Analgesic effect of clobazam in chronic low-back pain but not in experimentally induced pain

Predictors of success of pharmacological management in patients with chronic lower back pain: systematic review

BACKGROUND

Conservative management is recommended as the first therapeutic step in chronic low back pain (LBP), but there is no available evidence regarding the possible effect of patients' baseline characteristics on the therapeutic outcomes. A systematic review of the literature was performed to investigate this point.

METHODS

In February 2024, all the level I studies investigating the role of pharmacological management for chronic LBP were accessed. Data concerning the patient demographic at baseline were collected: number of patients and related mean BMI and age, duration of the symptoms, duration of the follow-up, percentage of females, Numeric Rating Scale (NRS), the Roland Morris Disability Questionnaire (RMQ), Oswestry Disability Index (ODI). The outcomes at the last follow-up were evaluated through NRS, RMQ, and ODI. A multiple linear model regression diagnostic through the Pearson Product-Moment Correlation Coefficient (r) was used.

RESULTS

Data from 47 articles (9007 patients) were obtained. The analysis yielded the following significant associations: age at baseline and NRS at follow-up (r = - 0.22; P = 0.04), NRS at baseline with NRS (r = 0.26; P = 0.03) and RMQ (r = - 0.58; P = 0.02) at follow-up, RMQ at baseline and the same at follow-up (r = 0.69; P = 0.0001).

CONCLUSION

Older age, higher BMI, presence of comorbidities, higher ODI and a long history of symptoms or surgical treatments do not reduce the efficacy of pharmacological management of chronic LBP. However, pharmacological therapy is not an effective option for patients with high baseline RMQ.

LEVEL OF EVIDENCE

I systematic review of RCTs.

Developing non-opioid therapeutics to alleviate pain among persons with opioid use disorder: a review of the human evidence

The opioid crisis remains a major public health concern, causing significant morbidity and mortality worldwide. Pain is frequently observed among individuals with opioid use disorder (OUD), and the current opioid agonist therapies (OAT) have limited efficacy in addressing the pain needs of this population. We reviewed the most promising non-opioid analgesic therapies for opioid-dependent individuals synthesising data from randomised controlled trials in the Medline database from December 2022 to March 2023. Ketamine, gabapentin, serotoninergic antidepressants, and GABAergic drugs were found to be the most extensively studied non-opioid analgesics with positive results. Additionally, we explored the potential of cannabinoids, glial activation inhibitors, psychedelics, cholecystokinin antagonists, alpha-2 adrenergic agonists, and cholinergic drugs. Methodological improvements are required to advance the development of novel analgesic strategies and establish their safety profile for opioid-dependent populations. We highlight the need for greater integration of experimental pain methods and abuse liability assessments, more granular assessments of prior opioid exposure, greater uniformity of pain types within study samples, and a particular focus on individuals with OUD receiving OAT. Finally, future research should investigate pharmacokinetic interactions between OAT and various non-opioid analgesics and perform reverse translation basic experiments, particularly with methadone and buprenorphine, which remain the standard OUD treatment.

Efficacy, acceptability, and safety of muscle relaxants for adults with non-specific low back pain: systematic review and meta-analysis

OBJECTIVE

To investigate the efficacy, acceptability, and safety of muscle relaxants for low back pain.

DESIGN

Systematic review and meta-analysis of randomised controlled trials.

DATA SOURCES

Medline, Embase, CINAHL, CENTRAL, ClinicalTrials.gov, clinicialtrialsregister.eu, and WHO ICTRP from inception to 23 February 2021.

ELIGIBILITY CRITERIA FOR STUDY SELECTION

Randomised controlled trials of muscle relaxants compared with placebo, usual care, waiting list, or no treatment in adults (≥18 years) reporting non-specific low back pain.

DATA EXTRACTION AND SYNTHESIS

Two reviewers independently identified studies, extracted data, and assessed the risk of bias and certainty of the evidence using the Cochrane risk-of-bias tool and Grading of Recommendations, Assessment, Development and Evaluations, respectively. Random effects meta-analytical models through restricted maximum likelihood estimation were used to estimate pooled effects and corresponding 95% confidence intervals. Outcomes included pain intensity (measured on a 0-100 point scale), disability (0-100 point scale), acceptability (discontinuation of the drug for any reason during treatment), and safety (adverse events, serious adverse events, and number of participants who withdrew from the trial because of an adverse event).

RESULTS

49 trials were included in the review, of which 31, sampling 6505 participants, were quantitatively analysed. For acute low back pain, very low certainty evidence showed that at two weeks or less non-benzodiazepine antispasmodics were associated with a reduction in pain intensity compared with control (mean difference -7.7, 95% confidence interval-12.1 to-3.3) but not a reduction in disability (-3.3, -7.3 to 0.7). Low and very low certainty evidence showed that non-benzodiazepine antispasmodics might increase the risk of an adverse event (relative risk 1.6, 1.2 to 2.0) and might have little to no effect on acceptability (0.8, 0.6 to 1.1) compared with control for acute low back pain, respectively. The number of trials investigating other muscle relaxants and different durations of low back pain were small and the certainty of evidence was reduced because most trials were at high risk of bias.

CONCLUSIONS

Considerable uncertainty exists about the clinical efficacy and safety of muscle relaxants. Very low and low certainty evidence shows that non-benzodiazepine antispasmodics might provide small but not clinically important reductions in pain intensity at or before two weeks and might increase the risk of an adverse event in acute low back pain, respectively. Large, high quality, placebo controlled trials are urgently needed to resolve uncertainty.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42019126820 and Open Science Framework https://osf.io/mu2f5/.

Comparative safety review of current treatment options for chronic low back pain and unmet needs: a narrative review

Introduction: The healthcare expenditures in the United States are substantial for the management of refractory, chronic low back pain (CLBP). The objective of this review is to summarize and evaluate the safety profiles of different pharmacological treatment options used in the management of CLBP.Areas covered: The authors conducted a search of randomized controlled trials (RCTs) assessing the safety profiles of different pharmacological agents used in the management of CLBP. This narrative review covered corticosteroids, opioids, antidepressants, gabapentinoids, nonsteroidal anti-inflammatory drugs, muscle relaxants, anti-nerve growth factor antibodies and topical agents, as monotherapy or in combination.Expert opinion: The risk-benefit ratio of a particular treatment is a subject driving the ongoing development of pharmaceuticals. The most commonly reported AEs across all drug classes are of gastrointestinal nature, followed by neurological and skin-related. These AEs include nausea, dizziness, constipation, arthralgia, headache, dry mouth, pruritus, etc. The majority of the AEs reported are not life-threatening, although they may lower patients' quality of life, thus, affecting their compliance. One of the biggest limitations of our review stems from the paucity of safety assessments in published RCTs. Advances in our understanding of the neurobiology of pain will promote development of new therapeutic strategies.

The pharmacological management of chronic lower back pain

INTRODUCTION

Treating chronic low back pain (LBP) can be challenging, and the most effective pharmacological therapy is controversial. The present systematic review investigated the efficacy of various pharmacological compounds to achieve pain relief and improve disability in chronic LBP patients. The present study focused on acetaminophen, amoxicillin, flupirtine, baclofen, tryciclic antidepressants (TCAs), duloxetine, topiramate, gabapentinoids, non-steroid anti-inflammatory drugs (NSAIDs) and opioids.

AREAS COVERED

All randomized clinical trials comparing two or more drug treatments for chronic low back pain were accessed. Studies reporting outcomes concerning patients with neurologic or mechanic, specific or aspecific low back pain with or without radiculopathy were included. LBP was considered chronic if pain had lasted more than 6 weeks. Data from 47 articles (9007 patients: mean age: 52.62 ± 7.0 years; mean BMI: 28.26 ± 2.8; mean follow-up: 3.23 ± 3.2 months) were obtained.

EXPERT OPINION

According to published level I evidence, only baclofen, duloxetine, NSAIDs, and opiates showed to improve pain and disability levels in patients with LBP. However, the patients' demographics are heterogeneous, and the results must be interpreted with caution and in the light of possible adverse events connected to the use of these drugs.

Pentameric Ligand-Gated Ion Channels as Pharmacological Targets Against Chronic Pain

Chronic pain is a common detrimental condition that affects around 20% of the world population. The current drugs to treat chronic pain states, especially neuropathic pain, have a limited clinical efficiency and present significant adverse effects that complicates their regular use. Recent studies have proposed new therapeutic strategies focused on the pharmacological modulation of G-protein-coupled receptors, transporters, enzymes, and ion channels expressed on the nociceptive pathways. The present work intends to summarize recent advances on the pharmacological modulation of pentameric ligand-gated ion channels, which plays a key role in pain processing. Experimental data have shown that novel allosteric modulators targeting the excitatory nicotinic acetylcholine receptor, as well as the inhibitory GABA_A and glycine receptors, reverse chronic pain-related behaviors in preclinical assays. Collectively, these evidences strongly suggest the pharmacological modulation of pentameric ligand-gated ion channels is a promising strategy towards the development of novel therapeutics to treat chronic pain states in humans.

A randomised, placebo-controlled clinical trial with the α2/3/5 subunit selective GABAA positive allosteric modulator PF-06372865 in patients with chronic low back pain

The effect of PF-06372865, a subtype-selective positive allosteric modulator of the γ-aminobutyric acid type A (GABAA) receptor, on chronic low back pain was investigated in a randomised, placebo- and active-controlled phase 2 clinical trial. The parallel treatment group trial consisted of a 1-week single-blind placebo run in the phase, followed by 4-week double-blind treatment. Patients were randomised to receive either PF-06372865, naproxen, or placebo twice a day for 4 weeks. The primary end point was the numerical rating score of low back pain intensity after 4 weeks of active treatment. Secondary end points included the Roland Morris Disability Questionnaire and the Hopkins Verbal Learning Test-Revised. The trial had predefined decision rules based on the probability that PF-06372865 was better than placebo. The study was stopped at the interim analysis for futility. At this time, a total of 222 patients were randomised and the mean PF-06372865 4-week response on the low back pain intensity was 0.16 units higher (worse) than placebo (90% confidence interval -0.28 to 0.60). There were small, statistically significant reductions in the delayed recall test score with PF-06372865, as measured by Hopkins Verbal Learning Test-Revised. The effects of naproxen were in line with expectations. PF-06372865 was well tolerated. The most common treatment-related adverse events in the PF-06372865 arm were somnolence (5 mild and 4 moderate), dizziness (2 mild and 3 moderate), and nausea (2 mild). Although the reason for the lack of analgesic effect is not completely clear, it may be a result of not achieving sufficient receptor occupancy to drive efficacy.

Disruption of cortical synaptic homeostasis in individuals with chronic low back pain

OBJECTIVE

Homeostatic plasticity mechanisms regulate synaptic plasticity in the human brain. Impaired homeostatic plasticity may contribute to maladaptive synaptic plasticity and symptom persistence in chronic musculoskeletal pain.

METHODS

We examined homeostatic plasticity in fifty individuals with chronic low back pain (cLBP) and twenty-five pain-free controls. A single block (7-min) of anodal transcranial direct current stimulation ('single tDCS'), or two subsequent blocks (7-min and 5-min separated by 3-min rest; 'double tDCS'), were randomised across two experimental sessions to confirm an excitatory response to tDCS applied alone, and evaluate homeostatic plasticity, respectively. Corticomotor excitability was assessed in the corticomotor representation of the first dorsal interosseous muscle by transcranial magnetic stimulation-induced motor evoked potentials (MEPs) recorded before and 0, 10, 20, and 30-min following each tDCS protocol.

RESULTS

Compared with baseline, MEP amplitudes increased at all time points in both groups following the single tDCS protocol (P < 0.003). Following the double tDCS protocol, MEP amplitudes decreased in pain-free controls at all time points compared with baseline (P < 0.01), and were unchanged in the cLBP group.

CONCLUSION

These data indicate impaired homeostatic plasticity in the primary motor cortex of individuals with cLBP.

SIGNIFICANCE

Impaired homeostatic plasticity could explain maladaptive synaptic plasticity and symptom persistence in cLBP.

Quantitative sensory tests fairly reflect immediate effects of oxycodone in chronic low-back pain

INTRODUCTION

Quantitative sensory tests (QST) can be used for profiling anti-nociceptive effects of analgesics. However, anti-nociceptive effects detected by QST are not necessarily associated with analgesic effects in pain patients. As part of a large investigation on low back pain, this paper describes the immediate analgesic and anti-nociceptive effects of oxycodone in chronic low-back pain and ranks different QST according to their ability to reflect this effect. The results are expected to support the selection of QST for future studies on potential novel opioid agonists in human pain.

METHODS

In this randomized, placebo-controlled and double-blinded cross-over study, 50 patients with chronic low-back pain received a single oral dose of oxycodone 15mg or active placebo, and underwent multiple QST testing. The intensity of low-back pain was recorded during 2h. The areas under the ROC curves and 95% confidence intervals were determined, whereby responder status (≥30% pain reduction) was set as reference variable and changes in QST from baseline were set as classifiers.

RESULTS

Significant analgesic effect on low-back pain as well as anti-nociceptive effects for almost all QST parameters were observed. The QST with the highest area under the curve were heat pain detection threshold (0.65, 95%-CI 0.46 to 0.83), single-stimulus electrical pain threshold (0.64, 95%-CI 0.47 to 0.80) and pressure pain detection threshold (0.63, 95%-CI 0.48 to 0.79).

CONCLUSIONS

The results suggest that anti-nociceptive effects assessed by QST fairly reflect clinical efficacy of oxycodone on low-back pain. Pressure pain detection threshold, heat pain detection threshold and single-stimulus electrical pain threshold may be more suitable to sort out potential non-responders rather than identifying potential responders to opioid medication. Future pre-clinical human research may consider these results when investigating the analgesic effect of opioid agonists by means of QST.