Opioid switching and variability in response in pain cancer patients

Implementing physics-based digital patient twins to tailor the switch of oral morphine to transdermal fentanyl patches based on patient physiology

Fentanyl transdermal patches are widely implemented for cancer-induced pain treatment due to the high potency of fentanyl and gradual drug release. However, transdermal fentanyl up-titration for opioid-naïve patients is difficult, which is why opioid treatment is often started with oral/iv morphine. Based on the daily dose of morphine, the initial dose of the fentanyl patch is decided upon. After reaching a stable level of pain, the switch is made from oral/iv morphine to transdermal fentanyl. There are standard calculation tools for transferring from oral/iv morphine to transdermal fentanyl, which is the same for all patients. By considering the variations in the physiology of the patients, a unique switching strategy cannot meet the needs of different patients. This study explores the outcome in terms of pain relief and minute ventilation during opioid therapy. For this, we used physics-based simulations on a virtually-generated population of patients, and we applied the same therapy to all patients. We could show that patients' physiology, such as gender, age, and weight, greatly impact the outcome of the therapy; as such, the correlation coefficient between pain intensity and age is 0.89, and the correlation coefficient between patient's weight and maximum plasma concentration of morphine and fentanyl is -0.98 and -0.97. Additionally, a different combination of the duration of overlap between morphine and fentanyl therapy with different doses of fentanyl was considered for the virtual patients to find the best opioid-switching strategy for each patient. We explored the impact of combining physiological features to determine the best-suited strategy for virtual patients. Our findings suggest that tailoring morphine and fentanyl therapy only based on a limited number of features is insufficient, and increasing the number of impactful physiological features positively influences the outcome of the therapy.

Conversion ratios: Why is it so challenging to construct opioid conversion tables?

Standardizing opioid management is challenging due to the absence of a ceiling dose, the unknown ideal therapeutic plasma level, and the lack of an clear relationship between dose and therapeutic response. Opioid rotation or conversion, which is switching from one opioid, route of administration, or both, to another, to improve therapeutic response and reduce toxicities, occurs in 20-40 percent of patients treated with opioids. Opioid conversion is often needed when there are adverse effects, toxicities, or inability to tolerate a certain opioid formulation. A majority of patients benefit from opioid conversion, leading to improved analgesia and less adverse effects. There are different published ways of converting opioids in the literature. This review of 20 years of literature is centered on opioid conversions and aims to discuss the complexity of converting opioids. We discuss study designs, outcomes and measures, pain phenotypes, patient characteristics, comparisons of equivalent doses between opioids, reconciling conversion ratios between opioids, routes, directional differences, half-lives and metabolites, interindividual variability, and comparison to package insert information. Palliative care specialists have not yet come to a consensus on the ideal opioid equianalgesic table; however, we discuss a recently updated table, based on retrospective evidence, that may serve as a gold standard for practical use in the palliative care population. More robust, well-designed studies are needed to validate and guide future opioid conversion data.

Opioid Switch Dosing in Chronic Cancer Pain: A Prospective Longitudinal Study

Background: Opioid switching is common, however, conversion tables have limitations. Guidelines suggest postswitch dose reduction, yet, observations show opioid doses may increase postswitch. Objectives: To document the opioid conversion factor postswitch in cancer, and whether pain and adverse effect outcomes differ between switched opioid groups. Design/Setting: This multicenter prospective longitudinal study included people with advanced cancer in Australia. Clinical data (demographics, opioids) and validated instruments (pain, adverse effects) were collected twice, seven days apart. Results: Opioid switch resulted in dose increase (median oral morphine equivalent daily dose 90 mg [interquartile range {IQR} 45-184] to 150 mg [IQR 79-270]), reduced average pain (5.1 [standard deviation {SD} 1.7] to 3.8 [SD 1.6]), and reduced adverse effects. Hydromorphone dose increased 2.5 times (IQR 1.0-3.6) above the original conversion factor used. Conclusions: Opioid switching resulted in overall dose increase, particularly when switching to hydromorphone. Higher preswitch dosing may require higher dose conversion ratios. Dose reduction postswitch risks undertreatment and may not be always appropriate.

NLR family pyrin domain containing 3 (NLRP3) inflammasomes and peripheral neuropathic pain - Emphasis on microRNAs (miRNAs) as important regulators

Neuropathic pain is caused by the lesion or disease of the somatosensory system and can be initiated and/or maintained by both central and peripheral mechanisms. Nerve injury leads to neuronal damage and apoptosis associated with the release of an array of pathogen- or damage-associated molecular patterns to activate inflammasomes. The activation of the NLR family pyrin domain containing 3 (NLRP3) inflammasome contributes to neuropathic pain and may represent a novel target for pain therapeutic development. In the current review, we provide an up-to-date summary of the recent findings on the involvement of NLRP3 inflammasome in modulating neuropathic pain development and maintenance, focusing on peripheral neuropathic conditions. Here we provide a detailed review of the mechanisms whereby NLRP3 inflammasomes contribute to neuropathic pain via (1) neuroinflammation, (2) apoptosis, (3) pyroptosis, (4) proinflammatory cytokine release, (5) mitochondrial dysfunction, and (6) oxidative stress. We then present the current research literature reporting on the antinociceptive effects of several natural products and pharmacological interventions that target activation, expression, and/or regulation of NLRP3 inflammasome. Furthermore, we emphasize the effects of microRNAs as another regulator of NLRP3 inflammasome. In conclusion, we summarize the possible caveats and future perspectives that might provide successful therapeutic approaches against NLRP3 inflammasome for treating or preventing neuropathic pain conditions.

Effectiveness of Opioid Switching in Advanced Cancer Pain: A Prospective Observational Cohort Study

Opioid switching is a common practice of substituting one opioid for another to improve analgesia or adverse effects; however, it has limited evidence. This study aimed to examine the effectiveness of opioid switching in advanced cancer. This multi-center prospective cohort study recruited patients assessed to switch opioids (opioid switch group) or to continue ongoing opioid treatment (control group). Clinical data (demographics, opioids) and validated instruments (pain and adverse effects) were collected over two timepoints seven days apart. Descriptive analyses were utilized. Non-parametric tests were used to determine differences. Fifty-four participants were recruited (23 control group, 31 switch group). At the follow-up, opioid switching reduced pain (worst, average, and now) (p < 0.05), uncontrolled breakthrough pain (3-fold reduction, p = 0.008), and psychological distress (48% to 16%, p < 0.005). The switch group had a ≥25% reduction in the reported frequency of seven moderate-to-severe adverse effects (score ≥ 4), compared to a reduction in only one adverse effect in the control group. The control group experienced no significant pain differences at the follow-up. Opioid switching is effective at reducing pain, adverse effects, and psychological distress in a population with advanced cancer pain, to levels of satisfactory symptom control in most patients within 1 week.

Role of Cannabidiol for Improvement of the Quality of Life in Cancer Patients: Potential and Challenges

There is currently a growing interest in the use of cannabidiol (CBD) to alleviate the symptoms caused by cancer, including pain, sleep disruption, and anxiety. CBD is often self-administered as an over-the-counter supplement, and patients have reported benefits from its use. However, despite the progress made, the mechanisms underlying CBD’s anti-cancer activity remain divergent and unclear. Herein, we provide a comprehensive review of molecular mechanisms to determine convergent anti-cancer actions of CBD from pre-clinical and clinical studies. In vitro studies have begun to elucidate the molecular targets of CBD and provide evidence of CBD’s anti-tumor properties in cell and mouse models of cancer. Furthermore, several clinical trials have been completed testing CBD’s efficacy in treating cancer-related pain. However, most use a mixture of CBD and the psychoactive, tetrahydrocannabinol (THC), and/or use variable dosing that is not consistent between individual patients. Despite these limitations, significant reductions in pain and opioid use have been reported in cancer patients using CBD or CBD+THC. Additionally, significant improvements in quality-of-life measures and patients’ overall satisfaction with their treatment have been reported. Thus, there is growing evidence suggesting that CBD might be useful to improve the overall quality of life of cancer patients by both alleviating cancer symptoms and by synergizing with cancer therapies to improve their efficacy. However, many questions remain unanswered regarding the use of CBD in cancer treatment, including the optimal dose, effective combinations with other drugs, and which biomarkers/clinical presentation of symptoms may guide its use.

Integrating pharmacogenomics into precision pain management

Studies suggest wide heterogeneity in pain management response. Improved methods of pain pharmacotherapy are urgently needed to improve clinical response and safety profile of analgesics. The study or application of how genetics influence response to medications is called pharmacogenomics (PGx). PGx testing is a tool that may support more precise selection and dosing of pain medicines. PGx guidelines exist for drug-gene interactions with high levels of evidence and can be applied in clinical practice for more precise care in patients with cancer. The Clinical Pharmacogenetics Implementation Consortium (CPIC) is a publicly funded international consortium of experts who curate published PGx data and create peer-reviewed guidelines on how to translate PGx results into actionable prescribing decisions. Given the immense need to improve pain management, it is important to increase awareness and consider application of CPIC guidelines to pain management strategies. This commentary concisely describes how PGx can be used to aid in more precise applications of pain pharmacotherapy based on the CPIC guidelines.

Practice review: Evidence-based and effective management of pain in patients with advanced cancer

BACKGROUND

Pain of a moderate or severe intensity affects over half of patients with advanced cancer and remains undertreated in at least one-third of these patients.

AIM

The aim of this study was to provide a pragmatic overview of the evidence supporting the use of interventions in pain management in advanced cancer and to identify where encouraging preliminary results are demonstrated but further research is required.

DESIGN

A scoping review approach was used to examine the evidence supporting the use of guideline-recommended interventions in pain management practice.

DATA SOURCES

National or international guidelines were selected if they described pain management in adult cancer patients and were written within the last 5 years in English. The Cochrane Database of Systematic Reviews (January 2014 to January 2019) was searched for 'cancer' AND 'pain' in the title, abstract or keywords. A MEDLINE search was also made.

RESULTS

A strong opioid remains the drug of choice for treating moderate or severe pain. Bisphosphonates and radiotherapy are also effective for cancer-related bone pain. Optimal management requires a tailored approach, support for self-management and review of treatment outcomes. There is likely a role for non-pharmacological approaches. Paracetamol should not be used in patients taking a strong opioid to treat pain. Cannabis-based medicines are not recommended. Weak opioids, ketamine and lidocaine are indicated in specific situations only.

CONCLUSION

Interventions commonly recommended by guidelines are not always supported by a robust evidence base. Research is required to evaluate the efficacy of non-steroidal anti-inflammatory drugs, anti-convulsants, anti-depressants, corticosteroids, some invasive anaesthetic techniques, complementary therapies and transcutaneous electrical nerve stimulation.

The Efficacy of Medical Marijuana in the Treatment of Cancer-Related Pain

Background: The opioid epidemic has spurred investigations for nonopioid options, yet limited research persists on medical marijuana's (MMJ) efficacy in managing cancer-related symptoms. Objective: We sought to characterize MMJ's role on symptomatic relief and opioid consumption in the oncologic population. Design: Retrospective chart review of MMJ-certified oncology patients was performed. Divided patients into MMJ use [MMJ(+)] versus no use [MMJ(-)], and Edmonton Symptom Assessment System (ESAS)-reported pain cohorts: "mild-moderate" versus "severe." Measurements: Medical records were reviewed for ESAS, to measure physical and emotional symptoms, and opiate consumption, converted into morphine milligram equivalents (MME). Minimal clinically important differences were determined. Wilcoxon signed-rank tests determined statistical significance between MMJ-certification and most recent palliative care visit. Results: Identified 232 patients [95/232 MMJ(-); 137/232 MMJ(+)]. Pain, physical and total ESAS significantly improved for total MMJ(-) and MMJ(+); however, only MMJ(+) significantly improved emotional ESAS. MMJ(-) opioid consumption increased by 23% (97.5-120 mg/day MME, p = 0.004), while it remained constant (45-45 mg/day MME, p = 0.522) in MMJ(+). Physical and total ESAS improved in mild-moderate-MMJ(-) and MMJ(+). Pain and emotional symptoms worsened in MMJ(-); while MMJ(+)'s pain remained unchanged and emotional symptoms improved. MMJ(-) opioid consumption increased by 29% (90-126 mg/day MME, p = 0.012); while MMJ(+)'s decreased by 33% (45-30 mg/day MME, p = 0.935). Pain, physical, emotional, and total ESAS scores improved in severe-MMJ(-) and MMJ(+); opioid consumption reduced by 22% in MMJ(-) (135-106 mg/day MME, p = 0.124) and 33% in MMJ(+) (90-60 mg/day MME, p = 0.421). Conclusions: MMJ(+) improved oncology patients' ESAS scores despite opioid dose reductions and should be considered a viable adjuvant therapy for palliative management.

The Burden of Opioid Adverse Events and the Influence on Cancer Patients' Symptomatology

CONTEXT

Opioids are frequently used for the treatment of moderate-to-severe pain and their use may produce a number of unwanted adverse events (AEs).

OBJECTIVES

The objective of this study was to understand the burden of opioid-induced AEs in cancer patients with pain after the introduction of strong opioids (WHO Step III).

METHODS

This is a cohort study derived from a randomized controlled trial involving 498 cancer patients with pain who received strong opioids. During 28-day follow-up, we analyzed frequency, intensity, and changes over time of the main opioid-induced AEs; the influence of previous pain therapy on AEs; and the relationships between the presence of AEs and analgesic response.

RESULTS

After starting strong opioids, dry mouth, nausea, and vomiting immediately increased and persisted over time, constipation continued to increase, while drowsiness and confusion tended to decrease. Patients previously treated with weak opioids had more frequent and severe AEs. While at all observation points the percentage of patients without AEs was 37%-39%, considering all the five scheduled visits, from Day 3 to Day 28, 17% of patients never experienced any AEs, while 48% of patients had four or more concomitant AEs. Patients with no AEs experienced significantly lower pain intensity.

CONCLUSION

Opioid introduction induces various AEs that persist over time and worse patients' symptomatology. Moreover, there seems to be a different expression of the opioid toxicity among patients, and a possible interaction between AEs and the analgesic response. The balance between the opioids analgesic effect and induced toxicity is fundamental in deciding the best management for pain in cancer patients.