Codeine intoxication associated with ultrarapid CYP2D6 metabolism

Pharmacogenomics of Drug Metabolizing Enzymes and Transporters: Relevance to Precision Medicine

The interindividual genetic variations in drug metabolizing enzymes and transporters influence the efficacy and toxicity of numerous drugs. As a fundamental element in precision medicine, pharmacogenomics, the study of responses of individuals to medication based on their genomic information, enables the evaluation of some specific genetic variants responsible for an individual’s particular drug response. In this article, we review the contributions of genetic polymorphisms to major individual variations in drug pharmacotherapy, focusing specifically on the pharmacogenomics of phase-I drug metabolizing enzymes and transporters. Substantial frequency differences in key variants of drug metabolizing enzymes and transporters, as well as their possible functional consequences, have also been discussed across geographic regions. The current effort illustrates the common presence of variability in drug responses among individuals and across all geographic regions. This information will aid health-care professionals in prescribing the most appropriate treatment aimed at achieving the best possible beneficial outcomes while avoiding unwanted effects for a particular patient.

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.

The impact of codeine re-scheduling on misuse: a retrospective review of calls to Australia's largest poisons centre

BACKGROUND AND AIMS

Codeine is the most commonly used opioid in the world, and is available over the counter (OTC) in many countries, including Australia. Several countries are reconsidering codeine's OTC status due to concerns over addiction and misuse, with serious morbidity and mortality being reported. Australia's Therapeutic Goods Administration restricted codeine containing analgesics to 'Pharmacist Only' in 2010, and has recently been considering further up-scheduling to make codeine 'Prescription Only'. This paper estimated Australian trends of codeine misuse over the past 12 years, and examined whether trends changed following previous rescheduling efforts in 2010.

DESIGN

A retrospective review of calls regarding codeine misuse made to the New South Wales Poisons Information Centre (NSWPIC, Australia's largest poisons centre), 2004-15. Joinpoint software was used to quantify the average annual change in calls, and whether there was a significant change in trend at any time, including following rescheduling.

SETTING

Australia.

PARTICIPANTS

Four hundred patients about whom a call was made to the NSWPIC.

MEASURES

Calls per year, patient age, gender, tablets taken per day, formulation used, symptom disposition.

FINDINGS

The NSWPIC database contained 400 cases of codeine combination analgesic misuse from 2004 to 2015. Joinpoint analysis showed that the frequency of cases increased significantly from 2004 to 2015, with an average annual percentage change (AAPC) of 19.5% [95% confidence interval (CI) = 13.8-25.5% P < 0.0001] for paracetamol/codeine and 17.9% (95% CI = 7.9-28.9%, P < 0.01) for ibuprofen/codeine. No significant change in trend was seen at any time, including following 2010 rescheduling. The median age of patients was 34 and 27 years for paracetamol/codeine and ibuprofen/codeine cases, respectively. Gender distribution was approximately equal. Clinical features reported were consistent with codeine, paracetamol and ibuprofen toxicity.

CONCLUSIONS

Misuse of codeine combination products appears to be increasing in Australia. Limited rescheduling in 2010 failed to curb this increase.

Comprehensive evidence-based review on European antitussives

Acute cough caused by viral respiratory tract infections is probably the most common illness to afflict mankind. Despite the widespread but ineffective prescribing of antibiotics, there is no specific therapy. Home remedies and over-the-counter medicines are the mainstay for treatment of this short-lived but debilitating condition where cough is a major troublesome symptom. Across Europe, there are large variations in the recommendations made by healthcare professionals for the treatment of acute cough. This has arisen through custom and practice based on the evidence of historical studies performed to standards well short of what would be considered legitimate today. Acute cough is particularly difficult to study in a controlled setting because of the high rate of spontaneous remission and a large placebo effect. Here we detail the validated modern methodology used to assess the efficacy of antitussives and review the drugs commonly used in Europe against these standards.

The role of cytochrome P450 pharmacogenomics in chronic non-cancer pain patients

INTRODUCTION

Pharmacogenomics is the field that studies an individualized treatment approach for patients' medication regimen that can impact drug safety, productivity, and personalized health care. Pharmacogenomics characterizes the genetic differences in metabolic pathways which can affect a patient's individual responses to drug treatments. Areas covered: The various responses to pharmacological agents are mainly determined by the different types of genetic variants of the CYP450. CYP2D6 polymorphism is well known for its variation in the metabolism of drugs from many therapeutic arenas, including some analgesic drugs such as codeine, hydromorphone, oxycodone and tramadol. Allele combinations determine the phenotypic expression, characterized as either: extensive metabolizer, intermediate metabolizer, ultra-rapid metabolizer and poor metabolizer. Expert opinion: The Human Genome Project (HGP) revolutionized the future of medicine and the way health care providers approach individualized patient treatment, and chronic pain management is one of those areas. The key findings in the literature appear to be related to the CYP2D6 expression and its high polymorphism influencing the metabolism of opioid medications, and the impact of that on the patient's therapeutic outcome thus exemplifying the importance of genetic testing for CYP2D6 in the process of physician therapeutic decision making.

An Analysis of 34,218 Pediatric Outpatient Controlled Substance Prescriptions

BACKGROUND

Prescription errors are among the most common types of iatrogenic errors. Because of a previously reported 82% error rate in handwritten discharge narcotic prescriptions, we developed a computerized, web-based, controlled substance prescription writer that includes weight-based dosing logic and alerts to reduce the error rate to (virtually) zero. Over the past 7 years, >34,000 prescriptions have been created by hospital providers using this platform. We sought to determine the ongoing efficacy of the program in prescription error reduction and the patterns with which providers prescribe controlled substances for children and young adults (ages 0-21 years) at hospital discharge.

METHODS

We examined a database of 34,218 controlled substance discharge prescriptions written by our institutional providers from January 1, 2007 to February 14, 2014, for demographic information, including age and weight, type of medication prescribed based on patient age, formulation of dispensed medication, and amount of drug to be dispensed at hospital discharge. In addition, we randomly regenerated 2% (700) of prescriptions based on stored data and analyzed them for errors using previously established error criteria. Weights that were manually entered into the prescription writer by the prescriber were compared with the patient's weight in the hospital's electronic medical record.

RESULTS

Patients in the database averaged 9 ± 6.1 (range, 0-21) years of age and 36.7 ± 24.9 (1-195) kg. Regardless of age, the most commonly prescribed opioid was oxycodone (73%), which was prescribed as a single agent uncombined with acetaminophen. Codeine was prescribed to 7% of patients and always in a formulation containing acetaminophen. Liquid formulations were prescribed to 98% of children <6 years of age and to 16% of children >12 years of age (the remaining 84% received tablet formulations). Regardless of opioid prescribed, the amount of liquid dispensed averaged 106 ± 125 (range, 2-3240) mL, and the number of tablets dispensed averaged 51 ± 51 (range, 1-1080). Of the subset of 700 regenerated prescriptions, all were legible (drug, amount dispensed, dose, patient demographics, and provider name) and used best prescribing practice (e.g., no trailing zero after a decimal point, leading zero for doses <1). Twenty-five of the 700 (3.6%) had incorrectly entered weights compared with the most recent weight in the chart. Of these, 14 varied by 10% or less and only 2 varied by >15%. Of these, 1 resulted in underdosing (true weight 80 kg prescribed for a weight of 50 kg) and the other in overdosing (true weight 10 kg prescribed for a weight of 30 kg).

CONCLUSIONS

A computerized prescription writer eliminated most but not all the errors common to handwritten prescriptions. Oxycodone has supplanted codeine as the most commonly prescribed oral opioid in current pediatric pain practice and, independent of formulation, is dispensed in large quantities. This study underscores the need for liquid opioid formulations in the pediatric population and, because of their abuse potential, the urgent need to determine how much of the prescribed medication is actually used by patients.

Pharmacogenetics for Safe Codeine Use in Sickle Cell Disease

After postoperative deaths in children who were prescribed codeine, several pediatric hospitals have removed it from their formularies. These deaths were attributed to atypical cytochrome P450 2D6 (CYP2D6) pharmacogenetics, which is also implicated in poor analgesic response. Because codeine is often prescribed to patients with sickle cell disease and is now the only Schedule III opioid analgesic in the United States, we implemented a precision medicine approach to safely maintain codeine as an option for pain control. Here we describe the implementation of pharmacogenetics-based codeine prescribing that accounts for CYP2D6 metabolizer status. Clinical decision support was implemented within the electronic health record to guide prescribing of codeine with the goal of preventing its use after tonsillectomy or adenoidectomy and in CYP2D6 ultra-rapid and poor metabolizer (high-risk) genotypes. As of June 2015, CYP2D6 genotype results had been reported for 2468 unique patients. Of the 830 patients with sickle cell disease, 621 (75%) had a CYP2D6 genotype result; 7.1% were ultra-rapid or possible ultra-rapid metabolizers, and 1.4% were poor metabolizers. Interruptive alerts recommended against codeine for patients with high-risk CYP2D6 status. None of the patients with an ultra-rapid or poor metabolizer genotype were prescribed codeine. Using genetics to tailor analgesic prescribing retained an important therapeutic option by limiting codeine use to patients who could safely receive and benefit from it. Our efforts represent an evidence-based, innovative medication safety strategy to prevent adverse drug events, which is a model for the use of pharmacogenetics to optimize drug therapy in specialized pediatric populations.

The Use of a Pediatric Migraine Practice Guideline in an Emergency Department Setting

OBJECTIVE

The aim of the study was to evaluate the safety and efficacy of a standardized pediatric migraine practice guideline in the emergency department (ED).

METHODS

Migraine Clinical Practice Guideline (MCPG) was created in collaboration with the Division of Pediatric Neurology and Pediatric Emergency Medicine. The MCPG was established on evidence-based data and best practice after a review of the literature. The MCPG was implemented for patients with a known diagnosis of migraine headaches and a verbal numeric pain score (VPS) greater than 6 on a 0 to 10 scale. Patients received intravenous saline, ketorolac, diphenhydramine, and either metoclopramide or prochlorperazine. After 40 minutes, another VPS was obtained, and if no improvement, a repeat dose of metoclopramide or prochlorperazine was administered. If after 40 minutes and minimal pain relief occurred, a consult to neurology was made. A chart review of patients enrolled in the MCPG from April 2004 to April 2013 was conducted. We recorded demographic data, vital signs, ED length of stay, initial VPS, last recorded VPS, adverse events, and admission rate. Nonparametric statistics were performed.

RESULTS

A total of 533 charts were identified with a discharge diagnosis of migraine headache of which 266 were enrolled in the MCPG (179 females and 87 males). Mean (SD) age was 13.9 (3.1). Mean (SD) initial VPS was 7.8 (2.0). Mean (SD) discharge VPS was 2.1 (2.8), representing a 73% reduction of pain. Twenty patients (7.5%) were admitted for status migrainosus; mean (SD) age was 14.0 (3.5) years and mean (SD) VPS was 6.3 (2.8). Mean (SD) length of stay in ED was 283 (107) minutes. No adverse events were identified.

CONCLUSIONS

Our MCPG was clinically safe and effective in treating children with acute migraine headaches. Our data add to the dearth of existing published literature on migraine treatment protocols in the ED setting. We recommend additional prospective and comparative studies to further evaluate the effectiveness of our protocol in this patient population.

Guidelines for Monitoring and Management of Pediatric Patients Before, During, and After Sedation for Diagnostic and Therapeutic Procedures: Update 2016

The safe sedation of children for procedures requires a systematic approach that includes the following: no administration of sedating medication without the safety net of medical/dental supervision, careful presedation evaluation for underlying medical or surgical conditions that would place the child at increased risk from sedating medications, appropriate fasting for elective procedures and a balance between the depth of sedation and risk for those who are unable to fast because of the urgent nature of the procedure, a focused airway examination for large (kissing) tonsils or anatomic airway abnormalities that might increase the potential for airway obstruction, a clear understanding of the medication's pharmacokinetic and pharmacodynamic effects and drug interactions, appropriate training and skills in airway management to allow rescue of the patient, age- and size-appropriate equipment for airway management and venous access, appropriate medications and reversal agents, sufficient numbers of staff to both carry out the procedure and monitor the patient, appropriate physiologic monitoring during and after the procedure, a properly equipped and staffed recovery area, recovery to the presedation level of consciousness before discharge from medical/dental supervision, and appropriate discharge instructions. This report was developed through a collaborative effort of the American Academy of Pediatrics and the American Academy of Pediatric Dentistry to offer pediatric providers updated information and guidance in delivering safe sedation to children.

Clinical Utility and Economic Impact of CYP2D6 Genotyping

Pharmacogenetics examines an individual's genetic makeup to help predict the safety and efficacy of medications. Practical application optimizes treatment selection to decrease the failure rate of medications and improve clinical outcomes. Lack of efficacy is costly due to adverse drug reactions and increased hospital stays. Cytochrome P450 2D6 (CYP2D6) metabolizes roughly 25% of all drugs. Detecting variants that cause altered CYP2D6 enzymatic activity identifies patients at risk of adverse drug reactions or therapeutic failure with standard dosages of medications metabolized by CYP2D6. This article discusses the clinical application of pharmacogenetics to improve care and decrease costs.

High frequency of CYP2D6 ultrarapid metabolizer genotypes in an Ashkenazi Jewish population from Argentina

A twofold higher frequency of CYP2D6 ultrarapid metabolizers (estimated from genotype: gUMs) was reported among Ashkenazi Jews (AJ) living in New York (USA) than in other North American Caucasians, which might be important to guide the prescription for CYP2D6 substrates in AJ communities around the world. This study was aimed to determine whether the high frequency of CYP2D6 gUMs described in AJ from USA was replicated in AJ from Argentina when compared with other multiethnic admixture Argentines (GA). The frequency of the most common allelic variants and of CYP2D6 gUMs (>2 active genes) and poor metabolizers (0 active genes, gPMs) was also compared among the studied Argentine populations. CYP2D6 genotyping was performed in 173 AJ and 246 GA DNA samples of unrelated donors from the metropolitan area of Buenos Aires. CYP2D6 alleles (*2, *3, *4, *5, *6, *10, *17, *35, *41 and multiple copies), genotypes and functional phenotype frequencies were determined. The frequencies of gUMs and gPMs in AJ from Argentina were 11.5% and 5.2%, respectively, whereas in GA, the frequencies of gUM and gPMs were 6.5% and 4.9%, respectively. Comparisons between AJ and GA showed that gUMs frequencies were twofold higher (P<0.05) in AJ than GA. CYP2D6*35 allele was more frequent in GA than AJ, whereas CYP2D6*41 and *1xN were more frequent in AJ than in GA (P<0.05). This study supports the previously reported high frequency of gUMs on another Ashkenazi population in New York. The present findings also support the interethnic variability of CYP2D6 genetic polymorphism in the overall Argentine population.

Impact of a personal CYP2D6 testing workshop on physician assistant student attitudes toward pharmacogenetics

AIM

We assessed the impact of personal CYP2D6 testing on physician assistant student competency in, and attitudes toward, pharmacogenetics (PGx).

MATERIALS & METHODS

Buccal samples were genotyped for CYP2D6 polymorphisms. Results were discussed during a 3-h PGx workshop. PGx knowledge was assessed by pre- and post-tests. Focus groups assessed the impact of the workshop on attitudes toward the clinical utility of PGx.

RESULTS

Both student knowledge of PGx, and its perceived clinical utility, increased immediately following the workshop. However, exposure to PGx on clinical rotations following the workshop seemed to influence student attitudes toward PGx utility.

CONCLUSION

Personal CYP2D6 testing improves both knowledge and comfort with PGx. Continued exposure to PGx concepts is important for transfer of learning.

Pharmacogenetics of drug-metabolizing enzymes in US Hispanics

Although the Hispanic population is continuously growing in the United States, they are underrepresented in pharmacogenetic studies. This review addresses the need for compiling available pharmacogenetic data in US Hispanics, discussing the prevalence of clinically relevant polymorphisms in pharmacogenes encoding for drug-metabolizing enzymes. CYP3A5*3 (0.245-0.867) showed the largest frequency in a US Hispanic population. A higher prevalence of CYP2C9*3, CYP2C19*4, and UGT2B7 IVS1+985 A>G was observed in US Hispanic vs. non-Hispanic populations. We found interethnic and intraethnic variability in frequencies of genetic polymorphisms for metabolizing enzymes, which highlights the need to define the ancestries of participants in pharmacogenetic studies. New approaches should be integrated in experimental designs to gain knowledge about the clinical relevance of the unique combination of genetic variants occurring in this admixed population. Ethnic subgroups in the US Hispanic population may harbor variants that might be part of multiple causative loci or in linkage-disequilibrium with functional variants. Pharmacogenetic studies in Hispanics should not be limited to ascertain commonly studied polymorphisms that were originally identified in their parental populations. The success of the Personalized Medicine paradigm will depend on recognizing genetic diversity between and within US Hispanics and the uniqueness of their genetic backgrounds.

Anesthesiological considerations for children with obstructive sleep apnea

PURPOSE OF REVIEW

To summarize recent evidence-based data regarding outcomes associated with children who have obstructive sleep apnea (OSA).

RECENT FINDINGS

Internet surveys conducted by pediatric otolaryngologists and pediatric anesthesiologists have reported a disturbing number of deaths within 24 h of tonsillectomy attributed to postsurgical/anesthesia apnea. Several occurred in the post anesthesia care unit after routine monitors had been removed. In addition, a number of deaths also have been attributed to children who have duplicated cytochromes allowing the rapid conversion of codeine to morphine, thus producing a relative drug overdose. Finally, there is some human and animal evidence suggesting that repeated episodes of hypoxemia result in altered opioid receptors causing relative opioid sensitivity. These factors have important clinical implications.

SUMMARY

Perioperative deaths in children with OSA occur at a low frequency. Hypoxia-induced opioid sensitivity combined with an approximate 1-2% incidence of rapid conversion of codeine to morphine suggest the need for new approaches for providing preoperative assessment of risk, extended postoperative observation and the need for alternative opioids to codeine. Additionally, new less painful surgical approaches may help to reduce postoperative opioid requirements and therefore perhaps less risk for opiate-induced apnea in this vulnerable population.

The extent and correlates of community-based pharmaceutical opioid utilisation in Australia

PURPOSE

There has been concern regarding the increasing use of opioids and related harm. We present data on opioid utilisation across Australia and consider sociodemographic factors that may affect utilisation rates.

METHODS

IMS Health national sales data for over-the-counter (codeine) and prescription opioids (buprenorphine, codeine, dextropropoxyphene, fentanyl, hydromorphone, methadone, morphine, oxycodone, tapentadol and tramadol) were used to estimate total utilisation rates in the community during 2013, mapped to Statistical Local Areas (SLAs) and Remoteness Areas. All opioid amounts were measured in pack sales and milligrammes then converted to oral morphine equivalent milligrammes (OME mg) for comparison across opioids. Data on the demographic characteristics of SLAs were obtained from the ABS (sex and age distribution, income and levels of physical labour) and other sources (number of pharmacies in SLAs) and were included in linear regression analyses.

RESULTS

In 2013, an estimated 10 747 kg (OME) of opioids were sold across Australia, equating to 481 OME mg per person. There was considerable geographic variation in opioid utilisation, with higher rates of use in rural and regional areas. Geographic areas that were less populated, had more men and older people, proportionally more low-income earning households and greater proportions in jobs requiring physical labour had higher utilisation rates.

CONCLUSIONS

Substantial geographic variation in opioid utilisation was identified, with areas outside of major cities having higher rates of utilisation of all types of opioids. Prescription monitoring and best practice interventions aimed at improving opioid use need to have a particular focus on areas outside of major cities. Copyright © 2016 John Wiley & Sons, Ltd.

Mass Spectrometry in Precision Medicine: Phenotypic Measurements Alongside Pharmacogenomics

BACKGROUND

Precision medicine is becoming a major topic within the medical community and is gaining traction as a standard approach in many disciplines. This approach typically revolves around the use of a patient's genetic makeup to allow the physician to choose the appropriate course of treatment. In many cases the genetic information directs the drug to be used to treat the patient. In other cases the genetic markers associated with enzyme function may inform dosage recommendations. However there is a second way in which precision medicine can be practiced—that is, by therapeutic drug monitoring (TDM).

CONTENT

A review of the use of mass spectrometry for TDM in the arena of precision medicine is undertaken. Because the measurement of a drug or its metabolites provides the physician with a snapshot of the therapeutic exposure the patient is undergoing, these concentrations can be thought of as an actual phenotype measurement based around the patient's genetics coupled with all of the environmental, pharmacological, and nutritional variables. The outcome of a TDM measurement by mass spectrometry provides the patient's current phenotype vs the potential phenotype imputed by the genetics.

SUMMARY

The use of mass spectrometry can provide an understanding of how a drug is interacting with the patient, and is orthoganol to the information provided by pharmacogenomic assays. Further, the speed and relatively low expense of drug monitoring by mass spectrometry makes it an ideal test for precision medicine patient management.

Response to intravenous fentanyl infusion predicts subsequent response to transdermal fentanyl

PURPOSE

Prediction of the response to transdermal fentanyl (FENtd) before its use for chronic pain is desirable. We tested the hypothesis that the response to intravenous fentanyl infusion (FENiv) can predict the response to FENtd, including the analgesic and adverse effects.

METHODS

The study subjects were 70 consecutive patients with chronic pain. The response to fentanyl at 0.1 mg diluted in 50 ml of physiological saline and infused over 30 min was tested. This was followed by treatment with FENtd (Durotep MT patch 2.1 mg) at a dose of 12.5 µg/h for 2 weeks. Pain intensity before and after FENiv and 2 weeks after FENtd, and the response to treatment, were assessed by the numerical rating scale (NRS), clinical global impression-improvement scale (CGI-I), satisfaction scale (SS), and adverse effects.

RESULTS

The NRS score decreased significantly from 7 (4-9) [median (range)] at baseline to 3 (0-8) after FENiv (p < 0.001), and to 4 (1-8) after FENtd (p < 0.001). The effects of FENiv, as evaluated by ΔNRS, CGI-I, and SS, were significantly greater than those of FENtd (p < 0.001, each), but not by the frequency and the severity of adverse effects, with the exception of dizziness. ΔNRS, and severity of adverse effects (drowsiness, dizziness, nausea, dry mouth, and pruritus) of FENiv correlated significantly with those of FENtd (rs > 0.04, each).

CONCLUSIONS

The analgesic and side effects after intravenous fentanyl infusion can be used to predict the response to short-term transdermal treatment with fentanyl.

The pharmacogenetics of opioid therapy in the management of postpartum pain: a systematic review

AIMS

Opioids are commonly prescribed for postpartum pain. Yet, providing adequate pain relief, while ensuring that the mother and her breastfeeding infant are protected from adverse events can be challenging. The objective of this systematic review was to identify the role of opioid pharmacogenetics in analgesia and adverse events among patients being treated for postpartum pain, along with their breastfeeding infants.

METHODS

A comprehensive search of the literature was conducted in seven databases on June 3-4, 2015. Two reviewers independently screened studies for eligibility, extracted data and evaluated study quality using the Newcastle-Ottawa Scale.

RESULTS

Among the 2082 papers retrieved from the search, 17 were included in the review. These 17 papers consisted of various study designs, opioids, polymorphisms and patient outcomes. This systematic review reveals that CYP2D6, OPRM1 A118G, UGT2B7 C802T and ABCB1 G2677AT may contribute to postpartum analgesia or adverse events.

CONCLUSION

These findings may assist in personalizing care for patients receiving opioids during the postpartum period.

Opioid overdose in a child: case report and discussion with emphasis on neurosurgical implications

In environments in which opioids are increasingly abused for recreation, children are becoming more at risk for both accidental and nonaccidental intoxication. In toxic doses, opioids can cause potentially lethal acute leukoencephalopathy, which has a predilection for the cerebellum in young children. The authors present the case of a 2-year-old girl who suffered an accidental opioid overdose, presenting with altered mental status requiring cardiorespiratory support. She required emergency posterior fossa decompression, partial cerebellectomy, and CSF drainage due to cerebellar edema compressing the fourth ventricle. To the authors' knowledge, this is the first report of surgical decompression used to treat cerebellar edema associated with opioid overdose in a child.

Dihydrocodeine: safety concerns

Dihydrocodeine (DHC) is a semi-synthetic analogue of codeine, which was formed by the hydrogenation of the double tie in the main chain of the codeine molecule - instead of a double bond between carbons 7 and 8 DHC possesses a single bond. DHC is used as an analgesic and antitussive agent and for the management of dyspnea and opioid addiction. Limited data is available on the potency of DHC to other opioids. The analgesic effect of DHC is similar to codeine and approximately twice as potent as tramadol for an oral route. In contrast to codeine and tramadol, DHC analgesia seem to be irrespective of CYP2D6 activity due to parent compound analgesic effects, multiple metabolic pathways and limited role of dihydromorphine in DHC analgesia. As the drug is commonly available appropriate titration and dosing and knowledge of its metabolism and possible adverse effects are important for safe prescription of DHC.

[Drug interactions in pain therapy]

BACKGROUND

Pain is one of the most common reasons for consulting a physician. Chronic pain patients often suffer from a variety of comorbidities, such as depression and anxiety and they are therefore often simultaneously treated with more than one drug. The probability of drug interactions increases with every additional drug.

MATERIAL AND METHODS

A systematic internet and literature search up to February 2015 was carried out. Systematic lists were included. In addition, the drug prescription information sheets were used and an internet search via Pubmed and google.com was carried out for drugs alone and in combination in order to find substance-specific interactions.

RESULTS

A differentiation is made between pharmaceutical, pharmacodynamic and pharmacokinetic drug interactions. Pharmaceutical interactions are caused by chemical, physical or physicochemical incompatibility of drugs or adjuvants used. These can even occur outside the body and during concomitant administration via the same route. A pharmacodynamic interaction in pain management is for example the additive sedative effect of opioids and benzodiazepines when taken together. Pharmacokinetic interactions occur during the absorption, distribution, metabolism and in the elimination phases.

CONCLUSION

Many drug interactions can be avoided by careful and continuous evaluation of pharmacotherapy and if necessary its adaptation; however, a sound knowledge of the underlying pharmacological mechanisms and the properties of currently used analgesics is necessary.

Strategies for implementation of an effective pharmacogenomics program in pharmacy education

Sequencing of the human genome and the evidence correlating specific genetic variations to diseases have opened up the potential of genomics to more effective and less harmful interventions of human diseases. A wealth of pharmacogenomics knowledge is in place for the practice of precision medicine. However, this knowledge is not fully realized in clinical practice. One reason for this impasse is the lack of in-depth understanding of the potential of pharmacogenomics among the healthcare professionals. Pharmacists are the point-of-care providers and are expected to advise clinicians on matters relating to the implementation of pharmacogenomics in patient care. However, current pharmacogenomics instruction in pharmacy schools fails to produce pharmacists with the required knowledge or practical training in this discipline. In this perspective, we provide several strategies to overcome limitations faced by pharmacy schools. Once implemented, pharmacy schools will produce precision medicine-ready pharmacists.

Pharmacogenomics and Opioid Analgesics: Clinical Implications

Variation exists in patient response on analgesic treatment in terms of efficacy and safety. This variation may be in part explained by pharmacogenomics. This paper aimed to review data on pharmacogenomics of opioid analgesics focusing on the effect of genetic variation on the efficacy and safety of these agents. Current evidence suggests that pharmacogenomics contribute to variation in efficacy and safety of opioids. However, most data come from case control studies and case reports. In addition, a recognized drawback in the field of pharmacogenomics is the common occurrence of false positive association between polymorphisms and the investigated outcome. Prospective studies are needed to further elucidate the clinical implications of available data as well as to define the guidelines for the clinical application of pharmacogenomic data. Furthermore, basic research should focus on the identification of biologically meaningful polymorphisms enabling a hypothesis with biological plausibility driven research in the field of pharmacogenomics of analgesics. Moreover, the publication of relevant negative results should be favoured.

Combining ibuprofen and acetaminophen for acute pain management after third-molar extractions: translating clinical research to dental practice

BACKGROUND

Effective and safe drug therapy for the management of acute postoperative pain has relied on orally administered analgesics such as ibuprofen, naproxen and acetaminophen, or N-acetyl-p-aminophenol (APAP), as well as combination formulations containing opioids such as hydrocodone with APAP. The combination of ibuprofen and APAP has been advocated in the last few years as an alternative therapy for postoperative pain management. The authors conducted a critical analysis to evaluate the scientific evidence for using the ibuprofen-APAP combination and propose clinical treatment recommendations for its use in managing acute postoperative pain in dentistry.

TYPES OF STUDIES REVIEWED

The authors used quantitative evidence-based reviews published by the Cochrane Collaboration to determine the relative analgesic efficacy and safety of combining ibuprofen and APAP. They found additional articles by searching the Ovid MEDLINE, PubMed and ClinicalTrials.gov databases.

CONCLUSIONS

The results of the quantitative systematic reviews indicated that the ibuprofen-APAP combination may be a more effective analgesic, with fewer untoward effects, than are many of the currently available opioid-containing formulations. In addition, the authors found several randomized controlled trials that also indicated that the ibuprofen-APAP combination provided greater pain relief than did ibuprofen or APAP alone after third-molar extractions. The adverse effects associated with the combination were similar to those of the individual component drugs. Practical Implications. Combining ibuprofen with APAP provides dentists with an additional therapeutic strategy for managing acute postoperative dental pain. This combination has been reported to provide greater analgesia without significantly increasing the adverse effects that often are associated with opioid-containing analgesic combinations. When making stepwise recommendations for the management of acute postoperative dental pain, dentists should consider including ibuprofen-APAP combination therapy.

Individualized medicine enabled by genomics in Saudi Arabia

The biomedical research sector in Saudi Arabia has recently received special attention from the government, which is currently supporting research aimed at improving the understanding and treatment of common diseases afflicting Saudi Arabian society. To build capacity for research and training, a number of centres of excellence were established in different areas of the country. Among these, is the Centre of Excellence in Genomic Medicine Research (CEGMR) at King Abdulaziz University, Jeddah, with its internationally ranked and highly productive team performing translational research in the area of individualized medicine. Here, we present a panorama of the recent trends in different areas of biomedical research in Saudi Arabia drawing from our vision of where genomics will have maximal impact in the Kingdom of Saudi Arabia. We describe advances in a number of research areas including; congenital malformations, infertility, consanguinity and pre-implantation genetic diagnosis, cancer and genomic classifications in Saudi Arabia, epigenetic explanations of idiopathic disease, and pharmacogenomics and personalized medicine. We conclude that CEGMR will continue to play a pivotal role in advances in the field of genomics and research in this area is facing a number of challenges including generating high quality control data from Saudi population and policies for using these data need to comply with the international set up.

Personalizing medicine in geriatric oncology

Minimizing toxicity while maximizing efficacy is a common goal in the treatment of any condition but its importance is underscored in the discipline of oncology because of the serious nature of many chemotherapeutic toxicities and the risk of cancer recurrence or disease progression. The challenge of achieving an optimal therapeutic index is especially augmented in the elderly population because of age-related metabolism changes and interacting concurrent medications. Additional factors, such as germline mutations in drug-metabolizing enzymes and other pharmacogenomic alterations, may have more pronounced effects in elderly patients, given their predisposition to altered pharmacokinetics and pharmacodynamics with resulting increased risk of toxicity. Examples of the possible interplay of these factors will be discussed using tamoxifen, paclitaxel, codeine, and fluorouracil as starting points. Limited participation of the elderly in many cancer trials, especially trials assessing drug exposure, makes much knowledge on the interaction of these patient and environmental factors speculative in nature but presents an opportunity for future research to achieve better optimization of chemotherapeutic agents in the elderly.

In vitro cytochrome P450 inhibition potential of methylenedioxy-derived designer drugs studied with a two-cocktail approach

In vitro cytochrome P450 (CYP) inhibition assays are common approaches for testing the inhibition potential of drugs for predicting potential interactions. In contrast to marketed medicaments, drugs of abuse, particularly the so-called novel psychoactive substances, were not tested before distribution and consumption. Therefore, the inhibition potential of methylenedioxy-derived designer drugs (MDD) of different drug classes such as aminoindanes, amphetamines, benzofurans, cathinones, piperazines, pyrrolidinophenones, and tryptamines should be elucidated. The FDA-preferred test substrates, split in two cocktails, were incubated with pooled human liver microsomes and analysed after protein precipitation using LC-high-resolution-MS/MS. IC50 values were determined of MDD showing more than 50 % inhibition in the prescreening. Values were calculated by plotting the relative metabolite concentration formed over the logarithm of the inhibitor concentration. All MDD showed inhibition against CYP2D6 activity and most of them in the range of the clinically relevant CYP2D6 inhibitors quinidine and fluoxetine. In addition, the beta-keto compounds showed inhibition of the activity of CYP2B6, 5,6-MD-DALT of CYP1A2 and CYP3A, and MDAI of CYP2A6, all in the range of clinically relevant inhibitors. In summary, all MDD showed inhibition of the activity of CYP2D6, six of CYP1A2, three of CYP2A6, 13 of CYP2B6, two of CYP2C9, six of CYP2C19, one of CYP2E1, and six of CYP3A. These results showed that the CYP inhibition by MDD might be clinically relevant, but further studies are needed for final conclusions.

The impact of CYP2D6 polymorphisms on the pharmacokinetics of codeine and its metabolites in Mongolian Chinese subjects

PURPOSE

Codeine is an analgesic drug acting on μ-opioid receptors predominantly via its metabolite morphine formed almost exclusively by CYP2D6. Genetic polymorphisms in CYP2D6 are associated with diminished pain relief and/or severe opioid side effects. In Chinese individuals, CYP2D6*10 is the most common allele with reduced enzyme activity. In this study, we investigated the effect of this allele on the pharmacokinetics of codeine and its metabolites.

METHOD

A blood sample was collected from healthy Mongolian volunteers for CYP2D6 genotyping using a PCR-RFLP assay. A pharmacokinetic study was then carried out in three groups with CYP2D6*1/*1 (n=10), CYP2D6*1/*10 (n=10) and CYP2D6*10/*10 (n=9) genotypes by collecting serial blood samples for determination of plasma levels of codeine and its metabolites, morphine, morphine 3-glucuronide (M3G) and morphine 6-glucuronide (M6G) before and after a single 30-mg oral dose of codeine phosphate. Codeine and its metabolites were measured by LC-MS/MS.

RESULTS

No significant differences were observed in the pharmacokinetic parameters of codeine in the three genotype groups. However, the C( max) and AUC(0-∞) of morphine, M3G and M6G were significantly different between the study groups (P<0.05). Compared with the *1/*1 group, the AUC(0-∞) for morphine in the *1/*10 and *10/*10 groups decreased by ratios (95 % CI) of 0.93 (0.26-1.59) and 0.494 (0.135-0.853) respectively. Corresponding ratios for M3G were 0.791 (0.294-1.288) and 0.615 (0.412-0.818) and for M6G were 0.643 (0.39-0.957) and 0.423 (0.267-0.579).

CONCLUSION

This study demonstrates that the CYP2D6*10 allele plays an important role in the pharmacokinetics of the O-demethylated metabolites of codeine after oral administration.