Pharmacogenetics of chronic pain management

Genetic Testing for Opioid Pain Management: A Primer

Patients see their primary care physicians (PCPs) for a variety of medical conditions, chronic pain being one of the most common. An increased use of prescription medications (especially opioids) has led to an increase in adverse drug reactions and has heightened our awareness of the variability in response to medications. Opioids and other pain adjuvants are widely used, and drug-drug interactions involving these analgesics can be problematic and potentially lethal. Pharmacogenetics has improved our understanding of drug efficacy and response, opened doors to individual tailoring of medical management, and created a series of ethical and economic considerations. Since it is a relatively new field, genetic testing has not been fully integrated into the primary care setting. The purpose of this paper is to review the metabolism of commonly prescribed opioids, discuss the economic and ethical issues, and provide PCPs with an understanding of how to incorporate genetic testing into routine use to improve clinical practice and patient management.

Complications of Psychotropic and Pain Medications in an Ultrarapid Metabolizer Patient at the Upper 1% of Cytochrome P450 (CYP450) Function Quantified by Combinatorial CYP450 Genotyping

A 44-year-old Caucasian woman presented with a history of empirical treatment with 20 pain and psychotropic medications, as well as dual comorbidity of intractable pain and depression. A multiple gain-of-function profile in the CYP450 family of cytochrome P450 (CYP450) drug metabolism isoenzymes was discovered. The patient was a homozygote of suprafunctional alleles for both CYP2D6 (^*35/^*35) and CYP2C19 (^*17/^*17) genes and functional alleles for CYP2C9 (^*1/^*1), which account for aggregate drug metabolism function at the upper 1% of the population. The patient improved clinically with discontinuation of psychotropics and pain medications that were substrates of CYP2D6 and/or CYP2C19, suggesting that much of her symptomatology was drug induced. Combinatorial genotyping of CYP450 genes is diagnostically useful in individuals with histories of multiple side effects or drug resistance, which could be avoided by genetically informed therapeutics in behavioral health.

A Novel Sensitive Method to Measure Catechol-O-Methyltransferase Activity Unravels the Presence of This Activity in Extracellular Vesicles Released by Rat Hepatocytes

There is a clear need for drug treatments to be selected according to the characteristics of an individual patient, in order to improve efficacy and reduce the number and severity of adverse drug reactions. One of the main enzymes to take into account in pharmacogenomics is catechol O-methyltransferase (COMT), which catalyzes the transfer of a methyl group from S-adenosylmethionine to catechols and catecholamines, like the neurotransmitters dopamine, epinephrine, and norepinephrine. Although, most of this enzyme is associated to intracellular vesicles, recently it has also been detected in extracellular vesicles secreted by hepatocytes and in serum circulating vesicles. COMT has implications in many neurological and psychiatric disorders like Parkinson's disease, chronic fatigue, pain response, schizophrenia, and bipolar disorders. Remarkably, genetic variations of COMT affect its activity and are associated to various human disorders from psychiatric diseases to estrogen-induced cancers. Consequently, the establishment of new methods to evaluate COMT activity is an important aspect to investigate the biology of this drug-metabolizing enzyme. Herein, we have developed a sensitive and selective method to determine COMT activity. We first optimized the activity in rat liver incubated with two different substrates; norepinephrine and dopamine. The enzymatically formed products (normetanephrine and 3-methoxytyramine, respectively) were extracted by solid-phase extraction using weak cation exchange cartridges, chromatographically separated, and detected and quantified using a mass spectrometer. The range of quantitation for both products was from 0.005 to 25 μg/mL. This methodology offers acceptable recovery for both enzymatic products (≥75%) and good accuracy and precision (≤15%). The lower limit of quantifications were 0.01 and 0.005 μM for 3-methoxytyramine and normetanephrine, respectively. Importantly, this sensitive assay was able to detect the presence of COMT activity in extracellular vesicles secreted by hepatocytes supporting a potential role of these vesicles in catecholamines and catecholestrogens metabolisms. In addition, the presence of COMT activity in extracellular vesicles opens new possibilities to develop tools to evaluate personalized drug response in a low invasive manner.

‘Omics’: an emerging field in pain research and management

Precision medicine is an emerging approach for prevention and treatment of diseases considering individuals’ uniqueness. Omics provide one step forward toward advanced precision medicine and include technologies such as genomics, proteomics and metabolomics generating valuable data through characterization of entire biological systems. With the aid of omics, a major shift has been started to occur in understanding of diseases followed by potential fundamental changes in medical care strategies. This short review aims at providing some examples of current omics that are applied in the field of pain in terms of new biomarkers for diagnosis of different pain types, stratification of patients and new therapeutic targets. Implementation of omics would most likely offer breakthrough in the future of pain management.

Pharmacotherapies in Geriatric Chronic Pain Management

Pharmacologic management of chronic pain in older adults is one component of the multimodal, interdisciplinary management of this complex condition. In this article, we summarize several of the key barriers to effective pharmacologic management in older adults and review the existing (albeit limited) evidence for its effectiveness and safety, especially in a medically complex population with multimorbidity. This review covers topical formulations, acetaminophen, oral nonsteroidal antiinflammatory drugs, and adjuvant therapies. The article concludes with a suggested approach to managing chronic pain in the older patient, incorporating goals and expectations for treatment as well as careful monitoring of medication adjustments.

Perioperative management in children with chronic pain

Children with chronic pain often undergo surgery and effective perioperative management of their pain can be challenging. Identification of the pediatric chronic pain patient preoperatively and development of a perioperative pain plan may help ensure a safer and more comfortable perioperative course. Successful management usually requires multiple different classes of analgesics, regional anesthesia, and adjunctive nonpharmacological therapies. Neuropathic and oncological pain can be especially difficult to treat and usually requires an individualized approach.

Pharmacogenomics of multifactorial diseases: a focus on psoriatic arthritis

This review will outline the current pharmacogenomics knowledge about psoriatic arthritis with a special attention to the perspectives and the challenges for its implementation in the clinical practice. To date, different drugs have been developed to contrast the symptoms and the progression of psoriatic arthritis. However, patients have shown high variability of drug response in relation to their genetic makeup. In this context, the advances made in the knowledge and the potentialities of genome-drugs associations paved the path for the development of a precision medicine. In fact, these associations may be successfully combined with the environment information to provide new strategies able to prevent and improve the disease management as well as to enhance the patients quality of life.

The pharmacogenomics of pain management: prospects for personalized medicine

Pain is a common symptom that can be complex to treat. Analgesic medications are the mainstay treatment, but there is wide interindividual variability in analgesic response and adverse effects. Pharmacogenomics is the study of inherited genetic traits that result in these individual responses to drugs. This narrative review will attempt to cover the current understanding of the pharmacogenomics of pain, examining common genes affecting metabolism of analgesic medications, their distribution throughout the body, and end organ effects.

Exploring the Use of Chronic Opioid Therapy for Chronic Pain: When, How, and for Whom?

This article provides a broad overview regarding intent to initiate and consider ongoing chronic opioid therapy (COT) for treatment of chronic noncancer pain (CNCP). COT should be an individualized decision based on a comprehensive evaluation, assessment, and monitoring. It is imperative that providers discuss various risks and benefits of COT initially and at follow-up visits, and continue appropriate monitoring and follow-up at regular intervals. The decision to initiate or continue opioid therapy is based on clinical judgment; however, it is understood that opioid and other medication therapy represent one piece of the complete treatment plan for patients with CNCP.

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.

Apoyo social percibido y afrontamiento en personas con dolor crónico no maligno

Objetivo: determinar la asociación entre el apoyo social percibido y el afrontamiento de las personas con dolor crónico no maligno en la ciudad de Tunja (Colombia). Materiales y método: estudio descriptivo, de correlación, con abordaje cuantitativo, de corte transversal, en el que participaron 340 personas con dolor crónico no maligno. El análisis se realizó empleando estadística descriptiva y determinación de la correlación a través del coeficiente de correlación de Pearson. Resultados: las personas con dolor crónico no maligno participantes en el estudio fueron en su mayoría mujeres, con edades comprendidas entre los 36 a los 59 años, con niveles de escolaridad heterogéneos, estratos socioeconómicos bajos y ocupación hogar. La mayoría con patologías neurológicas o neuroquirúrgicas, seguidas por las de origen óseo o articular. La presencia de dolor supera los tres años y su intensidad severa. Se encontró alta percepción del apoyo social, así como alto uso de estrategias de afrontamiento, con predominio de la religión. Se identifica correlación débil estadísticamente significativa entre apoyo social percibido y afrontamiento en personas con dolor crónico, y entre apoyo social percibido y afrontamiento activo. Conclusiones: las intervenciones de apoyo social adaptadas a los contextos y ámbitos en los que se encuentran los usuarios, se deben considerar como iniciativas para fortalecer las estrategias de afrontamiento de personas con dolor crónico no maligno.

Non-opiate pharmacotherapy options for the management of pain in older adults

Pain is highly prevalent, costly, and disabling in later life, especially when undertreated. In this article, we aim to describe the risks and benefits of non-opioid medication options for the management of pain in adults aged 65 years and older in order to provide additional options in a practitioner's tool box when designing a pain management regimen for an older adult. Non-opiate pharmacologic therapies, such as acetaminophen, nonsteroidal anti-inflammatory drugs, topicals, and antidepressants have an important role in pain management of older adults. When designing a pain regimen, taking an individualized approach that considers the patient's functional status, comorbidities, and treatment goals will maximize pain management.

Pharmacogenetics and analgesic effects of antidepressants in chronic pain management

Antidepressants are widely administered to chronic pain patients, but there is large interindividual variability in their efficacy and adverse effect rates that may be attributed to genetic factors. Studies have attempted to determine the impact of genetic polymorphisms in enzymes and transporters that are involved in antidepressant pharmacokinetics, for example, cytochrome P450 and P-gp. The impacts of genetic polymorphisms in the targets of antidepressants, such as the serotonin receptor or transporter, the noradrenaline transporter and the COMT and monoamine oxydase enzymes, have also been described. This manuscript discusses the current knowledge of the influence of genetic factors on the plasma concentrations, efficacy and adverse effects of the major antidepressants used in pain management.

Management of the patient with chronic pain

Chronic pain is a significant complex problem in the perioperative environment. The management of patients with chronic pain has presented new challenges to anesthesia providers in the perioperative setting. The treatment of pain is often inadequate, and patients with preexisting chronic pain are not being managed properly. Although numerous techniques for intraoperative analgesia have been established, no official guidelines have been published for the growing population of patients with chronic pain. This article provides insight into and awareness of the various elements that should be addressed, along with interventions for the patient with chronic pain in the perioperative setting.

The use of opioids for treatment of cancer pain

INTRODUCTION

Pain is commonly experienced by patients with cancer, particularly those with advanced disease. Alleviating pain is an important goal of cancer treatment. Opioids are the cornerstone of the analgesic treatment.

AREAS COVERED

Pharmacology, characteristics, and use of opioids in clinical practice are presented.

EXPERT OPINION

Although the use of opioids is largely accepted as a fundamental step for controlling cancer pain, existing data supporting this statement are poor. All opioids provide analgesia and are effective in controlling cancer pain. New drugs have been developed and experience is accumulating among clinicians. Despite these drugs having different pharmacokinetic and chemical properties, there is no proof that one opioid is better than another one. Thus, the optimum benefit depends on the experience of the users. Clinicians should weight evidence, clinical experience, patient preferences, and treatment costs when choosing the optimal treatment for an individual patient with cancer pain. New opioids with specific receptor activities are under investigation.