Codeine-related adverse drug reactions in children following tonsillectomy: a prospective study

The Role of Pharmacogenomics in Opioid Prescribing

Pharmacogenomics is increasingly important to guide objective, safe, and effective individualised prescribing. Personalised prescribing has revolutionised treatments in the past decade, allowing clinicians to maximise drug efficacy and minimise adverse effects based on a person’s genetic profile. Opioids, the gold standard for cancer pain relief, are among the commonest medications prescribed in palliative care practice. This narrative review examines the literature surrounding opioid pharmacogenomics and its applicability to the palliative care cancer population. There is currently limited intersection between the fields of palliative care and pharmacogenomics, but growing evidence presents a need to build linkages between the two disciplines. Pharmacogenomic evidence guiding opioid prescribing is currently available for codeine and tramadol, which relates to CYP2D6 gene variants. However, these medications are prescribed less commonly for pain in palliative care. Research is accelerating with other opioids, where oxycodone (CYP2D6) and methadone (CYP2B6, ABCB1) already have moderate evidence of an association in terms of drug metabolism and downstream analgesic response and side effects. OPRM1 and COMT are receiving increasing attention and have implications for all opioids, with changes in opioid dosage requirements observed but they have not yet been studied widely enough to be considered clinically actionable. Current evidence indicates that incorporation of pharmacogenomic testing into opioid prescribing practice should focus on the CYP2D6 gene and its actionable variants. Although opioid pharmacogenomic tests are not widely used in clinical practice, the progressively reducing costs and rapid turnover means greater accessibility and affordability to patients, and thus, clinicians will be increasingly asked to provide guidance in this area. The upsurge in pharmacogenomic research will likely discover more actionable gene variants to expand international guidelines to impact opioid prescribing. This rapidly expanding area requires consideration and monitoring by clinicians in order for key findings with clinical implications to be accessible, meaningfully interpretable and communicated.

Molecular monitoring of patient response to painkiller drugs

INTRODUCTION

Non-steroidal anti-inflammatory drugs and opioids are widely prescribed for the treatment of mild to severe pain. Wide interindividual variability regarding the analgesic efficacy and adverse reactions to these drugs (ADRs) exist, although the mechanisms responsible for these ADRs are not well understood.

AREAS COVERED

We provide an overview of the clinical impact of variants in genes related to the pharmacokinetics and pharmacodynamics of painkillers, as well as those associated with the susceptibility to ADRs. Also, we discuss the current pharmacogenetic-guided treatment recommendations for the therapeutic use of non-steroidal anti-inflammatory drugs and opioids.

EXPERT OPINION

In the light of the data analyzed, common variants in genes involved in pharmacokinetics and pharmacodynamics processes may partially explain the lack of response to painkiller treatment and the occurrence of adverse drug reactions. The implementation of high-throughput sequencing technologies may help to unveil the role of rare variants as considerable contributors to explaining the interindividual variability in drug response. Furthermore, a consensus between the diverse pharmacogenetic guidelines is necessary to extend the implementation of pharmacogenetic-guided prescription in daily clinical practice. Additionally, the physiologically-based pharmacokinetics and pharmacodynamics modeling techniques may contribute to the improvement of these guidelines and facilitate clinicians drug dose adjustment.

High-Dose Acetaminophen Alters the Integrity of the Blood-Brain Barrier and Leads to Increased CNS Uptake of Codeine in Rats

The consumption of acetaminophen (APAP) can induce neurological changes in human subjects; however, effects of APAP on blood-brain barrier (BBB) integrity are unknown. BBB changes by APAP can have profound consequences for brain delivery of co-administered drugs. To study APAP effects, female Sprague-Dawley rats (12-16 weeks old) were administered vehicle (i.e., 100% dimethyl sulfoxide (DMSO), intraperitoneally (i.p.)) or APAP (80 mg/kg or 500 mg/kg in DMSO, i.p.; equivalent to a 900 mg or 5600 mg daily dose for a 70 kg human subject). BBB permeability was measured via in situ brain perfusion using [¹⁴C]sucrose and [³H]codeine, an opioid analgesic drug that is co-administered with APAP (i.e., Tylenol #3). Localization and protein expression of tight junction proteins (i.e., claudin-5, occludin, ZO-1) were studied in rat brain microvessels using Western blot analysis and confocal microscopy, respectively. Paracellular [¹⁴C]sucrose "leak" and brain [³H]codeine accumulation were significantly enhanced in rats treated with 500 mg/kg APAP only. Additionally, claudin-5 localization and protein expression were altered in brain microvessels isolated from rats administered 500 mg/kg APAP. Our novel and translational data show that BBB integrity is altered following a single high APAP dose, results that are relevant to patients abusing or misusing APAP and/or APAP/opioid combination products.

CYP2D6 phenotypes and opioid metabolism: the path to personalized analgesia

INTRODUCTION

Opioids play a fundamental role in chronic pain, especially considering when 1 of 5 Europeans adults, even more in older females, suffer from it. However, half of them do not reach an adequate pain relief. Could pharmacogenomics help to choose the most appropriate analgesic drug?

AREAS COVERED

The objective of the present narrative review was to assess the influence of cytochrome P450 2D6 (CYP2D6) phenotypes on pain relief, analgesic tolerability, and potential opioid misuse. Until December 2021, a literature search was conducted through the MEDLINE, PubMed database, including papers from the last 10 years. CYP2D6 plays a major role in metabolism that directly impacts on opioid (tramadol, codeine, or oxycodone) concentration with differences between sexes, with a female trend toward poorer pain control. In fact, CYP2D6 gene variants are the most actionable to be translated into clinical practice according to regulatory drug agencies and international guidelines.

EXPERT OPINION

CYP2D6 genotype can influence opioids' pharmacokinetics, effectiveness, side effects, and average opioid dose. This knowledge needs to be incorporated in pain management. Environmental factors, psychological together with genetic factors, under a sex perspective, must be considered when you are selecting the most personalized pain therapy for your patients.

Choosing Wisely Canada - pediatric otolaryngology recommendations

The Choosing Wisely Canada campaign raises awareness amongst physicians and patients regarding unnecessary or inappropriate tests and treatments. Using an online survey, members of the Pediatric Otolaryngology Subspecialty Group within the Canadian Society of Otolaryngology – Head & Neck Surgery developed a list of nine evidence based recommendations to help physicians and patients make treatment decisions regarding common pediatric otolaryngology presentations: (1) Don’t routinely order a plain film x-ray in the evaluation of nasal fractures; (2) Don’t order imaging to distinguish acute bacterial sinusitis from an upper respiratory infection; (3) Don’t place tympanostomy tubes in most children for a single episode of otitis media with effusion of less than 3 months duration; (4) Don’t routinely prescribe intranasal/systemic steroids, antihistamines or decongestants for children with uncomplicated otitis media with effusion; (5) Don’t prescribe oral antibiotics for children with uncomplicated tympanostomy tube otorrhea or uncomplicated acute otitis externa; (6) Don’t prescribe codeine for post-tonsillectomy/adenoidectomy pain relief in children; (7) Don’t administer perioperative antibiotics for elective tonsillectomy in children; (8) Don’t perform tonsillectomy for children with uncomplicated recurrent throat infections if there have been fewer than 7 episodes in the past year, 5 episodes in each of the past 2 years, or 3 episodes in each of the last 3 years; and (9) Don’t perform endoscopic sinus surgery for uncomplicated pediatric chronic rhinosinusitis prior to failure of maximal medical therapy and adenoidectomy.

Clinical Pharmacogenetics Implementation Consortium Guideline for CYP2D6, OPRM1, and COMT Genotypes and Select Opioid Therapy

Opioids are mainly used to treat both acute and chronic pain. Several opioids are metabolized to some extent by CYP2D6 (codeine, tramadol, hydrocodone, oxycodone, and methadone). Polymorphisms in CYP2D6 have been studied for an association with the clinical effect and safety of these drugs. Other genes that have been studied for their association with opioid clinical effect or adverse events include OPRM1 (mu receptor) and COMT (catechol-O-methyltransferase). This guideline updates and expands the 2014 Clinical Pharmacogenetics Implementation Consortium (CPIC) guideline for CYP2D6 genotype and codeine therapy and includes a summation of the evidence describing the impact of CYP2D6, OPRM1, and COMT on opioid analgesia and adverse events. We provide therapeutic recommendations for the use of CYP2D6 genotype results for prescribing codeine and tramadol and describe the limited and/or weak data for CYP2D6 and hydrocodone, oxycodone, and methadone, and for OPRM1 and COMT for clinical use.

Reviewing pharmacogenetics to advance precision medicine for opioids

BACKGROUND

Adequate opioid prescribing is critical for therapeutic success of pain management. Despite the widespread use of opioids, optimized opioid therapy remains unresolved with risk of accidental lethal overdosing. With the emergence of accumulating evidence linking genetic variation to opioid response, pharmacogenetic based treatment recommendations have been proposed.

OBJECTIVE

The aim of this review is to evaluate pharmacogenetic evidence and provide an overview on genes involved in the pharmacokinetics and pharmacodynamics of opioids.

METHODS

For this review, a systematic literature search of published articles was used in PubMed®, with no language restriction and between the time period of January 2000 to December 2020. We reviewed randomized clinical studies, study cohorts and case reports that investigated the influence of genetic variants on selected opioid pharmacokinetics and pharmacodynamics. In addition, we reviewed current CPIC clinical recommendations for pharmacogenetic testing.

RESULTS

Results of this review indicate consistent evidence supporting the association between selected genetic variants of CYP2D6 for opioid metabolism. CPIC guidelines include recommendations that indicate the avoidance of tramadol use, in addition to codeine, in CYP2D6 poor metabolizers and ultrarapid metabolizers, and to monitor intermediate metabolizers for less-than-optimal response. While there is consistent evidence for OPRM1 suggesting increased postoperative morphine dosing requirements in A118G G-allele carriers, the clinical relevance remains limited.

CONCLUSION

There is emerging evidence of clinical relevance of CYP2D6 and, to a lesser extent, OPRM1 polymorphism in personalized opioid drug dosing. As a result, first clinics have started to implement pharmacogenetic guidelines for CYP2D6 and codeine.

Patterns of dispensed opioids after tonsillectomy in children and adolescents in South Carolina, United States, 2010-2017

OBJECTIVES

Tonsillectomy (with or without adenoidectomy) is a common pediatric surgical procedure requiring post-operative analgesia. Because of the respiratory depression effects of opioids, clinicians strive to limit the use of these drugs for analgesia post-tonsillectomy. The objective of this study was to identify demographic and medication use patterns predictive of persistent opioid dispensing (as a proxy for opioid use) to pediatric patients post-tonsillectomy.

PATIENTS AND METHODS

Retrospective cohort of South Carolina (USA) Medicaid-insured children and adolescents 0-18 years old without malignancy who had tonsillectomy in 2014-2017. We evaluated opioid dispensing pre-surgery and in the 30 days exposure period after hospital discharge. The main outcome, persistent opioid dispensing, was defined as any subject dispensed ≥1 opioid prescription 90-270 days after discharge. Group-based trajectory analyses described post-procedure opioid dispensing trajectories.

RESULTS

There were 11,578 subjects representing 12,063 tonsillectomy procedures. Few (3.5%) procedures were followed by persistent opioid dispensing. Any opioid dispensing during the exposure period was associated with an increased odds of persistent opioid dispensing status during the follow up period (OR 1.51 for 1-6 days of exposure and OR 1.65 for 7-30 days of opioid exposure), as was pre-procedure opioid dispensing, having >1 tonsillectomy procedure, and having complex chronic medical conditions. Group-based trajectory analyses identified 4 distinct patterns of post-discharge opioid dispensing.

CONCLUSIONS

Any opioid dispensing during the 30 days after tonsillectomy increased the odds of persistent opioid dispensing by > 50%. Multivariable and group-based trajectory analyses identified patient and procedure variables that correlate with persistent opioid dispensing, primarily driven by groups receiving pre-tonsillectomy opioids and a second group who experienced multiple episodes of tonsillectomy.

Gene-Based Dose Optimization in Children

Pharmacogenetics is a key component of precision medicine. Genetic variation in drug metabolism enzymes can lead to variable exposure to drugs and metabolites, potentially leading to inefficacy and drug toxicity. Although the evidence for pharmacogenetic associations in children is not as extensive as for adults, there are several drugs across diverse therapeutic areas with robust pediatric data indicating important, and relatively common, drug-gene interactions. Guidelines to assist gene-based dose optimization are available for codeine, thiopurine drugs, selective serotonin reuptake inhibitors, atomoxetine, tacrolimus, and voriconazole. For each of these drugs, there is an opportunity to clinically implement precision medicine approaches with children for whom genetic test results are known or are obtained at the time of prescribing. For many more drugs that are commonly used in pediatric patients, additional investigation is needed to determine the genetic factors influencing appropriate dose.

Clinical Practice Guideline: Tonsillectomy in Children (Update)

OBJECTIVE

This update of a 2011 guideline developed by the American Academy of Otolaryngology-Head and Neck Surgery Foundation provides evidence-based recommendations on the pre-, intra-, and postoperative care and management of children 1 to 18 years of age under consideration for tonsillectomy. Tonsillectomy is defined as a surgical procedure performed with or without adenoidectomy that completely removes the tonsil, including its capsule, by dissecting the peritonsillar space between the tonsil capsule and the muscular wall. Tonsillectomy is one of the most common surgical procedures in the United States, with 289,000 ambulatory procedures performed annually in children <15 years of age based on the most recent published data. This guideline is intended for all clinicians in any setting who interact with children who may be candidates for tonsillectomy.

PURPOSE

The purpose of this multidisciplinary guideline is to identify quality improvement opportunities in managing children under consideration for tonsillectomy and to create explicit and actionable recommendations to implement these opportunities in clinical practice. Specifically, the goals are to educate clinicians, patients, and/or caregivers regarding the indications for tonsillectomy and the natural history of recurrent throat infections. Additional goals include the following: optimizing the perioperative management of children undergoing tonsillectomy, emphasizing the need for evaluation and intervention in special populations, improving the counseling and education of families who are considering tonsillectomy for their children, highlighting the management options for patients with modifying factors, and reducing inappropriate or unnecessary variations in care. Children aged 1 to 18 years under consideration for tonsillectomy are the target patient for the guideline. For this guideline update, the American Academy of Otolaryngology-Head and Neck Surgery Foundation selected a panel representing the fields of nursing, anesthesiology, consumers, family medicine, infectious disease, otolaryngology-head and neck surgery, pediatrics, and sleep medicine.

KEY ACTION STATEMENTS

The guideline update group made strong recommendations for the following key action statements (KASs): (1) Clinicians should recommend watchful waiting for recurrent throat infection if there have been <7 episodes in the past year, <5 episodes per year in the past 2 years, or <3 episodes per year in the past 3 years. (2) Clinicians should administer a single intraoperative dose of intravenous dexamethasone to children undergoing tonsillectomy. (3) Clinicians should recommend ibuprofen, acetaminophen, or both for pain control after tonsillectomy. The guideline update group made recommendations for the following KASs: (1) Clinicians should assess the child with recurrent throat infection who does not meet criteria in KAS 2 for modifying factors that may nonetheless favor tonsillectomy, which may include but are not limited to multiple antibiotic allergies/intolerance, PFAPA (periodic fever, aphthous stomatitis, pharyngitis, and adenitis), or history of >1 peritonsillar abscess. (2) Clinicians should ask caregivers of children with obstructive sleep-disordered breathing and tonsillar hypertrophy about comorbid conditions that may improve after tonsillectomy, including growth retardation, poor school performance, enuresis, asthma, and behavioral problems. (3) Before performing tonsillectomy, the clinician should refer children with obstructive sleep-disordered breathing for polysomnography if they are <2 years of age or if they exhibit any of the following: obesity, Down syndrome, craniofacial abnormalities, neuromuscular disorders, sickle cell disease, or mucopolysaccharidoses. (4) The clinician should advocate for polysomnography prior to tonsillectomy for obstructive sleep-disordered breathing in children without any of the comorbidities listed in KAS 5 for whom the need for tonsillectomy is uncertain or when there is discordance between the physical examination and the reported severity of oSDB. (5) Clinicians should recommend tonsillectomy for children with obstructive sleep apnea documented by overnight polysomnography. (6) Clinicians should counsel patients and caregivers and explain that obstructive sleep-disordered breathing may persist or recur after tonsillectomy and may require further management. (7) The clinician should counsel patients and caregivers regarding the importance of managing posttonsillectomy pain as part of the perioperative education process and should reinforce this counseling at the time of surgery with reminders about the need to anticipate, reassess, and adequately treat pain after surgery. (8) Clinicians should arrange for overnight, inpatient monitoring of children after tonsillectomy if they are <3 years old or have severe obstructive sleep apnea (apnea-hypopnea index ≥10 obstructive events/hour, oxygen saturation nadir <80%, or both). (9) Clinicians should follow up with patients and/or caregivers after tonsillectomy and document in the medical record the presence or absence of bleeding within 24 hours of surgery (primary bleeding) and bleeding occurring later than 24 hours after surgery (secondary bleeding). (10) Clinicians should determine their rate of primary and secondary posttonsillectomy bleeding at least annually. The guideline update group made a strong recommendation against 2 actions: (1) Clinicians should not administer or prescribe perioperative antibiotics to children undergoing tonsillectomy. (2) Clinicians must not administer or prescribe codeine, or any medication containing codeine, after tonsillectomy in children younger than 12 years. The policy level for the recommendation about documenting recurrent throat infection was an option: (1) Clinicians may recommend tonsillectomy for recurrent throat infection with a frequency of at least 7 episodes in the past year, at least 5 episodes per year for 2 years, or at least 3 episodes per year for 3 years with documentation in the medical record for each episode of sore throat and ≥1 of the following: temperature >38.3°C (101°F), cervical adenopathy, tonsillar exudate, or positive test for group A beta-hemolytic streptococcus.

DIFFERENCES FROM PRIOR GUIDELINE

(1) Incorporating new evidence profiles to include the role of patient preferences, confidence in the evidence, differences of opinion, quality improvement opportunities, and any exclusion to which the action statement does not apply. (2) There were 1 new clinical practice guideline, 26 new systematic reviews, and 13 new randomized controlled trials included in the current guideline update. (3) Inclusion of 2 consumer advocates on the guideline update group. (4) Changes to 5 KASs from the original guideline: KAS 1 (Watchful waiting for recurrent throat infection), KAS 3 (Tonsillectomy for recurrent infection with modifying factors), KAS 4 (Tonsillectomy for obstructive sleep-disordered breathing), KAS 9 (Perioperative pain counseling), and KAS 10 (Perioperative antibiotics). (5) Seven new KASs: KAS 5 (Indications for polysomnography), KAS 6 (Additional recommendations for polysomnography), KAS 7 (Tonsillectomy for obstructive sleep apnea), KAS 12 (Inpatient monitoring for children after tonsillectomy), KAS 13 (Postoperative ibuprofen and acetaminophen), KAS 14 (Postoperative codeine), and KAS 15a (Outcome assessment for bleeding). (6) Addition of an algorithm outlining KASs. (7) Enhanced emphasis on patient and/or caregiver education and shared decision making.

Opioid Use for Treatment of Acute Pain Among Children and Adolescents Enrolled in the Mississippi Medicaid Program

BACKGROUND

Abuse of opioids among children and adolescents has become a major public concern in the United States. Understanding the epidemiology of opioid use in this vulnerable population is critical to address opioid abuse.

OBJECTIVE

The aim of this study is to characterize opioid use for the treatment of acute pain among children and adolescents enrolled in Mississippi Medicaid and to determine the effects of related clinical factors (ie, mental health disorders and obstructive sleep apnea [OSA] on patterns of opioid use.

METHODS

A retrospective cohort study was conducted using the Mississippi Medicaid administrative claims data from October 2015 through December 2017. We examined the proportion of children and adolescents less than 21 years of age using opioids within 7 days following any qualifying acute pain episode, as well as the difference in opioid use patterns between individuals with various demographic and clinical characteristics.

RESULTS

Over 5% of the eligible population received opioids within 7 days of a qualifying pain episode. The majority received schedule II or schedule III to IV short-acting opioids. There was no significant difference in opioid use for acute pain between individuals with and without a mental health disorder. Opioid use for acute pain was significantly more likely among those with a history of OSA than those without OSA.

CONCLUSION

This study characterizes the nature and patterns of opioid use among children and adolescents with acute pain. Further research is needed to understand the role of clinical and other demographic factors in the prescribing of opioids for acute pain in this population.

Children and their parents' assessment of postoperative surgical pain: Agree or disagree?

OBJECTIVE

The purpose of this study is to compare postoperative pain scores between children undergoing tonsillectomy and adenoidectomy (T&A) surgery and their parents, identify potential predictors for this disagreement, and determine possible impact on analgesic administration.

METHODS

This is a prospective longitudinal study conducted with children undergoing outpatient T&A in 4 major tertiary hospitals and their parents. Children and their parents were enrolled prior to surgery and completed baseline psychological instruments assessing parental anxiety (STAI), parental coping style (MBSS), child temperament (EAS) and parental medication administration attitude questionnaire (MAQ). Postoperatively, parents and children completed at-home pain severity ratings (Faces Pain Scale-Revised, children; Numeric Rating Scale, parents) on postoperative recovery days 1, 2, and 3, reflecting an overall pain level for the past 24 h. Parents also completed a log of analgesic administration. Based on postoperative pain scores, parent-child dyads were classified as overestimators (i.e., parents rated their child's pain higher than children rated their own pain), in agreement (i.e., rating in agreement), or underestimators (i.e., parents rated their child's pain lower than children rated their own pain).

RESULTS

A significant proportion of parent-child pairs disagreed on pain ratings on postoperative days 1-3 (30.05%-35.95%). Of those pairs in disagreement, the majority of parents overestimated their child's pain on all three postoperative days, specifically such that a total of 24-26% parents overestimated their child's pain on postoperative days 1, 2, and 3. Repeated measures ANOVA demonstrated that parents in the overestimator group administered higher, though still within safe limits, amounts of ibuprofen and oxycodone (mg/day) than did the underestimator or agreement groups. Multiple regression models showed hospital site as the only independent predictor for postoperative pain rating disagreement between children and parents.

CONCLUSIONS

Since parents overestimate their child's postoperative pain and may administer more analgesics to their child, it is essential to develop a standardized method of child pain assessment and a tailored recommended postoperative analgesic regimen amongst medical providers for children undergoing T&A.

The Society for Pediatric Anesthesia recommendations for the use of opioids in children during the perioperative period

Opioids have long held a prominent role in the management of perioperative pain in adults and children. Published reports concerning the appropriate, and inappropriate, use of these medications in pediatric patients have appeared in various publications over the last 50 years. For this document, the Society for Pediatric Anesthesia appointed a taskforce to evaluate the available literature and formulate recommendations with respect to the most salient aspects of perioperative opioid administration in children. The recommendations are graded based on the strength of the available evidence, with consensus of the experts applied for those issues where evidence is not available. The goal of the recommendations was to address the most important issues concerning opioid administration to children after surgery, including appropriate assessment of pain, monitoring of patients on opioid therapy, opioid dosing considerations, side effects of opioid treatment, strategies for opioid delivery, and assessment of analgesic efficacy. Regular updates are planned with a re-release of guidelines every 2 years.

Beneficial effects of dexmedetomidine on early postoperative cognitive dysfunction in pediatric patients with tonsillectomy

According to clinical investigations, early postoperative cognitive dysfunction is the most common adverse event in pediatric patients after tonsillectomy. A previous study has indicated that dexmedetomidine (DEX) is an efficient drug for the treatment of postoperative cognitive dysfunction. However, the efficacy of DEX in alleviating early postoperative cognitive dysfunction in pediatric patients following tonsillectomy has remained elusive, which was therefore assessed in the present study. A total of 186 children presenting with cognitive dysfunction subsequent to tonsillectomy were recruited to analyze the efficacy of DEX. Patients were randomly divided into two groups and received intravenous treatment with DEX (n=112) or placebo (n=74). Duration of treatment, dose-limiting toxicities (DLT) and maximum tolerated dose (MTD) of DEX were evaluated in a preliminary experiment. The improvement of postoperative cognitive function in children with tonsillectomy was analyzed with a Mini-Mental State Examination (MMSE) following treatment with DEX. A 40-item quality of life (MONEX-40) questionnaire was used to assess the efficacy of DEX. The plasma levels of interleukin (IL)-6, IL-1, tumor necrosis factor (TNF)-α, superoxide dismutase (SOD), neuron-specific enolase (NSE), C-reactive protein (CRP), cortisol and melatonin were also analyzed. The preliminary experiment determined that the DLT was 10 mg/kg and the MTD was 15 mg/kg. In the major clinical trial, it was revealed that MMSE scores in the DEX treatment group were markedly improved, indicating that DEX had a beneficial effect in pediatric patients with early postoperative cognitive dysfunction after tonsillectomy. In addition, IL-1and TNF-α were downregulated, while IL-6 and SOD were upregulated in patients with cognitive dysfunction after treatment with DEX compared with those in the placebo group. Furthermore, DEX treatment markedly decreased the serum levels of CRP, NSE cortisol and melatonin, which are associated with the occurrence of postoperative cognitive dysfunction in pediatric patients following tonsillectomy. In conclusion, intravenous administration of DEX at a dose of 10 mg/kg improves postoperative cognitive function in pediatric patients with tonsillectomy by decreasing the serum levels of inflammatory factors and stress-associated signaling molecules. Trial registration no. QLSDHOS0200810102C (Qilu Hospital of Shandong University, Jinan, China).

Stargazer: a software tool for calling star alleles from next-generation sequencing data using CYP2D6 as a model

Purpose

Genotyping CYP2D6 is important for precision drug therapy because it metabolizes approximately 25% of drugs and its activity varies considerably among individuals. Genotype analysis of CYP2D6 is challenging due to its highly polymorphic nature. Over 100 haplotypes (star alleles) have been defined for CYP2D6, some involving a gene conversion with its nearby non-functional but highly homologous paralog CYP2D7. We present Stargazer, a new bioinformatics tool that uses next-generation sequencing (NGS) data to call star alleles for CYP2D6 (https://stargazer.gs.washington.edu/stargazerweb/). Stargazer is currently being extended for other pharmacogenes.

Methods

Stargazer identifies star alleles from NGS data by detecting single nucleotide variants, insertion-deletion variants, and structural variants. Stargazer detects structural variation including gene deletions, duplications, and conversions by calculating paralog-specific copy number from read depth.

Results

We applied Stargazer to NGS data of 32 ethnically diverse HapMap trios that were genotyped by TaqMan assays, long-range PCR, quantitative multiplex PCR, High Resolution Melt analysis, and/or Sanger sequencing. CYP2D6 genotyping by Stargazer was 99.0% concordant with data obtained by these methods and showed 28.1% of the samples had structural variation including CYP2D6/CYP2D7 hybrids.

Conclusion

Accurate genotyping of pharmacogenes with NGS and subsequent allele calling with Stargazer will aid the implementation of precision drug therapy.

Pharmacogenetics: Applications to Pediatric Patients

Individual genomic differences may affect drug disposition and effects of many drugs, and identification of biomarkers are crucial to personalize dosage and optimize response. In children, developmental changes associated with growth and maturation translate into different relationships between genotype and phenotype and different responses to treatment compared to adults. This review aims to summarize some developmental aspects of pharmacogenetics, based on practical examples.

Use of analgesics in France, following dextropropoxyphene withdrawal

Background

In 2009, the European Medicines Agency recommended withdrawal of dextropropoxyphene (DXP); in March 2011 it was withdrawn from the market in France. Up until that time the combination dextropropoxyphene-paracetamol (DXP/PC) was widely used for analgesia. At withdrawal, French regulators recommended that DXP/PC be replaced by other step 2 analgesics, i.e. tramadol, codeine, or opium-containing drugs, or by PC for a weak level of pain. To investigate prescribing behaviours after DXP/PC withdrawal, dispensations of analgesics before and after withdrawal were analysed.

Methods

Aggregated dispensation data of analgesics prescribed between January 2009 and December 2012 in the Rhône-Alpes region were obtained from the general health insurance claims data; changes in analgesic dispensation over time were analysed with the ATC/DDD methodology. Pre (Jan-June 2009) and post-withdrawal (Jan-June 2012) changes of DDDs where computed for each analgesic step.

Results

The dispensations of DXP/PC experienced a two-step decrease until 2011. Over the withdrawal period 2009-2012, there was a 14% decrease in the overall use of analgesic (from 109 to 94 DDDs), while the use of step 2 analgesics declined by 46% (− 22 DDDs, from 47 to 25 DDDs). This latter decline included a cessation of use of DXP/PC (29 DDDs in 2009) that were only in part (+ 7 DDDs, from 18 to 25 DDDs) compensated by increased use of codeine, tramadol and opium, in monotherapy or combined with PC. For step 1 analgesics, use increased with 9%, mostly PC (+ 8 DDDs, from 31 to 39 DDDs). Step 3 analgesics dispensations remained largely unchanged over this period (around 3 DDDs).

Conclusions

In the Rhône-Alpes region, DXP/PC withdrawal was accompanied in part by an increased use of same level analgesics, and in part by an increased use of PC in monotherapy. The extent of DXP/PC use before withdrawal, and the increased use of PC after DXP withdrawal, underline the complexity of pain management.

Pharmacogenetics and application in pediatrics

Identification of markers involved in drug disposition is crucial for drugs with a narrow therapeutic index. Individual genomic differences can affect the pharmacology of some drugs and participate to inter-individual variability in drug response. Pharmacogenetics is a useful tool in clinical practice for dosage adjustment and to limit drug toxicities. In pediatrics, physiological changes can also influence the disposition of drugs in infants, children and adolescents. The importance of ontogeny translates into different responses to the same drug in children and adults. Thus, interactions between the maturation of metabolism enzymes or transporters and genetics have a major impact on drug exposure leading to age-specific dosage requirements. This review aims to describe implementation of pharmacogenetics in personalized medicine and specifies pediatric characteristics with ethical considerations.

Codeine and opioid metabolism: implications and alternatives for pediatric pain management

PURPOSE OF REVIEW

Use of perioperative opioids for surgical pain management of children presents clinical challenges because of concerns of serious adverse effects including life-threatening respiratory depression. This is especially true for children with history of obstructive sleep apnea. This review will explore current knowledge of clinically relevant factors and genetic polymorphisms that affect opioid metabolism and postoperative outcomes in children.

RECENT FINDINGS

Within the past several years, an increasing number of case reports have illustrated clinically important respiratory depression, anoxic brain injuries and even death among children receiving appropriate weight-based dosages of codeine and other opioids for analgesia at home setting particularly following tonsillectomy. Several national and international organizations have issued advisories on use of codeine in pediatrics, based on cytochrome P450 family 2 subfamily D type 6 (CYP2D6) pharmacogenetics. We have discussed the pros and cons of alternatives to codeine for pain management.

SUMMARY

Although routine preoperative genotyping to identify children at risk and personalized opioid use for pediatric perioperative pain management is still a distant reality, current known implications of CYP2D6 pharmacogenetics on codeine use shows that pharmacogenetics has the potential to guide anesthesia providers on perioperative opioid selection and dosing to maximize efficacy and safety.

Categorization and association analysis of risk factors for adverse drug events

PURPOSE

Adverse drug events (ADE) are among the leading causes of morbidity and hospitalization. This review analyzes risk factors for ADE, particularly their categorizations and association patterns, the prevalence, severity, and preventability of ADE, and method characteristics of reviewed studies.

METHODS

Literature search was conducted via PubMed, Science Direct, CINAHL, and MEDLINE. A review was conducted of research articles that reported original data about specific risk factors for ADE since 2000. Data analyses were performed using Excel and R.

RESULTS

We summarized 211 risk factors for ADE, and grouped them into five main categories: patient-, disease-, medication-, health service-, and genetics-related. Among them, medication- and disease-related risk factors were most frequently studied. We further classified risk factors within each main category into subtypes. Among them, polypharmacy, age, gender, central nervous system agents, comorbidity, service utilization, inappropriate use/change use of drugs, cardiovascular agents, and anti-infectives were most studied subtypes. An association analysis of risk factors uncovered many interesting patterns. The median prevalence, preventability, and severity rate of reported ADE was 19.5% (0.29%~86.2%), 36.2% (2.63%~91%), and 16% (0.01%~47.4%), respectively.

CONCLUSIONS

This review introduced new categories and subtypes of risk factors for ADE. The broad and in-depth coverage of risk factors and their association patterns elucidate the complexity of risk factor analysis. Managing risk factors for ADE is crucial for improving patient safety, particularly for the elderly, comorbid, and polypharmacy patients. Some under-explored risk factors such as genetics, mental health and wellness, education, lifestyle, and physical environment invite future research.

Clinical Pharmacogenetics of Cytochrome P450-Associated Drugs in Children

Cytochrome P450 (CYP) enzymes are commonly involved in drug metabolism, and genetic variation in the genes encoding CYPs are associated with variable drug response. While genotype-guided therapy has been clinically implemented in adults, these associations are less well established for pediatric patients. In order to understand the frequency of pediatric exposures to drugs with known CYP interactions, we compiled all actionable drug-CYP interactions with a high level of evidence using Clinical Pharmacogenomic Implementation Consortium (CPIC) data and surveyed 10 years of electronic health records (EHR) data for the number of children exposed to CYP-associated drugs. Subsequently, we performed a focused literature review for drugs commonly used in pediatrics, defined as more than 5000 pediatric patients exposed in the decade-long EHR cohort. There were 48 drug-CYP interactions with a high level of evidence in the CPIC database. Of those, only 10 drugs were commonly used in children (ondansetron, oxycodone, codeine, omeprazole, lansoprazole, sertraline, amitriptyline, citalopram, escitalopram, and risperidone). For these drugs, reports of the drug-CYP interaction in cohorts including children were sparse. There are adequate data for implementation of genotype-guided therapy for children for three of the 10 commonly used drugs (codeine, omeprazole and lansoprazole). For the majority of commonly used drugs with known CYP interactions, more data are required to support pharmacogenomic implementation in children.

Prior opioid exposure influences parents' sharing of their children's CYP2D6 research results

AIM

To determine parents' use of their children's CYP2D6 research result. We hypothesized that perceived utility, likelihood of sharing and actual sharing of results would differ between parents with children previously exposed (cases) or unexposed (controls) to opioids.

METHODS

We returned results by phone (baseline). We surveyed parents about perceived utility and likelihood of sharing their child's research result at baseline, and actual sharing at 3 and 12 months.

RESULTS

Cases were more likely than controls to agree that they (p = 0.022) and the doctors (p = 0.041) could use the results to care for their child, to report higher likelihood of sharing (p = 0.042) and to actually share results with the child's doctor (p = 0.026).

CONCLUSION

Prior opioid exposure influenced perceived clinical utility and sharing behaviors.

A Comparison of Nonopioid and Opioid Oral Analgesia following Pediatric Palatoplasty

Objective

This article evaluates postoperative analgesia in pediatric palatoplasty patients using nonopioid oral medications.

Design

This study was a retrospective chart review.

Setting

The setting for this study was a tertiary-care children's hospital.

Participants

Study participants were pediatric patients who underwent palatoplasty procedures performed by a single surgeon.

Interventions

Interventions included nonopioid and opioid oral medications for postoperative analgesia.

Main Outcome Measures

The adequacy of nonopioid versus opioid oral analgesia was assessed by (1) time to discontinue IV fluid, (2) total IV morphine doses for breakthrough pain, (3) daily IV morphine doses for breakthrough pain, (4) time to discharge from the hospital, and (5) perioperative weight change. Group comparisons of outcome measures were performed using a two one-sided test.

Results

A total of 61 patients were identified who received three standard pain regimens: acetaminophen + ibuprofen (12), hydrocodone/acetaminophen (23), and hydrocodone/acetaminophen + ibuprofen (26). There was sufficient evidence to suggest equivalence in outcome measures for acetaminophen + ibuprofen versus hydrocodone/acetaminophen and hydrocodone/acetaminophen + ibuprofen for the following: time to discontinue IV fluid ( P = .02, 90% confidence interval [CI] = –0.42 to 0.17; P = .007, 90% CI = –0.28 to 0.34), daily IV morphine doses ( P = .023, 90% [CI] = –0.83 to 0.65; P = .032, 90% [CI] = –0.92 to 0.28), time to discharge from the hospital ( P = .017, 90% [CI] = –0.40 to 0.27; P = .015, 90% [CI] = –0.24 to 0.39), and perioperative weight change ( P = .002; 90% CI = –0.25 to 0.46; P < .0001; 90% CI = –0.34 to 0.18). There was no sufficient evidence to suggest equivalence for total IV morphine doses ( P = .189, 90% CI = –1.51 to 1.78; P = .169, 90% CI = –1.51 to 0.88).

Conclusions

Oral acetaminophen and ibuprofen alone may provide similar analgesia to traditional regimens with reduced risks following pediatric palatoplasty.

The use of the FLACC pain scale in pediatric patients undergoing adenotonsillectomy

OBJECTIVES

1) Determine the usage rate of opioid pain medication after adenotonsillectomy (T&A). 2) Review the use of the Face, Legs, Activity, Cry, Consolability (FLACC) pain scale for T&A patients 3) Determine the rate of postoperative physician contacts for pain related complaints.

METHODS

A retrospective case series review was performed on 125 pediatric patients undergoing T&A and subsequent 23-hour postoperative observation at an academic tertiary care center from June-August of 2015. Postoperative pain scores using the FLACC pain scale, the utilization of opioid pain medications, and the number of postoperative contacts for pain were recorded.

RESULTS

Average age of patients was 5.7 years and 50% were female. 90% of T&A's were performed for adenotonsillar hypertrophy. The post-tonsillectomy hemorrhage rate was 4%. 70 (56%) patients required postoperative opioid pain medication, with (30) 43% of these patients requiring more than one dose. The mean number of opioid doses was 1.64 ± 0.9 and was not related to age, weight or gender. FLACC scores were highly associated (spearman correlation 0.77) with the amount of opioid medication given. Mean FLACC scores decreased over time after T&A. 20% of patients contacted a physician for unsatisfactory pain control postoperatively with 6% requiring emergency department visits and 14% contacting the office via phone call.

CONCLUSIONS

A significant portion of pediatric patients undergoing T&A require postoperative opioids for pain control. The FLACC scale is a valuable way of quantifying post-operative T&A pain in pediatric patients. Despite routine pain management postoperatively, a significant proportion of patients require contact with a physician postoperatively for pain management.

Constellation: a tool for rapid, automated phenotype assignment of a highly polymorphic pharmacogene, CYP2D6, from whole-genome sequences

An important component of precision medicine-the use of whole-genome sequencing (WGS) to guide lifelong healthcare-is electronic decision support to inform drug choice and dosing. To achieve this, automated identification of genetic variation in genes involved in drug absorption, distribution, metabolism, excretion and response (ADMER) is required. CYP2D6 is a major enzyme for drug bioactivation and elimination. CYP2D6 activity is predominantly governed by genetic variation; however, it is technically arduous to haplotype. Not only is the nucleotide sequence of CYP2D6 highly polymorphic, but the locus also features diverse structural variations, including gene deletion, duplication, multiplication events and rearrangements with the nonfunctional, neighbouring CYP2D7 and CYP2D8 genes. We developed Constellation, a probabilistic scoring system, enabling automated ascertainment of CYP2D6 activity scores from 2×100 paired-end WGS. The consensus reference method included TaqMan genotyping assays, quantitative copy-number variation determination and Sanger sequencing. When compared with the consensus reference Constellation had an analytic sensitivity of 97% (59 of 61 diplotypes) and analytic specificity of 95% (116 of 122 haplotypes). All extreme phenotypes, i.e., poor and ultrarapid metabolisers were accurately identified by Constellation. Constellation is anticipated to be extensible to functional variation in all ADMER genes, and to be performed at marginal incremental financial and computational costs in the setting of diagnostic WGS.

Opioid Prescribing and Potential Overdose Errors Among Children 0 to 36 Months Old

OBJECTIVE

To estimate the frequency of potential overdoses among outpatient opioid-containing prescriptions.

METHOD

Using 11 years of outpatient Medicaid prescription data, we compared opioid dose dispensed (observed) versus expected dose to estimate overdose error frequencies. A potential overdose was defined as any preparation dispensed that was >110% of expected based on imputed, 97th percentile weights.

RESULTS

There were 59 536 study drug prescriptions to children 0 to 36 months old. Overall, 2.7% of the prescriptions contained potential overdose quantities, and the average excess amount dispensed was 48% above expected. Younger ages were associated with higher frequencies of potential overdose. For example, 8.9% of opioid prescriptions among infants 0 to 2 months contained potential overdose quantities, compared with 5.7% among infants 3 to 5 months old, 3.6% among infants 6 to 11 months old, and 2.3% among children >12 months (P < .0001).

CONCLUSIONS

Opioid prescriptions for infants and children routinely contained potential overdose quantities.

Challenges to integrating pharmacogenetic testing into medication therapy management

Some have proposed the integration of pharmacogenetic (PGx) testing into medication therapy management (MTM) to enable further refinement of treatments to reduce risk of adverse responses and improve efficacy. PGx testing involves the analysis of genetic variants associated with therapeutic or adverse response and may be useful in enhancing the ability to identify ineffective and/or harmful drugs or drug combinations. This "enhanced" MTM might also reduce patient concerns about side effects and increase confidence that the medication is effective, addressing 2 key factors that impact patient adherence: concern and necessity. However, the feasibility and effectiveness of the integration of PGx testing into MTM in clinical practice has not yet been determined. In this commentary, we consider some of the challenges to the integration and delivery of PGx testing in MTM services.