Pharmacogenetic insights into codeine analgesia: implications to pediatric codeine use

Hydrocodone, Oxycodone, and Morphine Metabolism and Drug-Drug Interactions

Awareness of drug interactions involving opioids is critical for patient treatment as they are common therapeutics used in numerous care settings, including both chronic and disease-related pain. Not only do opioids have narrow therapeutic indexes and are extensively used, but they have the potential to cause severe toxicity. Opioids are the classical pain treatment for patients who suffer from moderate to severe pain. More importantly, opioids are often prescribed in combination with multiple other drugs, especially in patient populations who typically are prescribed a large drug regimen. This review focuses on the current knowledge of common opioid drug-drug interactions (DDIs), focusing specifically on hydrocodone, oxycodone, and morphine DDIs. The DDIs covered in this review include pharmacokinetic DDI arising from enzyme inhibition or induction, primarily due to inhibition of cytochrome p450 enzymes (CYPs). However, opioids such as morphine are metabolized by uridine-5'-diphosphoglucuronosyltransferases (UGTs), principally UGT2B7, and glucuronidation is another important pathway for opioid-drug interactions. This review also covers several pharmacodynamic DDI studies as well as the basics of CYP and UGT metabolism, including detailed opioid metabolism and the potential involvement of metabolizing enzyme gene variation in DDI. Based upon the current literature, further studies are needed to fully investigate and describe the DDI potential with opioids in pain and related disease settings to improve clinical outcomes for patients. SIGNIFICANCE STATEMENT: A review of the literature focusing on drug-drug interactions involving opioids is important because they can be toxic and potentially lethal, occurring through pharmacodynamic interactions as well as pharmacokinetic interactions occurring through inhibition or induction of drug metabolism.

Pharmacogenomics in Children

Historically genetics has not been considered when prescribing drugs for children. However, it is clear that genetics are not only an important determinant of disease in children but also of drug response for many important drugs that are core agents used in the therapy of common problems in children. Advances in therapy and in the ethical construct of children's research have made pharmacogenomic assessment for children much easier to pursue. It is likely that pharmacogenomics will become part of the therapeutic decision-making process for children, notably in areas such as childhood cancer where weighing benefits and risks of therapy is crucial.

Frequency of CYP2D6*3 and *4 and metabolizer phenotypes in three mestizo Peruvian populations

Wild type genotypes (CYP2D6) and their allelic variants have been described in a sample of a Peruvian mestizo population. The global allele frequency was 0.015 for CYP2D6*3 and 0.051 for CYP2D6*4. The percentages of genotypes described were 97% CYP2D6*1/*1 and 3.0% CYP2D6*1/*3; 90.60% for CYP2D6*1/*1, 8.55% CYP2D6*1/*4 and 0.85% CYP2D6*4/*4. The allelic frequencies of CYP2D6*3 in the Lima subpopulations were 0.022 and 0.010 for Junin; CYP2D6*4 of 0.048, 0.060, and 0.050 for residents of Lima, Junín, and Tacna, respectively. The Hardy-Weinberg equilibrium test for the studied population showed that both frequencies are in equilibrium, p <.05. The metabolizer phenotype was inferred according to the genotypes: 11.54% were classified as intermediate metabolizers (*1/*3 or *1/*4) and 0.85% as poor metabolizers (*4/*4). It is concluded that the frequencies of the CYP2D6*3 and CYP2D6*4 alleles are low for the Peruvian mestizo population compared to the Latin American and tricontinental population, due to their natural population evolution, which is manifested by their decreased metabolic activity, the same that is relevant in clinical practice.

The use of oral opioids to control children's pain in the post-codeine era

Pain is a common problem for children, and pain management comprises both pharmacologic and nonpharmacologic measures. For moderate to severe pain, oral opioids have been a popular choice for the last few decades. Codeine has historically been the best-known oral opioid for use in children. However, availability and use of codeine have sharply declined due to safety concerns. A variety of other opioids have been used in place of codeine, but data are limited regarding their efficacy and safety in children. While the same pathways metabolize oral oxycodone as codeine, oxycodone's pharmacokinetics varies widely. There are also limited data on the safety and efficacy of oral hydromorphone and tramadol use for children. Oral morphine is the opiate alternative to codeine for which there is the most evidence of safety and efficacy in children. Research is needed to investigate both other opioids and non-opioid approaches to guide evidence-based analgesic therapy and treatment for moderate-to-severe pain in children.

Les opioïdes par voie orale en remplacement de la codéine pour contrôler la douleur chez les enfants

La douleur est un problème courant chez les enfants. Des mesures pharmacologiques et non pharmacologiques sont utilisées pour la prendre en charge. Depuis quelques décennies, les opioïdes par voie orale sont populaires pour soulager la douleur modérée à grave. La codéine a longtemps été l'opioïde par voie orale le plus connu pour les enfants. Pour des raisons de sécurité, elle est désormais nettement moins accessible et moins employée. Divers autres opioïdes la remplacent, mais les données sur leur efficacité et leur sécurité sont limitées chez les enfants. L'oxycodone par voie orale emprunte les mêmes voies métaboliques que la codéine, mais sa pharmacocinétique est très variable. Les données sur la sécurité et l'efficacité de l'hydromorphone et du tramadol par voie orale chez les enfants sont également limitées. Lorsqu'on y recourt au lieu de la codéine, la morphine par voie orale est l'opiacé dont la sécurité et l'efficacité sont les mieux démontrées chez les enfants. Des recherches devront être réalisées pour explorer d'autres approches relatives aux médicaments opioïdes et non opioïdes, afin d'orienter les traitements analgésiques fondés sur des données probantes qui soulageront la douleur modérée à grave chez les enfants.

Metabolism, pharmacokinetics and selected pharmacodynamic effects of codeine following a single oral administration to horses

OBJECTIVE

To describe the pharmacokinetics and selected pharmacodynamic variables of codeine and its metabolites in Thoroughbred horses following a single oral administration.

STUDY DESIGN

Prospective experimental study.

ANIMALS

A total of 12 Thoroughbred horses, nine geldings and three mares, aged 4-8 years.

METHODS

Horses were administered codeine (0.6 mg kg-1) orally and blood was collected before administration and at various times until 120 hours post administration. Plasma and urine samples were collected and analyzed for codeine and its metabolites by liquid chromatography-mass spectrometry, and plasma pharmacokinetics were determined. Heart rate and rhythm, step counts, packed cell volume and total plasma protein were measured before and 4 hours after administration.

RESULTS

Codeine was rapidly converted to the metabolites norcodeine, codeine-6-glucuronide (C6G), morphine, morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G). Plasma codeine concentrations were best represented using a two-compartment model. The Cmax, tmax and elimination t½ were 270.7 ± 136.0 ng mL-1, 0.438 ± 0.156 hours and 2.00 ± 0.534 hours, respectively. M3G was the main metabolite detected (Cmax 492.7 ± 35.5 ng mL-1), followed by C6G (Cmax 96.1 ± 33.8 ng mL-1) and M6G (Cmax 22.3 ± 4.96 ng mL-1). Morphine and norcodeine were the least abundant metabolites with Cmax of 3.17 ± 0.95 and 1.42 ± 0.79 ng mL-1, respectively. No significant adverse or excitatory effects were observed.

CONCLUSIONS AND CLINICAL RELEVANCE

Following oral administration, codeine is rapidly metabolized to morphine, M3G, M6G, C6G and norcodeine in horses. Plasma concentrations of M6G, a presumed active metabolite of morphine, were comparable to concentrations reported previously following administration of an analgesic dose of morphine to horses. Codeine was well tolerated based on pharmacodynamic variables and behavioral observations.

Pharmacogenomic Testing In Pediatrics: Navigating The Ethical, Social, And Legal Challenges

For the past several years, the implementation of pharmacogenetic (PGx) testing has become widespread in several centers and clinical practice settings. PGx testing may be ordered at the point-of-care when treatment is needed or in advance of treatment for future use. The potential benefits of PGx testing are not limited to adult patients, as children are increasingly using medications more often and at earlier ages. This review provides some background on the use of PGx testing in children as well as mothers (prenatally and post-natally) and discusses the challenges, benefits, and the ethical, legal, and social implications of providing PGx testing to children.

Gender, genetics, and analgesia: understanding the differences in response to pain relief

Genetic variations and gender contribute significantly to the large interpatient variations in opioid-related serious adverse effects and differences in pain relief with other analgesics. Opioids are the most commonly used analgesics to relieve moderate-to-severe postoperative pain. Narrow therapeutic index and unexplained large interpatient variations in opioid-related serious adverse effects and analgesia negatively affect optimal perioperative outcomes. In surgical, experimental, chronic, and neuropathic pain models, females have been reported to have more pain than males. This review focuses on literature evidence of differences in pain relief due to multiple genetic variations and gender of the patient.

Value of Supportive Care Pharmacogenomics in Oncology Practice

Genomic medicine provides opportunities to personalize cancer therapy for an individual patient. Although novel targeted therapies prolong survival, most patients with cancer continue to suffer from burdensome symptoms including pain, depression, neuropathy, nausea and vomiting, and infections, which significantly impair quality of life. Suboptimal management of these symptoms can negatively affect response to cancer treatment and overall prognosis. The effect of genetic variation on drug response-otherwise known as pharmacogenomics-is well documented and directly influences an individual patient's response to antiemetics, opioids, neuromodulators, antidepressants, antifungals, and more. The growing body of pharmacogenomic data can now guide clinicians to select the safest and most effective supportive medications for an individual patient with cancer from the very first prescription. This review outlines a theoretical patient case and the implications of using pharmacogenetic test results to personalize supportive care throughout the cancer care continuum.

IMPLICATIONS FOR PRACTICE

Integration of palliative medicine into the cancer care continuum has resulted in increased quality of life and survival for patients with many cancer types. However, suboptimal management of symptoms such as pain, neuropathy, depression, and nausea and vomiting continues to place a heavy burden on patients with cancer. As demonstrated in this theoretical case, pharmacogenomics can have a major effect on clinical response to medications used to treat these conditions. Recognizing the value of supportive care pharmacogenomics in oncology and application into routine practice offers an objective choice for the safest and most effective treatment compared with the traditional trial and error method.

Pharmacist and Pediatrician Knowledge of Codeine Use in Children

OBJECTIVES

In 2011, approximately 1.7 million pediatric patients had a codeine-containing prescription filled at a US retail pharmacy. Numerous cases involving serious adverse effects or fatalities have been reported in children who have been prescribed codeine. In 2013, the US Food and Drug Administration added a boxed warning to avoid codeine in children after a tonsillectomy. The purpose of this study is to determine pharmacists' and pediatricians' knowledge of the boxed warning for codeine in children.

METHODS

Two separate surveys were administered to community pharmacists in Maryland, pediatricians, and pediatric residents at a single institution in Maryland. Both surveys consisted of questions regarding knowledge of the boxed warning for codeine in children.

RESULTS

There was no difference in the awareness of the boxed warning between pharmacists (48.9%, n = 43) and pediatricians (51.3%, n = 41, p = 0.88). More pharmacists knew that ultrarapid metabolizers have the risk for increased adverse events from codeine (39.5% pharmacists vs. 20% pediatricians, p = 0.01). In addition, 36% of pharmacists and 33% of pediatricians noted that it was never appropriate to use codeine in a child (p = 0.73).

CONCLUSIONS

Only half of pharmacists and pediatricians surveyed were aware of the boxed warning for codeine. One third of pharmacists and pediatricians in this study would never use codeine in a child. Therefore, more education is needed for pharmacists and pediatricians regarding the dangers of using codeine in children.

Pharmacokinetics, pharmacodynamics and pharmacogenetics associated with nonsteroidal anti-inflammatory drugs and opioids in pediatric cancer patients

INTRODUCTION

Advancing appropriate and adequate analgesic pharmacotherapy in pediatric patients with cancer is an area of clinical need. Few studies have been performed to evaluate the selection of an analgesic and appropriate dosing corresponding to analgesic effect among pediatric cancer patients. This review describes information related to pharmacokinetic, pharmacodynamic, and pharmacogenomic (when applicable) considerations for analgesics that are commonly used to manage pain experienced by pediatric patients with cancer. Areas covered: Analgesics commonly used to treat pediatric patients with malignancy patterned after the World Health Organization's 'analgesic ladder' for cancer pain management. Expert opinion: Addressing pain management safely and effectively in pediatric patients with cancer will require advances in both drug development, to increase the armament of analgesics available for children, and our pharmacologic understanding of those analgesics in current use. However, performing the necessary types of studies to develop new analgesics, or gain knowledge of existing therapy, within a population that is relatively small, diverse, and who experience pain originating from a variety of sources, is a tremendous challenge.

CYP2D6 pharmacogenetic and oxycodone pharmacokinetic association study in pediatric surgical patients

AIM

Oxycodone is partly metabolized to the active metabolite oxymorphone by hepatic CYP2D6 in the liver. Significant genetic variability in CYP2D6 activity affects oxymorphone formation. This study aimed to associate CYP2D6 genotype and oxycodone's metabolism.

METHODS

30 children were administered oral oxycodone postoperatively. Plasma levels of oxycodone and oxymorphone, and CYP2D6 genotype were analyzed. CYP2D6 genotype and oxycodone metabolism phenotype were determined based on CYP2D6 total activity score (TAS) and metabolism phenotype: poor metabolizer (PM), intermediate metabolizer (IM), extensive metabolizer (EM) or ultrarapid metabolizer (UM).

RESULTS

Compared with PM/IM subjects, significantly greater oxymorphone exposure was seen in EM subjects (p = 0.02 for C_max, p = 0.016 for AUC_0-6 and p = 0.026 for AUC_0-24). Similarly, higher TAS value was found to be associated with greater oxymorphone exposure. Higher conversion of oxycodone to oxymorphone was observed in EM subjects compared with PM/IM subjects (p = 0.0007 for C_max, p = 0.001 for AUC_0-6 and p = 0.004 for AUC_0-24).

CONCLUSION

CYP2D6 phenotypes explain metabolism of oxycodone in children, and oxymorphone exposure is higher in CYP2D6 EM phenotype. Further studies are needed to predict the occurrence of adverse event and tailor oxycodone dose for a specific CYP2D6 phenotype.

Pharmacogenetics in obstetric anesthesia

The 21st century has been billed as the era of "precision/personalized medicine." Genetic investigation of clinical syndromes may guide therapy as well as reveal previously unknown biological or pharmacological pathways that may result in novel drug therapies. Several clinical issues in obstetrics and obstetric anesthesiology have been targets for genetic investigations. These include evaluation of the genetic effects on preterm labor and the progression of labor, spinal anesthesia-induced hypotension and the response to medications used to treat hypotension, and the effect of gene variants on pain and analgesic responses. Most studies have examined specific single nucleotide polymorphisms. Findings have revealed modest effects of genetic variation without tangible impact on current clinical practice. Over the next decade, increased availability of whole exome and genome sequencing, epigenetics, large genetic databases, computational biology and other information technology, and more rapid methods of real-time genotyping may increase the impact of genetics in the clinical arena of obstetrics and obstetric anesthesia.

Cancer Drug Delivery

Advancements in cancer drug delivery have led to the development of personalized oncology care through molecularly-driven targeted therapies. Understanding molecular and cellular mechanisms which drive tumor progression and resistance is critical in managing new treatment strategies which have shifted from empiric to biomarker-directed therapy selection. Biomarker-directed therapies have improved clinical outcomes in multiple malignancies as monotherapy and in combination with other treatment modalities, however the changing scope of treatment options presents new opportunities and challenges for research. Furthermore, pharmacogenetics may provide a rationale method of personalizing anticancer drug dosing and supportive care management for oncology patients. This chapter reviews biomarker classifications and pharmacogenetics in anticancer therapy and supportive care. Examples of biomarker-directed therapies and clinical assays, in addition to future directions of molecular profiling in oncology therapy management are discussed.

Otolaryngology Concerns for Illicit and Prescription Drug Use

Concern for illicit and restricted drug use in otolaryngology is similar to other surgical specialties with a few notable exceptions. Many illicit drugs are consumed transnasally. Repeated nasal exposure to stimulants or narcotics can cause local tissue destruction that can present as chronic rhinosinusitis or nasoseptal perforation. Further, the Food and Drug Administration has taken a stance against codeine for pediatric patients undergoing adenotonsillectomy. They have identified an increased risk of death postoperatively with these medications. Because codeine has been the most commonly prescribed narcotic, this has shifted the standard practice.

Codeine: Time to Say "No"

Codeine has been prescribed to pediatric patients for many decades as both an analgesic and an antitussive agent. Codeine is a prodrug with little inherent pharmacologic activity and must be metabolized in the liver into morphine, which is responsible for codeine's analgesic effects. However, there is substantial genetic variability in the activity of the responsible hepatic enzyme, CYP2D6, and, as a consequence, individual patient response to codeine varies from no effect to high sensitivity. Drug surveillance has documented the occurrence of unanticipated respiratory depression and death after receiving codeine in children, many of whom have been shown to be ultrarapid metabolizers. Patients with documented or suspected obstructive sleep apnea appear to be at particular risk because of opioid sensitivity, compounding the danger among rapid metabolizers in this group. Recently, various organizations and regulatory bodies, including the World Health Organization, the US Food and Drug Administration, and the European Medicines Agency, have promulgated stern warnings regarding the occurrence of adverse effects of codeine in children. These and other groups have or are considering a declaration of a contraindication for the use of codeine for children as either an analgesic or an antitussive. Additional clinical research must extend the understanding of the risks and benefits of both opioid and nonopioid alternatives for orally administered, effective agents for acute and chronic pain.

Pain Management of Pediatric Musculoskeletal Injury in the Emergency Department: A Systematic Review

Background. Pain management for children with musculoskeletal injuries is suboptimal and, in the absence of clear evidence-based guidelines, varies significantly. Objective. To systematically review the most effective pain management for children presenting to the emergency department with musculoskeletal injuries. Methods. Electronic databases were searched systematically for randomized controlled trials of pharmacological and nonpharmacological interventions for children aged 0-18 years, with musculoskeletal injury, in the emergency department. The primary outcome was the risk ratio for successful reduction in pain scores. Results. Of 34 studies reviewed, 8 met inclusion criteria and provided data on 1169 children from 3 to 18 years old. Analgesics used greatly varied, making comparisons difficult. Only two studies compared the same analgesics with similar routes of administration. Two serious adverse events occurred without fatalities. All studies showed similar pain reduction between groups except one study that favoured ibuprofen when compared to acetaminophen. Conclusions. Due to heterogeneity of medications and routes of administration in the articles reviewed, an optimal analgesic cannot be recommended for all pain categories. Larger trials are required for further evaluation of analgesics, especially trials combining a nonopioid with an opioid agent or with a nonpharmacological intervention.

Reported practice variation in pediatric pain management: a survey of Canadian pediatric emergency physicians

OBJECTIVES

To describe pediatric emergency medicine (PEM) physicians' reported pain management practices across Canada and explore factors that facilitate or hinder pain management.

METHODS

This study was a prospective survey of Canadian pediatric emergency physicians. The Pediatric Emergency Research Canada physician database was used to identify participants, and a modified Dillman's Total Design Survey Method was used for recruitment.

RESULTS

The survey response rate was 68% (139 of 206). Most physicians were 31 to 50 years old (82%) with PEM training (56%) and had been in practice for less than 10 years (55%). Almost all pain screening in emergency departments (EDs) occurred at triage (97%). Twenty-four percent of physicians noted institutionally mandated pain score documentation. Ibuprofen and acetaminophen were commonly prescribed in the ED for mild to moderate pain (88% and 83%, respectively). Over half of urinary catheterizations (60%) and intravenous (53%) starts were performed without any analgesia. The most common nonpharmacologic interventions used for infants and children were pacifiers and distraction, respectively. Training background and gender of physicians affected the likelihood of using nonpharmacologic interventions. Physicians noted time restraints to be the greatest barrier to optimal pain management (55%) and desired improved access to pain medications (32%), better policies and procedures (30%), and further education (25%).

CONCLUSIONS

When analgesia was reported as provided, ibuprofen and acetaminophen were most commonly used. Both procedural and presenting pain remained suboptimally managed. There is a substantial evidence practice gap in children's ED pain management, highlighting the need for further knowledge translation strategies and policies to support optimal treatment.

Post-tonsillectomy pain control: consensus or controversy?

Pediatric post-tonsillectomy analgesia continues to be highly debated and an area of active research. Tonsillectomy pain can lead to significant patient morbidity, and incur potentially avoidable healthcare costs. Moreover, the various analgesic classes, each present their own risk profiles and unique side effects when used in children post-tonsillectomy. This review delineates the clinical and pathophysiological basis for post-tonsillectomy pain, types of analgesics and their risk profiles, as well as special considerations in this clinical population and a review of alternative analgesic treatment options. This article presents a summary of recent literature and discusses evidence-based management options to aid medical and allied health professionals who may encounter these patients.

Pharmacological Acute Migraine Treatment Strategies: Choosing the Right Drug for a Specific Patient

Background:

In our targeted review (Section 2), 12 acute medications received a strong recommendation for use in acute migraine therapy while four received a weak recommendation for use. Strong recommendations were made to avoid use of two other medications, except for exceptional circumstances. Two anti-emetics received strong recommendations for use as needed.

Objective:

To organize the available acute migraine medications into acute migraine treatment strategies in order to assist the practitioner in choosing a specific medication(s) for an individual patient.

Methods:

Acute migraine treatment strategies were developed based on the targeted literature review used for the development of this guideline (Section 2), and a general literature review. Expert consensus groups were used to refine and validate these strategies.

Results:

Based on evidence for drug efficacy, drug side effects, migraine severity, and coexistent medical disorders, our analysis resulted in the formulation of eight general acute migraine treatment strategies. These could be grouped into four categories: 1) two mild-moderate attack strategies, 2) two moderate-severe attack or NSAID failure strategies, 3) three refractory migraine strategies, and 4) a vasoconstrictor unresponsive-contraindicated strategy. In addition, strategies were developed for menstrual migraine, migraine during pregnancy, and migraine during lactation. The eight general treatment strategies were coordinated with a “combined acute medication approach” to therapy which used features of both the “stratified” and the “step care across attacks” approaches to acute migraine management.

Conclusions:

The available medications for acute migraine treatment can be organized into a series of strategies based on patient clinical features. These strategies may help practitioners make appropriate acute medication choices for patients with migraine.

Codeine should not be prescribed for breastfeeding mothers or children under the age of 12

Medical regulatory authorities, including the Food and Drug Administration and European Medicine Agency, have published restrictions regarding the use of codeine in paediatric patients and breastfeeding mothers. This review explored the various parameters that are involved in the metabolism and toxicology of codeine in these two populations.

CONCLUSION

The growing volume of data on potential serious adverse events and questionable efficacy indicates that codeine should not be prescribed for children under 12 years of age and breastfeeding mothers.

Ethical perspectives on translational pharmacogenetic research involving children

Children represent a special population characterized by dynamic changes which may affect drug safety and efficacy. The interplay of pharmacogenetics with physiological alterations that occur throughout development is an area of increasing research focus. Given the translational nature of pharmacogenetic research, it is possible that pharmacogenetic research results may possess clinically actionable information. The potential long-term implications of pharmacogenetic test results throughout the lifespan of the child, and the potential impact of the results for other members of the family need to be considered. Comprehensive counselling and communication strategies may need to be integrated as part of pharmacogenetic research studies in children.

Acute pediatric musculoskeletal pain management in North America: a practice variation survey

Children's musculoskeletal (MSK) injury pain remains poorly managed. This survey of pediatric emergency physicians and orthopedic surgeons assessed analgesia administration practices and discharge advice for children with acute MSK pain; 683 responses were received. Ibuprofen was the most commonly reported analgesic used in the emergency department (52%) and at discharge (68%). Most (85%) reported using oral opioids in the previous 6 months. Codeine use was the most commonly reported opioid used in the emergency department (38%) and at home (51%). For equal levels of pain, younger children received less opioids than older children. Younger physicians and recent graduates chose acetaminophen and codeine more than older and more experienced colleagues, who preferred ibuprofen and non-codeine containing opioid compounds (P < .001 and .006, respectively). Orthopedic surgeons reported less ibuprofen use than pediatric emergency physicians (P < .001). Choice of analgesic agents is heterogeneous among physicians and is influenced by pain severity, child's age, and physician characteristics.

Confronting the challenges of effective pain management in children following tonsillectomy

Tonsillectomy is an extremely common surgical procedure associated with significant morbidity and mortality. The post-operative challenges include: respiratory complications, post-tonsillectomy hemorrhage, nausea, vomiting and significant pain. The present model of care demands that most of these children are managed in an ambulatory setting. The recent Federal Drug Agency (FDA) warning contraindicating the use of codeine after tonsillectomy in children represents a significant change of practice for many pediatric otolaryngological surgeons. This introduces a number of other safety concerns when deciding on a safe alternative to codeine, especially since most tonsillectomy patients are managed by lay primary caregiver's at home. This review outlines the safety issues and proposes, based on currently available evidence, a preventative multi-modal strategy to manage pain, nausea and vomiting without increasing the risk of post-tonsillectomy bleeding.

National patterns of codeine prescriptions for children in the emergency department

BACKGROUND AND OBJECTIVES

National guidelines have recommended against codeine use in children, but little is known about prescribing patterns in the United States. Our objectives were to assess changes over time in pediatric codeine prescription rates in emergency departments nationally and to determine factors associated with codeine prescription.

METHODS

We performed a serial cross-sectional analysis (2001-2010) of emergency department visits for patients ages 3 to 17 years in the nationally representative National Hospital Ambulatory Medical Care Survey. We determined survey-weighted annual rates of codeine prescriptions and tested for linear trends over time. We used multivariate logistic regression to identify characteristics associated with codeine prescription and interrupted time-series analysis to assess changes in prescriptions for upper respiratory infection (URI) or cough associated with two 2006 national guidelines recommending against its use for these indications.

RESULTS

The proportion of visits (N = 189 million) with codeine prescription decreased from 3.7% to 2.9% during the study period (P = .008). Odds of codeine prescription were higher for children ages 8 to 12 years (odds ratio [OR], 1.42; 95% confidence interval [1.21-1.67]) and among providers outside the northeast. Odds were lower for children who were non-Hispanic black (OR, 0.67 [0.56-0.8]) or with Medicaid (OR, 0.84 [0.71-0.98]). The 2006 guidelines were not associated with a decline in codeine prescriptions for cough or URI visits.

CONCLUSIONS

Although there was a small decline in codeine prescription over 10 years, use for cough or URI did not decline after national guidelines recommending against its use. More effective interventions are needed to prevent codeine prescription to children.

Pharmacogenomics and adverse drug reactions in children

Adverse drug reactions are a common and important complication of drug therapy in children. Over the past decade it has become increasingly apparent that genetically controlled variations in drug disposition and response are important determinants of adverse events for many important adverse events associated with drug therapy in children. While this research has been difficult to conduct over the past decade technical and ethical evolution has greatly facilitated the ability of investigators to conduct pharmacogenomic studies in children. Some of this research has already resulted in changes in public policy and clinical practice, for example in the case of codeine use by mothers and children. It is likely that the use of pharmacogenomics to enhance drug safety will first be realized among selected groups of children with high rates of drug use such as children with cancer, but it also likely that this research will be extended to other groups of children who have high rates of drug utilization and as well as providing insights into the mechanisms and pathophysiology of adverse drug reactions in children.

Current practices regarding codeine administration among pediatricians and pediatric subspecialists

Pharmacogenomic studies have revealed a wide variation in the metabolism of codeine to its active metabolite, morphine. A particular subset of patients, known as ultrarapid metabolizers, possesses multiple copies of the CYP2D6 gene responsible for codeine metabolism. This has been linked to serious morbidity and mortality in pediatric patients leading to considerable debate regarding the use of codeine for analgesia in the pediatric population. The current study surveyed the current practice of codeine prescription in pediatric health care providers from a single tertiary care pediatric hospital. Of the 298 responders, 43.3% (129 of 298) continue to prescribe codeine for pain management in children. The vast majority of codeine prescribers were primary health care providers (89.1%). Most of the primary care practitioners were in office-based (42.6%) or hospital-based (45.7%) group practices. There was no significant difference in codeine use based on years of experience. Given the risks associated with this practice, increased education targeting this group appears warranted.

Pharmacogenomics and pharmacoepigenomics in pediatric medicine

In the past several years, human genetics studies have progressed from monogenic to complex and common diseases because of the advancement in technologies. There is increased knowledge of the pharmacokinetics and pharmacogenomics of the drugs in adults as well as in children. These technological developments provided new diagnostic, prognostic, and therapeutic opportunities. We are now in a position to address many additional ambitious questions. For instance, in clinical medicine, interindividual variation in drug response is a major problem. Some of the heterogeneity of drug safety and efficacy among individuals can be explained by pharmacogenomics. It has also the potential to improve the treatment in both adults and children. In pediatrics however, there is ontogeny and metabolic capacity in children is different compared to adults. Several specific developmental changes may underlie some of the variability in drug response seen in children. They may also be responsible for adverse drug reactions (ADRs). Therefore, much of the diversity in drug effects cannot be explained by studying the genomic diversity alone. It is necessary to include the effect of growth (involves variations in gene expression) along with genetic differences when explaining the variability in treatment response. In this respect epigenomics may expand the scope of pharmacogenomics towards optimization of drug therapy. Future studies must focus on periods of maturation of the drug-metabolizing enzymes and polymorphisms in their genes by using candidate gene approach, gene expression analysis, genome-wide haplotype mapping, and proteomics. The integration of genetic data and clinical phenotypes along with the role of other factors is necessary to evaluate both efficacy and ADRs of any drug. It may require extensive genetic epidemiological studies spanning over many years.

Pharmacogenomics in children

Historically genetics has not been considered when prescribing drugs for children. However, it is clear that genetics are not only an important determinant of disease in children but also of drug response for many important drugs that are core agents used in the therapy of common problems in children. Advances in therapy and in the ethical construct of children's research have made pharmacogenomic assessment for children much easier to pursue. It is likely that pharmacogenomics will become part of the therapeutic decision making process for children, notably in areas such as childhood cancer where the benefits and risks of therapy are considerable.

A clinical tool for reducing central nervous system depression among neonates exposed to codeine through breast milk

Background

Neonates are commonly exposed to maternal codeine through breast milk. Central Nervous System (CNS) depression has been reported in up to 24% of nurslings following codeine exposure. In 2009, we developed guidelines to improve the safety of codeine use during breastfeeding based on previously established pharmacogenetic and clinical risk factors. The primary objective of this study was to prospectively evaluate the effectiveness of these guidelines in ensuring neonatal safety.

Methods and Findings

Women taking codeine for pain following caesarean section were given safety guidelines, including advice to use the lowest codeine dose for no longer than four days and to switch to a non-opioid when possible. Mothers provided a saliva sample for analysis of genes involved in opioid disposition, metabolism and response. A total of 238 consenting women participated. Neonatal sedation was reported in 2.1% (5/238) of breastfeeding women taking codeine according to our safety guidelines. This rate was eight fold lower than that reported in previous prospective studies. Women reporting sedated infants were taking codeine for a significantly longer period of time (4.80±2.59 days vs. 2.52±1.58 days, p = 0.0018). While following the codeine safety guidelines, mothers were less likely to supplement with formula, reported lower rates of sedation in themselves and breastfed more frequently throughout the day when compared to previously reported rates. Genotyping analysis of cytochrome p450 2D6 (CYP2D6), uridine-diphosphate glucuronosyltransferase (UGT) 2B7, p-glycoprotein (ABCB1), the mu-opioid receptor (OPRM1) and catechol-o-demethyltransferase (COMT) did not predict codeine response in breastfeeding mother/infant pairs when following the safety guidelines.

Conclusions

The only cases of CNS depression occurred when the length of codeine use exceeded the guideline recommendations. Neonatal safety of codeine can be improved using evidence-based guidelines, even in those deemed by genetics to be at high risk for toxicity.

Parent satisfaction with acute pediatric pain treatment at home

OBJECTIVES

Outpatient pain management after acute injuries is an important part of emergency department (ED) care, but there is little evidence to support best practice. Satisfaction with care is one way to assess the effectiveness of current practice. This study describes the outpatient pain experience for children with an arm fracture and explores the variables associated with parents' dissatisfaction with pain treatment for 2 analgesics after ED care.

METHODS

As a part of a randomized clinical trial assessing pain treatment after an arm fracture, parents and their children completed daily diaries recording pain scores, function disruption (play, school, sleep, eating), and adverse effects for 3 days after discharge from the ED. Parents and children also completed the Total Quality Pain Management Instrument on the third day to assess pain experience. Parents' satisfaction was defined with an arm fracture lowest reported satisfaction during the study period.

RESULTS

A total of 244 children with complete diaries were analyzed. More than half of children reported pain at home that was present "all the time" or "quite a bit." Thirty-two percent of parents were not satisfied with home pain treatment for their child. Parents' dissatisfaction was strongly associated with inadequate pain relief. It was also independently associated with nausea, disruption in play and sleep, and increased doses of medication.

DISCUSSION

Children with arm fractures experience noteworthy pain in the outpatient setting. Parents' dissatisfaction with home pain management for children suggests that more research is needed to evaluate the factors that result in improvements in both parent and child satisfaction and the most effective way of producing those changes.

Technical report: Ethical and policy issues in genetic testing and screening of children

The genetic testing and genetic screening of children are commonplace. Decisions about whether to offer genetic testing and screening should be driven by the best interest of the child. The growing literature on the psychosocial and clinical effects of such testing and screening can help inform best practices. This technical report provides ethical justification and empirical data in support of the proposed policy recommendations regarding such practices in a myriad of settings.

Apnea and oxygen desaturations in children treated with opioids after adenotonsillectomy for obstructive sleep apnea syndrome: a prospective pilot study

BACKGROUND

Recent case reports have alerted the medical community of fatality in children receiving codeine after tonsillectomy and/or adenoidectomy for obstructive sleep apnea syndrome.

OBJECTIVE

The objective of this study was to compare the rates of oxygen desaturation before and after adenotonsillectomy in children with obstructive sleep apnea syndrome (OSAS), and to examine the relationship between cytochrome P450 2D6 (CYP2D6) genotype and respiratory events.

STUDY DESIGN

This was a prospective observational study.

METHODS

Twenty-six children with OSAS (mean age 78 months, range 1.8-17 years) who underwent adenotonsillectomy were studied. CYP2D6 genotype was characterized in 21 of these children. The primary endpoints of the study were the change in the rate of desaturation and in the nadir oxygen saturation values before and in the first 24 hours after surgery as measured by pulse oximetry.

RESULTS

Twenty-two children received codeine and four were managed with hydrocodone. There was no post-operative improvement in the mean rate of desaturation (1.84 ± 1.45/hour pre-operative vs 2.97 ± 3.3/hour post-operative; p = 0.119; 95% CI -2.56, 0.313), or the post-operative nadir of oxygen saturation (85.2 ± 5.8% pre-operative vs 84.0 ± 6.8% post-operative; p = 0.632; 95% CI -3.00, 4.84) on the night after surgery. Prior to surgery, six children had an oxygen saturation nadir <80%, while post-surgery, the number increased to eight children. Ten children improved their parameters after surgery. CYP2D6 genotype by itself did not predict the changes in desaturation or nadir.

CONCLUSION

Post-operative use of opioids following OSAS may not be safe for all children. It is conceivable that if the child is among the significant proportion that experiences increased oxygen desaturations, the CNS depressing effects of codeine or hydrocodone and their respectively potent morphine or hydromorphone metabolites can further compromise respiratory drive. Larger studies are needed to investigate the potential contribution of CYP2D6 genotype.

Clinical Application of Pharmacogenomics

The purpose of this review is to discuss the clinical application of pharmacogenomics for select drug therapies (eg, proton pump inhibitors [PPIs], codeine, and carbamazepine) and to highlight limitations and challenges that preclude implementation of pharmacogenomics into clinical practice. Genetic polymorphisms of cytochrome P450 (CYP) enzymes and the presence of the human leukocyte antigen ( HLA) -B*1502 allele influence drug disposition and/or response. A portion of PPI pharmacokinetic and pharmacodynamic variability can be explained by CYP2C19 genotype. However, conflicting evidence exists related to Helicobacter pylori cure rates based on CYP2C19 genotype. For codeine, adverse drug reactions in neonates through breast-feeding from CYP2D6 ultra-rapid metabolizers have been reported. However, there is lack of conclusive evidence regarding the overall influence of CYP2D6 polymorphisms on codeine efficacy and toxicity. Although CYP2C19 and CYP2D6 genotyping tests are available, clinical utility remains low. The presence of the HLA-B*1502 allele is associated with carbamazepine-induced Stevens-Johnson syndrome (SJS) and/or toxic epidermal necrolysis (TEN). Pharmacogenomic testing is required prior to initiating carbamazepine in high-risk patients. Lack of sufficient resources, provider knowledge, and ethical, legal, and social issues are several limitations and challenges to implementing pharmacogenomic testing in clinical practice.

Pharmacogenomics of codeine, morphine, and morphine-6-glucuronide: model-based analysis of the influence of CYP2D6 activity, UGT2B7 activity, renal impairment, and CYP3A4 inhibition

BACKGROUND AND OBJECTIVE

The analgesic effect of codeine depends on the formation of the opioid metabolites morphine and morphine-6-glucuronide. Different factors have been shown or suspected to affect the safety and efficacy of codeine treatment. The objective of the current study is to assess and quantify the impact of important pharmacokinetic factors, using a mechanistic modeling approach.

METHODS

By means of a generic modeling approach integrating prior physiologic knowledge, we systematically investigated the complex dependence of opioid exposure on cytochrome P450 2D6 and 3A4 (CYP2D6 and CYP3A4), and uridine diphosphate glucuronosyltransferase 2B7 (UGT2B7) activity, as well as renal function, by means of a virtual clinical trial.

RESULTS

First, the known dominant role of CYP2D6 activity for morphine exposure was reproduced. Second, the model demonstrated that mild and moderate renal impairment and co-administration of CYP3A4 inhibitors have only minor influences on opioid exposure. Third, the model showed - in contrast to current opinion - that increased UGT2B7 activity is associated with a decrease in active opioid exposure.

CONCLUSION

Overall, the model-based analysis predicts a wide range of morphine levels after codeine administration and supports recent doubts about safe and efficacious use of codeine for analgesia in non-genotyped individuals.

More codeine fatalities after tonsillectomy in North American children

In 2009 we reported the fatal case of a toddler who had received codeine after adenotonsillectomy for obstructive sleep apnea syndrome. The child was an ultra-rapid metabolizer of cytochrome P4502D6 (CYP2D6). We now report 3 additional fatal or life-threatening cases from North America. In the 2 fatal cases, functional gene duplications encoding for CYP2D6 caused a significantly greater production of potent morphine from its parent drug, codeine. A severe case of respiratory depression in an extensive metabolizer is also noted. These cases demonstrate that analgesia with codeine or other opioids that use the CYP2D6 pathway after adenotonsillectomy may not be safe in young children with obstructive sleep apnea syndrome.

SOGC clinical practice guidelines: Substance use in pregnancy: no. 256, April 2011

OBJECTIVE

To improve awareness and knowledge of problematic substance use in pregnancy and to provide evidence-based recommendations for the management of this challenging clinical issue for all health care providers.

OPTIONS

This guideline reviews the use of screening tools, general approach to care, and recommendations for clinical management of problematic substance use in pregnancy.

OUTCOMES

Evidence-based recommendations for screening and management of problematic substance use during pregnancy and lactation.

EVIDENCE

Medline, PubMed, CINAHL, and The Cochrane Library were searched for articles published from 1950 using the following key words: substance-related disorders, mass screening, pregnancy complications, pregnancy, prenatal care, cocaine, cannabis, methadone, opioid, tobacco, nicotine, solvents, hallucinogens, and amphetamines. Results were initially restricted to systematic reviews and randomized control trials/controlled clinical trials. A subsequent search for observational studies was also conducted because there are few RCTs in this field of study. Articles were restricted to human studies published in English. Additional articles were located by hand searching through article reference lists. Searches were updated on a regular basis and incorporated in the guideline up to December 2009. Grey (unpublished) literature was also identified through searching the websites of health technology assessment and health technology assessment-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies.

VALUES

The quality of evidence was rated using the criteria described in the Report of the Canadian Task Force on the Preventive Health Care. Recommendations for practice were ranked according to the method described in that report (Table 1).

BENEFITS, HARMS, AND COSTS

This guideline is intended to increase the knowledge and comfort level of health care providers caring for pregnant women who have substance use disorders. Improved access to health care and assistance with appropriate addiction care leads to reduced health care costs and decreased maternal and neonatal morbidity and mortality.

Analgesic prescribing practices can be improved by low-cost point-of-care decision support

CONTEXT

Codeine has become a controversial choice for analgesia in children compared with other commonly available drugs.

OBJECTIVES

To evaluate whether an educational campaign shifted resident prescribing patterns away from codeine toward more appropriate analgesics.

METHODS

Our intervention consisted of a pocket-sized reference card given to all trainees and key staff in an inpatient pediatric acute care unit; pediatrics residents also had the option to attend a one-hour lecture. The pocket card recommended against codeine (including rationale) and gave prescription guidance for our institution's preferred formulary alternative analgesics, which include tramadol and hydrocodone. We used inpatient prescribing data to track the prescribing of codeine and alternative medications over time.

RESULTS

Following the interventions, there was a significant decrease in the percentage of patients receiving codeine (13.5% of patients received the drug in the year before, 5.4% in the year after, P < 0.0001). Use of hydrocodone-containing analgesics increased overall during the same period (7.4%-16%, P < 0.0001) as did tramadol use (0.2%-2.6%, P < 0.0001). There were no changes in pain management satisfaction scores.

CONCLUSION

A simple low-cost educational campaign consisting primarily of a pocket guide to analgesics markedly improved analgesic prescribing patterns, and that improvement extended to services not targeted by the didactic component of our educational campaign. Point-of-care decision support by means of a pocket card may be sufficient for effecting change in medication prescribing patterns of trainees.

Substance use in pregnancy

OBJECTIVE

To improve awareness and knowledge of problematic substance use in pregnancy and to provide evidence-based recommendations for the management of this challenging clinical issue for all health care providers.

OPTIONS

This guideline reviews the use of screening tools, general approach to care, and recommendations for clinical management of problematic substance use in pregnancy.

OUTCOMES

Evidence-based recommendations for screening and management of problematic substance use during pregnancy and lactation.

EVIDENCE

Medline, PubMed, CINAHL, and The Cochrane Library were searched for articles published from 1950 using the following key words: substance-related disorders, mass screening, pregnancy complications, pregnancy, prenatal care, cocaine, cannabis, methadone, opioid, tobacco, nicotine, solvents, hallucinogens, and amphetamines. Results were initially restricted to systematic reviews and randomized control trials/controlled clinical trials. A subsequent search for observational studies was also conducted because there are few RCTs in this field of study. Articles were restricted to human studies published in English. Additional articles were located by hand searching through article reference lists. Searches were updated on a regular basis and incorporated in the guideline up to December 2009. Grey (unpublished) literature was also identified through searching the websites of health technology assessment and health technology assessment-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies.

VALUES

The quality of evidence was rated using the criteria described in the Report of the Canadian Task Force on the Preventive Health Care. Recommendations for practice were ranked according to the method described in that report (Table 1).

BENEFITS, HARMS, AND COSTS

This guideline is intended to increase the knowledge and comfort level of health care providers caring for pregnant women who have substance use disorders. Improved access to health care and assistance with appropriate addiction care leads to reduced health care costs and decreased maternal and neonatal morbidity and mortality.

RECOMMENDATIONS

1. All pregnant women and women of childbearing age should be screened periodically for alcohol, tobacco, and prescription and illicit drug use. (III-A) 2. When testing for substance use is clinically indicated, urine drug screening is the preferred method. (II-2A) Informed consent should be obtained from the woman before maternal drug toxicology testing is ordered. (III-B) 3. Policies and legal requirements with respect to drug testing of newborns may vary by jurisdiction, and caregivers should be familiar with the regulations in their region. (III-A) 4. Health care providers should employ a flexible approach to the care of women who have substance use problems, and they should encourage the use of all available community resources. (II-2B) 5. Women should be counselled about the risks of periconception, antepartum, and postpartum drug use. (III-B) 6. Smoking cessation counselling should be considered as a first-line intervention for pregnant smokers. (I-A) Nicotine replacement therapy and/or pharmacotherapy can be considered if counselling is not successful. (I-A) 7. Methadone maintenance treatment should be standard of care for opioid-dependent women during pregnancy. (II-IA) Other slow-release opioid preparations may be considered if methadone is not available. (II-2B) 8. Opioid detoxification should be reserved for selected women because of the high risk of relapse to opioids. (II-2B) 9. Opiate-dependent women should be informed that neonates exposed to heroin, prescription opioids, methadone, or buprenorphine during pregnancy are monitored closely for symptoms and signs of neonatal withdrawal (neonatal abstinence syndrome). (II-2B) Hospitals providing obstetric care should develop a protocol for assessment and management of neonates exposed to opiates during pregnancy. (III-B) 10. Antenatal planning for intrapartum and postpartum analgesia may be offered for all women in consultation with appropriate health care providers. (III-B) 11. The risks and benefits of breastfeeding should be weighed on an individual basis because methadone maintenance therapy is not a contraindication to breastfeeding. (II-3B).