV is insufficient.

SUMMARY

PDNV management is based primarily on consequent prophylaxis and therapy of PONV.

Pediatric CYP2D6 metabolizer status and post-tonsillectomy nausea and vomiting after ondansetron

The goal of this study was to determine whether CYP2D6 metabolizer status within the ondansetron-treated pediatric tonsillectomy population is associated with risk of postoperative nausea and vomiting (PONV) in the post-anesthesia care unit. We conducted a retrospective cohort study of pediatric patients (<18 years) who underwent tonsillectomy and received ondansetron on the day of the procedure. Data were obtained from BioVU, an institutional biobank that links DNA to de-identified electronic health record data. Subjects were tested for 10 CYP2D6 allelic variants and copy number variation, and genotype data translated into CYP2D6 metabolizer status. The cohort included 652 individuals, 105 (16.1%) of whom had PONV. Rates of PONV were similar across groups: ultrarapid metabolizers (UMs), 1 of 9 (11.1%); normal metabolizers (NMs), 64 of 354 (18.1%); intermediate metabolizers (IMs), 33 of 234 (14.1%); poor metabolizers (PMs), 6 of 39 (15.4%); and ambiguous phenotypes, 1 of 16 (6.3%). In multivariable analysis adjusted for age, sex, and time under anesthesia, CYP2D6 metabolizer status was not associated with PONV, with an odds ratio of 1.37 (95% confidence interval 0.9, 2.1) when comparing PM/IM versus NM/UM. In this large pediatric population, no significant differences were detected for PONV based on CYP2D6 metabolizer status. Further investigation is needed to determine mechanisms for ondansetron inefficacy in children.

Pharmacogenetic and clinical predictors of ondansetron failure in a diverse pediatric oncology population

PURPOSE

Chemotherapy-induced nausea and vomiting (CINV) is a frequently seen burdensome adverse event of cancer therapy. The 5-HT3 receptor antagonist ondansetron has improved the rates of CINV but, unfortunately, up to 30% of patients do not obtain satisfactory control. This study examined whether genetic variations in a relevant drug-metabolizing enzyme (CYP2D6), transporter (ABCB1), or receptor (5-HT3) were associated with ondansetron failure.

METHODS

DNA was extracted from blood and used to genotype: ABCB1 (3435C > T (rs1045642) and G2677A/T (rs2032582)), 5-HT3RB (rs3758987 T > C and rs45460698 (delAAG/dupAAG)), and CYP2D6 variants. Ondansetron failure was determined by review of the medical records and by patient-reported outcomes (PROs).

RESULTS

One hundred twenty-nine patients were approached; 103 consented. Participants were less than 1 to 33 years (mean 6.85). A total of 39.8% was female, 58.3% was White (22.3% Black, 19.4% other), and 24.3% was Hispanic. A majority had leukemia or lymphoma, and 41 (39.8%) met the definition of ondansetron failure. Of variants tested, rs45460698 independently showed a significant difference in risk of ondansetron failure between a mutant (any deletion) and normal allele (p = 0.0281, OR 2.67). Age and BMI were both predictive of ondansetron failure (age > 12 (OR 1.12, p = 0.0012) and higher BMI (OR 1.13, p = 0.0119)). In multivariate analysis, age > 12 was highly predictive of ondansetron failure (OR 7.108, p = 0.0008). rs45460698 was predictive when combined with an increased nausea phenotype variant of rs1045642 (OR 3.45, p = 0.0426).

CONCLUSION

Select phenotypes of 5-HT3RB and ABCB1, age, and potentially BMI can help predict increased risk for CINV in a diverse pediatric oncology population.

Influence of CYP2D6 metabolizer status on ondansetron efficacy in pediatric patients undergoing hematopoietic stem cell transplantation: A case series

Chemotherapy‐induced nausea and vomiting (CINV) is commonly experienced by patients receiving antineoplastic agents prior to hemopoietic stem cell transplant (HSCT). Ondansetron, a 5‐HT3 antagonist metabolized by CYP2D6, is an antiemetic prescribed to treat short‐term CINV, but some patients still experience uncontrolled nausea and vomiting while taking ondansetron. Adult CYP2D6 ultrarapid metabolizers (UMs) are at higher risk for CINV due to rapid ondansetron clearance, but similar studies have not been performed in pediatric patients. We performed a retrospective chart review of 128 pediatric HSCT recipients who received ondansetron for CINV prevention and had CYP2D6 genotyping for 20 alleles and duplication detection. The number of emetic episodes for each patient was collected from the start of chemotherapy through 7 days after HSCT. The average age of the cohort was 6.6 years (range: 0.2–16.7) and included three UMs, 72 normal metabolizers, 47 intermediate metabolizers, and six poor metabolizers. Because UMs are the population at risk for inefficacy, we describe the course of treatment for these three patients, as well as the factors influencing emesis: chemotherapy emetogenicity, diagnosis, and duration of ondansetron administration. The cases described support guidelines recommending non‐CYP2D6 metabolized antiemetics (e.g., granisetron) when a patient is a known CYP2D6 UM, but pediatric studies with a larger sample of CYP2D6 UMs are needed to validate our findings.

CYP2D6 Basic Genotyping of Patients with Chronic Pain Receiving Tramadol or Codeine. A Study in a Greek Cohort

OBJECTIVE

To assess CYP2D6 genotype prevalence in chronic pain patients treated with tramadol or codeine.

DESIGN

Prospective cohort study.

SETTING

General hospital, pain management unit.

SUBJECTS

Patients with chronic pain, treated with codeine or tramadol.

METHODS

Patients' pain was assessed at baseline (numeric rating scale [NRS]; 0-10). Prescription of codeine or tramadol was selected randomly. The assessment of patients' response to the drug in terms of pain relief and adverse effects was performed after 24 hours. Reduction of pain intensity of >50% or an NRS <4 was considered a positive response. Patients' blood samples were collected during the first visit. Genotyping for the common variants CYP2D6 *2, *3, *4, *5, *6, *9, *10, *14, and *17 was performed, and alleles not carrying any polymorphic allele were classified as CYP2D6*1 (wild-type [wt]).

RESULTS

Seventy-six consecutive patients were studied (20 males, 56 females), aged 21-85 years. Thirty-four received tramadol and 42 codeine. The main genotypes of CYP2D6 identified were the wt/wt (35.5%), the *4/wt (17.1%), and the *6/wt (10.5%). Adverse effects were common, especially in carriers of *9/*9, *5/*5, *5/*4, and *10/*10, as well as in variants including the 4 allele (*4/*1 [38.4%] and *4/*4 [42.8%]).

CONCLUSIONS

Genotyping can facilitate personalized pain management with opioids, as specific alleles are related to decreased efficacy and adverse effects.

Postoperative Nausea and Vomiting in Pediatric Patients

Postoperative nausea and vomiting (PONV), postoperative vomiting (POV), post-discharge nausea and vomiting (PDNV), and opioid-induced nausea and vomiting (OINV) continue to be causes of pediatric morbidity, delay in discharge, and unplanned hospital admission. Research on the pathophysiology, risk assessment, and therapy for PDNV, OINV and pain therapy options in children has received increased attention. Multimodal pain management with the use of perioperative regional and opioid-sparing analgesia has helped decrease nausea and vomiting. Two common emetogenic surgical procedures in children are adenotonsillectomy and strabismus repair. Although PONV risk factors differ between adults and children, the approach to decrease baseline risk is similar. As PONV and POV are frequent in children, antiemetic prophylaxis should be considered for those at risk. A multimodal approach for antiemetic and pain therapy involves preoperative risk evaluation and stratification, antiemetic prophylaxis, and pain management with opioid-sparing medications and regional anesthesia. Useful antiemetics include dexamethasone and serotonin 5-hydroxytryptamine-3 (5-HT3) receptor antagonists such as ondansetron. Multimodal combination prophylactic therapy using two or three antiemetics from different drug classes and propofol total intravenous anesthesia should be considered for children at high PONV risk. "Enhanced recovery after surgery" protocols include a multimodal approach with preoperative preparation, adequate intravenous fluid hydration, opioid-sparing analgesia, and prophylactic antiemetics. PONV guidelines and management algorithms help provide effective postoperative care for pediatric patients.

Is there a place for genetics in the management of PONV?

Antiemetic prophylaxis for postoperative nausea and vomiting (PONV) - a frequent complication in the postoperative period - is routinely given to high-risk patients. However, standard PONV risk models do not account for genetic factors, which have been shown to have a significant influence on PONV incidence and drug response. In this review, we describe the polymorphisms of various genes (serotonin, dopamine, cholinergic, etc.) and how pharmacogenomics is involved in the pathophysiology of PONV. This review also addresses how genetics is involved in today's clinical practice related to PONV and how it will change in the upcoming years as personalized medicine advances.

Management strategies for the treatment and prevention of postoperative/postdischarge nausea and vomiting: an updated review

Postoperative nausea and vomiting (PONV) and postdischarge nausea and vomiting (PDNV) remain common and distressing complications following surgery. The routine use of opioid analgesics for perioperative pain management is a major contributing factor to both PONV and PDNV after surgery. PONV and PDNV can delay discharge from the hospital or surgicenter, delay the return to normal activities of daily living after discharge home, and increase medical costs. The high incidence of PONV and PDNV has persisted despite the introduction of many new antiemetic drugs (and more aggressive use of antiemetic prophylaxis) over the last two decades as a result of growth in minimally invasive ambulatory surgery and the increased emphasis on earlier mobilization and discharge after both minor and major surgical procedures (e.g. enhanced recovery protocols). Pharmacologic management of PONV should be tailored to the patient’s risk level using the validated PONV and PDNV risk-scoring systems to encourage cost-effective practices and minimize the potential for adverse side effects due to drug interactions in the perioperative period. A combination of prophylactic antiemetic drugs with different mechanisms of action should be administered to patients with moderate to high risk of developing PONV. In addition to utilizing prophylactic antiemetic drugs, the management of perioperative pain using opioid-sparing multimodal analgesic techniques is critically important for achieving an enhanced recovery after surgery. In conclusion, the utilization of strategies to reduce the baseline risk of PONV (e.g. adequate hydration and the use of nonpharmacologic antiemetic and opioid-sparing analgesic techniques) and implementing multimodal antiemetic and analgesic regimens will reduce the likelihood of patients developing PONV and PDNV after surgery.

CHRM3 rs2165870 Polymorphism Correlates with Postoperative Nausea and Vomiting Incidence and the Efficacy of Ondansetron in a Chinese Han Population

Background

Previous GWAS studies have shown that there is a relationship between M3 muscarinic acetylcholine receptor (CHRM3) rs2165870 polymorphism and postoperative nausea and vomiting (PONV) incidence. However, no Chinese studies have addressed this issue.

Methods

To explore the relationship between CHRM3 rs2165870 polymorphism and PONV incidence in a Chinese Han population, we enrolled 512 patients receiving elective surgery in this study. CHRM3 rs2165870 polymorphism was genotyped using PCR-RFLP method.

Results

We found that AA genotype or A allele of CHRM3 rs2165870 polymorphism elevated the risk of PONV (AA versus GG; OR, 2.88; 95% CI, 1.51-5.47; P = 0.001; A versus G; OR, 1.39; 95% CI, 1.07-1.81; P = 0.013). In addition, CHRM3 rs2165870 polymorphism was related to the risk of PONV among the males, smokers, and those individuals with Apfel Score 3-4 or ASA classification 2-3. Last, we assessed the effects of CHRM3 rs2165870 polymorphism on the treatment efficacy of ondansetron for PONV. Data uncovered that 103 of 209 patients (49.3%) showed response to ondansetron treatment for PONV. The PONV incidence was significantly higher in AA genotype carriers compared with GG genotype carriers during the first 2 h after surgery, but not from 2 to 24 h after surgery.

Conclusion

To sum up, this study reveals that CHRM3 rs2165870 polymorphism is related to the incidence of PONV and treatment effects of ondansetron for preventing PONV in this Chinese Han population.