Coanalgesics for Chronic Pain Therapy: A Narrative Review

Adjuvant Analgesics in Acute Pain - Evaluation of Efficacy

PURPOSE OF THE REVIEW

Acute postoperative pain impacts a significant number of patients and is associated with various complications, such as a higher occurrence of chronic postsurgical pain as well as increased morbidity and mortality.

RECENT FINDINGS

Opioids are often used to manage severe pain, but they come with serious adverse effects, such as sedation, respiratory depression, postoperative nausea and vomiting, and impaired bowel function. Therefore, most enhanced recovery after surgery protocols promote multimodal analgesia, which includes adjuvant analgesics, to provide optimal pain control. In this article, we aim to offer a comprehensive review of the contemporary literature on adjuvant analgesics in the management of acute pain, especially in the perioperative setting. Adjuvant analgesics have proven efficacy in treating postoperative pain and reducing need for opioids. While ketamine is an established option for opioid-dependent patients, magnesium and α2-agonists have, in addition to their analgetic effect, the potential to attenuate hemodynamic responses, which make them especially useful in painful laparoscopic procedures. Furthermore, α2-agonists and dexamethasone can extend the analgesic effect of regional anesthesia techniques. However, findings for lidocaine remain inconclusive.

Autophagy: An Emerging Target for Developing Effective Analgesics

Inadequate treatment of acute and chronic pain causes depression, anxiety, sleep disturbances, and increased mortality. Abuse and overdose of opioids and the side effects associated with chronic use of NSAID illustrate the need for development of safer and effective pain medication. Working toward this end, an in silico tool based on an emergent intelligence analytical platform that examines interactions between protein networks was used to identify molecular mechanisms involved in regulating the body's response to painful stimuli and drug treatments. Examining interactions between protein networks associated with the expression of over 20 different pain types suggests that the regulation of autophagy plays a central role in modulation of pain symptoms (see Materials and Methods). Using the topology of this regulatory scheme as an in silico screening tool, we identified that combinations of functions targeted by cannabidiol, myo-inositol, and fish oils with varying ratios of eicosapentaenoic and docosahexaenoic acids are projected to produce superior analgesia. For validating this prediction, we administered combinations of cannabidiol, myo-inositol, and fish oils to rats that received formalin injections in hind paws, prior to substance administration, and showed that analgesic effects produced by these combinations were comparable or superior to known NSAID analgesics, which suggests that these combinations have potential in treatment of pain.

Cannabinoids and Pain: New Insights From Old Molecules

Cannabis has been used for medicinal purposes for thousands of years. The prohibition of cannabis in the middle of the 20th century has arrested cannabis research. In recent years there is a growing debate about the use of cannabis for medical purposes. The term ‘medical cannabis’ refers to physician-recommended use of the cannabis plant and its components, called cannabinoids, to treat disease or improve symptoms. Chronic pain is the most commonly cited reason for using medical cannabis. Cannabinoids act via cannabinoid receptors, but they also affect the activities of many other receptors, ion channels and enzymes. Preclinical studies in animals using both pharmacological and genetic approaches have increased our understanding of the mechanisms of cannabinoid-induced analgesia and provided therapeutical strategies for treating pain in humans. The mechanisms of the analgesic effect of cannabinoids include inhibition of the release of neurotransmitters and neuropeptides from presynaptic nerve endings, modulation of postsynaptic neuron excitability, activation of descending inhibitory pain pathways, and reduction of neural inflammation. Recent meta-analyses of clinical trials that have examined the use of medical cannabis in chronic pain present a moderate amount of evidence that cannabis/cannabinoids exhibit analgesic activity, especially in neuropathic pain. The main limitations of these studies are short treatment duration, small numbers of patients, heterogeneous patient populations, examination of different cannabinoids, different doses, the use of different efficacy endpoints, as well as modest observable effects. Adverse effects in the short-term medical use of cannabis are generally mild to moderate, well tolerated and transient. However, there are scant data regarding the long-term safety of medical cannabis use. Larger well-designed studies of longer duration are mandatory to determine the long-term efficacy and long-term safety of cannabis/cannabinoids and to provide definitive answers to physicians and patients regarding the risk and benefits of its use in the treatment of pain. In conclusion, the evidence from current research supports the use of medical cannabis in the treatment of chronic pain in adults. Careful follow-up and monitoring of patients using cannabis/cannabinoids are mandatory.

Chronic Pain: How Challenging Are DDIs in the Analgesic Treatment of Inpatients with Multiple Chronic Conditions?

Background

Chronic pain is common in multimorbid patients. However, little is known about the implications of chronic pain and analgesic treatment on multimorbid patients. This study aimed to assess chronic pain therapy with regard to the interaction potential in a sample of inpatients with multiple chronic conditions.

Methods and Findings

We conducted a retrospective study with all multimorbid inpatients aged ≥18 years admitted to the Department of Internal Medicine of University Hospital Zurich in 2011 (n = 1,039 patients). Data were extracted from the electronic health records and reviewed. We identified 433 hospitalizations of patients with chronic pain and analyzed their combinations of chronic conditions (multimorbidity). We then classified all analgesic prescriptions according to the World Health Organization (WHO) analgesic ladder. Furthermore, we used a Swiss drug-drug interactions knowledge base to identify potential interactions between opioids and other drug classes, in particular coanalgesics and other concomitant drugs. Chronic pain was present in 38% of patients with multimorbidity. On average, patients with chronic pain were aged 65.7 years and had a mean number of 6.6 diagnoses. Hypertension was the most common chronic condition. Chronic back pain was the most common painful condition. Almost 90% of patients were exposed to polypharmacotherapy. Of the chronic pain patients, 71.1% received opioids for moderate to severe pain, 43.4% received coanalgesics. We identified 3,186 potential drug-drug interactions, with 17% classified between analgesics (without coanalgesics).

Conclusions

Analgesic drugs-related DDIs, in particular opioids, in multimorbid patients are often complex and difficult to assess by using DDI knowledge bases alone. Drug-multimorbidity interactions are not sufficiently investigated and understood. Today, the scientific literature is scarce for chronic pain in combination with multiple coexisting medical conditions and medication regimens. Our work may provide useful information to enable further investigations in multimorbidity research within the scope of potential interactions and chronic pain.

Providing Care for Patients with Chronic Migraine: Diagnosis, Treatment, and Management

Chronic migraine, a subtype of migraine defined as ≥ 15 headache days per month for ≥ 3 months, in which ≥ 8 days per month meet criteria for migraine with or without aura or respond to migraine-specific treatment, is a disabling, underdiagnosed, and undertreated disorder associated with significant disability, poor health-related quality of life, and high economic burden. The keys to caring for chronic migraine patients include: (1) making a proper diagnosis; (2) identifying and eliminating exacerbating factors; (3) assessing for medication overuse (patients with chronic headache often overuse acute medications); and (4) continued management. Communication between patient and physician about treatment goals is important. The patient management guidelines presented in this article should help physicians improve treatment success and proactively address common comorbidities among their patients with chronic migraine.

Managing co-occurring substance use and pain disorders

The safest pain treatment strategy for an individual at risk or recovering from addiction is a nonopioid and benzodiazepine-free approach. If an opioid treatment is necessary, the extent of the risk can be stratified by the use of a biopsychosocial assessment and opioid screening tools. Individuals at high risk should have the greatest amount of structure and monitoring. A written informed consent and treatment agreement can provide a framework for the patient and the patient’s family, as well as the clinician. The structure of treatment should specify only that one prescribing physician will write a limited supply of opioids, without refills, until the analgesic efficacy, adverse events, and goals for functional restoration can be assessed. An additional recommendation is that prescriptions should be filled at the same pharmacy with no refill by phone or opportunity for replacement because of loss, damage, or stolen medications. Additionally, random urine drug screens and PDMP reports obtained will help determine if the patient is taking other substances, as well as monitor the patient’s medication use patterns. It is important to assess for risk factors in treating chronic pain with opioids; clinicians need to have a realistic appreciation of the resources available to them and the types of patients that can be managed in their practice. Chronic pain treatment with opioids should not be undertaken in patients who are currently addicted to illicit substances or alcohol. With the support of family and friends, ideally the patient can be motivated to participate in an intensive substance abuse treatment. In patients without an immediate risk, precautionary steps should be taken when prescribing opioids. Clinicians and patients need to review the risk factors for opioid-related problems including younger age, benzodiazepine use, and comorbid conditions such as depression, anxiety, and heavy smoking. Both the provider and the patient need a personal investment in the treatment plan and protocol to increase the safety of opioid treatment. New medications and treatment monitoring are being developed to provide maximal relief for the patient while protecting the public health. The optimal ingredients for safe opioid treatment include a strong provider-patient relationship and clinician training in the assessment and treatment of addiction and pain.