New developments in the use of tricyclic antidepressants for the management of pain

Pharmacological treatments for low back pain in adults: an overview of Cochrane Reviews

BACKGROUND

Pharmacological interventions are the most used treatment for low back pain (LBP). Use of evidence from systematic reviews of the effects of pharmacological interventions for LBP published in the Cochrane Library, is limited by lack of a comprehensive overview.

OBJECTIVES

To summarise the evidence from Cochrane Reviews of the efficacy, effectiveness, and safety of systemic pharmacological interventions for adults with non-specific LBP.

METHODS

The Cochrane Database of Systematic Reviews was searched from inception to 3 June 2021, to identify reviews of randomised controlled trials (RCTs) that investigated systemic pharmacological interventions for adults with non-specific LBP. Two authors independently assessed eligibility, extracted data, and assessed the quality of the reviews and certainty of the evidence using the AMSTAR 2 and GRADE tools. The review focused on placebo comparisons and the main outcomes were pain intensity, function, and safety.

MAIN RESULTS

Seven Cochrane Reviews that included 103 studies (22,238 participants) were included. There is high confidence in the findings of five reviews, moderate confidence in one, and low confidence in the findings of another. The reviews reported data on six medicines or medicine classes: paracetamol, non-steroidal anti-inflammatory drugs (NSAIDs), muscle relaxants, benzodiazepines, opioids, and antidepressants. Three reviews included participants with acute or sub-acute LBP and five reviews included participants with chronic LBP. Acute LBP Paracetamol There was high-certainty evidence for no evidence of difference between paracetamol and placebo for reducing pain intensity (MD 0.49 on a 0 to 100 scale (higher scores indicate worse pain), 95% CI -1.99 to 2.97), reducing disability (MD 0.05 on a 0 to 24 scale (higher scores indicate worse disability), 95% CI -0.50 to 0.60), and increasing the risk of adverse events (RR 1.07, 95% CI 0.86 to 1.33). NSAIDs There was moderate-certainty evidence for a small between-group difference favouring NSAIDs compared to placebo at reducing pain intensity (MD -7.29 on a 0 to 100 scale (higher scores indicate worse pain), 95% CI -10.98 to -3.61), high-certainty evidence for a small between-group difference for reducing disability (MD -2.02 on a 0-24 scale (higher scores indicate worse disability), 95% CI -2.89 to -1.15), and very low-certainty evidence for no evidence of an increased risk of adverse events (RR 0.86, 95% CI 0. 63 to 1.18). Muscle relaxants and benzodiazepines There was moderate-certainty evidence for a small between-group difference favouring muscle relaxants compared to placebo for a higher chance of pain relief (RR 0.58, 95% CI 0.45 to 0.76), and higher chance of improving physical function (RR 0.55, 95% CI 0.40 to 0.77), and increased risk of adverse events (RR 1.50, 95% CI 1. 14 to 1.98). Opioids None of the included Cochrane Reviews aimed to identify evidence for acute LBP. Antidepressants No evidence was identified by the included reviews for acute LBP. Chronic LBP Paracetamol No evidence was identified by the included reviews for chronic LBP. NSAIDs There was low-certainty evidence for a small between-group difference favouring NSAIDs compared to placebo for reducing pain intensity (MD -6.97 on a 0 to 100 scale (higher scores indicate worse pain), 95% CI -10.74 to -3.19), reducing disability (MD -0.85 on a 0-24 scale (higher scores indicate worse disability), 95% CI -1.30 to -0.40), and no evidence of an increased risk of adverse events (RR 1.04, 95% CI -0.92 to 1.17), all at intermediate-term follow-up (> 3 months and ≤ 12 months postintervention). Muscle relaxants and benzodiazepines There was low-certainty evidence for a small between-group difference favouring benzodiazepines compared to placebo for a higher chance of pain relief (RR 0.71, 95% CI 0.54 to 0.93), and low-certainty evidence for no evidence of difference between muscle relaxants and placebo in the risk of adverse events (RR 1.02, 95% CI 0.67 to 1.57). Opioids There was high-certainty evidence for a small between-group difference favouring tapentadol compared to placebo at reducing pain intensity (MD -8.00 on a 0 to 100 scale (higher scores indicate worse pain), 95% CI -1.22 to -0.38), moderate-certainty evidence for a small between-group difference favouring strong opioids for reducing pain intensity (SMD -0.43, 95% CI -0.52 to -0.33), low-certainty evidence for a medium between-group difference favouring tramadol for reducing pain intensity (SMD -0.55, 95% CI -0.66 to -0.44) and very low-certainty evidence for a small between-group difference favouring buprenorphine for reducing pain intensity (SMD -0.41, 95% CI -0.57 to -0.26). There was moderate-certainty evidence for a small between-group difference favouring strong opioids compared to placebo for reducing disability (SMD -0.26, 95% CI -0.37 to -0.15), moderate-certainty evidence for a small between-group difference favouring tramadol for reducing disability (SMD -0.18, 95% CI -0.29 to -0.07), and low-certainty evidence for a small between-group difference favouring buprenorphine for reducing disability (SMD -0.14, 95% CI -0.53 to -0.25). There was low-certainty evidence for a small between-group difference for an increased risk of adverse events for opioids (all types) compared to placebo; nausea (RD 0.10, 95% CI 0.07 to 0.14), headaches (RD 0.03, 95% CI 0.01 to 0.05), constipation (RD 0.07, 95% CI 0.04 to 0.11), and dizziness (RD 0.08, 95% CI 0.05 to 0.11). Antidepressants There was low-certainty evidence for no evidence of difference for antidepressants (all types) compared to placebo for reducing pain intensity (SMD -0.04, 95% CI -0.25 to 0.17) and reducing disability (SMD -0.06, 95% CI -0.40 to 0.29).

AUTHORS' CONCLUSIONS

We found no high- or moderate-certainty evidence that any investigated pharmacological intervention provided a large or medium effect on pain intensity for acute or chronic LBP compared to placebo. For acute LBP, we found moderate-certainty evidence that NSAIDs and muscle relaxants may provide a small effect on pain, and high-certainty evidence for no evidence of difference between paracetamol and placebo. For safety, we found very low- and high-certainty evidence for no evidence of difference with NSAIDs and paracetamol compared to placebo for the risk of adverse events, and moderate-certainty evidence that muscle relaxants may increase the risk of adverse events. For chronic LBP, we found low-certainty evidence that NSAIDs and very low- to high-certainty evidence that opioids may provide a small effect on pain. For safety, we found low-certainty evidence for no evidence of difference between NSAIDs and placebo for the risk of adverse events, and low-certainty evidence that opioids may increase the risk of adverse events.

Efficacy, acceptability, and safety of antidepressants for low back pain: a systematic review and meta-analysis

BACKGROUND

Antidepressant medicines are used to manage symptoms of low back pain. The efficacy, acceptability, and safety of antidepressant medicines for low back pain (LBP) are not clear. We aimed to evaluate the efficacy, acceptability, and safety of antidepressant medicines for LBP.

METHODS

We searched CENTRAL, MEDLINE, Embase, CINAHL, ClinicalTrials.gov , the EU Clinical Trials Register, and the WHO International Clinical Trial Registry Platform from inception to May 2020. We included published and trial registry reports of RCTs that allocated adult participants with LBP to receive an antidepressant medicine or a placebo medicine. Pairs of authors independently extracted data in duplicate. We extracted participant characteristics, study sample size, outcome values, and measures of variance for each outcome. We data using random-effects meta-analysis models and calculated estimates of effects and heterogeneity for each outcome. We formed judgments of confidence in the evidence in accordance with GRADE. We report our findings in accordance with the PRISMA statement. We prespecified all outcomes in a prospectively registered protocol. The primary outcomes were pain intensity and acceptability. We measured pain intensity at end-of-treatment on a 0-100 point scale and considered 10 points the minimal clinically important difference. We defined acceptability as the odds of stopping treatment for any reason.

RESULTS

We included 23 RCTs in this review. Data were available for pain in 17 trials and acceptability in 14 trials. Treatment with antidepressants decreased pain intensity by 4.33  points (95% CI - 6.15 to - 2.50) on a 0-100 scale, compared to placebo. Treatment with antidepressants increased the odds of stopping treatment for any reason (OR 1.27 [95% CI 1.03 to 1.56]), compared to placebo.

CONCLUSIONS

Treatment of LBP with antidepressants is associated with small reductions in pain intensity and increased odds of stopping treatment for any reason, compared to placebo. The effect on pain is not clinically important. The effect on acceptability warrants consideration. These findings provide Level I evidence to guide clinicians in their use of antidepressants to treat LBP.

TRIAL REGISTRATION

We prospectively registered the protocol for this systematic review on PROSPERO ( CRD42020149275 ).

Is low-dose amitriptyline effective in the management of chronic low back pain? Study protocol for a randomised controlled trial

Background

Low back pain is a major clinical and public health problem, with limited evidence-based treatments. Low-dose antidepressants are commonly used to treat pain in chronic low back pain. However, their efficacy is unproven. The aim of this pragmatic, double-blind, randomised, placebo-controlled trial is to determine whether low-dose amitriptyline (an antidepressant) is more effective than placebo in reducing pain in individuals with chronic low back pain.

Methods/design

One hundred and fifty individuals with chronic low back pain will be recruited through hospital and private medical and allied health clinics, advertising in local media and posting of flyers in community locations. They will be randomly allocated to receive either low-dose amitriptyline (25 mg) or an active placebo (benztropine mesylate, 1 mg) for 6 months. The primary outcome measure of pain intensity will be assessed at baseline, 3 and 6 months using validated questionnaires. Secondary measures of self-reported low back disability, work absence and hindrance in the performance of paid/unpaid work will also be examined. Intention-to-treat analyses will be performed.

Discussion

This pragmatic, double-blind, randomised, placebo-controlled trial will provide evidence regarding the effectiveness of low-dose antidepressants compared with placebo in reducing pain, disability, work absenteeism and hindrance in work performance in individuals with chronic low back pain. This trial has major public health and clinical importance as it has the potential to provide an effective approach to the management of chronic low back pain.

Trial registration

Australian New Zealand Clinical Trials Registry: ACTRN12612000131853; registered on 30 January 2012.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-016-1637-1) contains supplementary material, which is available to authorized users.

Evaluation of the efficacy of intrathecal injection of amitriptyline and doxepin in spinal anesthesia in comparison with bupivacaine in rats

Background:

Tricyclic antidepressants (TCAs) are commonly used orally for treating chronic pain states, such as neuropathic pain. TCAs produce analgesia by various mechanisms, including sodium channels, N-methyl-d-aspartate receptors, biogenic amines, opioids, inflammatory mediators, and substance P. Studies have shown that intrathecal tricyclic administration effectively attenuates pain and thermal hyperalgesia in inflammatory and neuropathic pain in rats.

Objectives:

The aim of this study was to evaluate the effect of two tertiary TCAs in sensory and motor block. We also used bupivacaine as a strong local anesthetic for the control group.

Materials and Methods:

In a double-blind randomized controlled trial in an animal lab, intrathecal injection of drugs was performed in 30 Wistar male rats. We divided the subjects into 3 groups: group 1: 90 µL Doxepine (50 mM), group 2: 90 µl amitriptyline (60 mM). and group 3: 90 µL bupivacaine (23 mM). Then sensory, motor, and proprioceptive changes were measured at 1, 2, 3, 4, 6, and 12 hours by one examiner.

Results:

In Groups 1 and 2, a total of 3 rats died. After adjusting the concentrations, amitriptyline had a similar potency but a longer duration of spinal blockade of motor, proprioception, and nociception than did bupivacaine (p < 0.05), whereas doxepin had a reasonable but lower efficacy and shorter duration of spinal blockade than did bupivacaine (p < 0.05). The full recovery time for Group 2 was significantly longer.

Conclusions:

It seems that tertiary amine drugs such as amitriptyline and doxepin had reasonable potencies of spinal blockade when compared to bupivacaine. However, amitriptyline had a more potent and long-acting spinal anesthetic effect. Amitriptyline may turn out to be a clinically valuable local anesthetic.

Characterization of the anticonvulsant activity of doxepin in various experimental seizure models in mice

In this paper, the anticonvulsant characteristics of doxepin were evaluated in numerous experimental seizure models, including maximal electroshock (MES)-, pentylenetetrazole (PTZ)-, isoniazid (ISO)-, 3-mercaptopropionic acid (3-MP)-, bicuculline (BIC)-, thiosemicarbazide (THIO)-, and strychnine (STR)-induced seizures. In addition, the acute adverse-effect profile of doxepin with respect to impairment of motor coordination was assessed with a mouse rotarod test. The evaluation of the time-course and dose-response relationships for doxepin provided evidence that the peak maximum anticonvulsant activity and acute adverse effects occurred 5 min after intraperitoneal (ip) administration. The results also revealed that doxepin had excellent anticonvulsant activity against maximal electroshock-induced seizures in mice with a median effect value (ED(50)) of 6.6 mg/kg. The assessment of acute adverse effects in the rotarod test revealed that doxepin induced acute neurotoxicity, and its median toxic dose (TD(50)) was 26.4 mg/kg. Additionally, doxepin showed anticonvulsant activity in several chemically-induced seizure models, including ISO, 3-MP, BIC, and THI. Based on this study, we can conclude that the antidepressant drug doxepin may be useful for treatment of depression in patients with epilepsy due to its short time to peak maximum anticonvulsant activity after ip administration (5 min) and remarkable anticonvulsant activity (6.6 mg/kg).

Antidepressants for non-specific low back pain

BACKGROUND

Antidepressants are commonly used in the management of low-back pain. However, their use is controversial.

OBJECTIVES

The aim of this review was to determine whether antidepressants are more effective than placebo for the treatment of non-specific low-back pain.

SEARCH STRATEGY

Randomised controlled trials were identified from MEDLINE and EMBASE (to September 2007), PsycINFO to June 2006, the Cochrane Central Register of Controlled Trials 2006, issue 2, and previous systematic reviews.

SELECTION CRITERIA

We included randomised controlled trials that compared antidepressant medication and placebo for patients with non-specific low-back pain, and used at least one clinically relevant outcome measure.

DATA COLLECTION AND ANALYSIS

Two blinded review authors independently extracted data and assessed the methodological quality of the trials. Meta-analyses were used to examine the effect of antidepressants on pain, depression and function, and the effect of antidepressant type on pain. To account for studies that could not be pooled, additional qualitative analyses were performed using the levels of evidence recommended by the Cochrane Back Review Group.

MAIN RESULTS

Ten trials that compared antidepressants with placebo were included in this review. The pooled analyses showed no difference in pain relief (six trials; standardized mean difference (SMD) -0.06 (95% confidence interval (CI) -0.28 to 0.16)) or depression (two trials; SMD 0.06 (95% CI -0.29 to 0.40)) between antidepressant and placebo treatments. The qualitative analyses found conflicting evidence on the effect of antidepressants on pain intensity in chronic low-back pain, and no clear evidence that antidepressants reduce depression in chronic low-back pain patients. Two pooled analyses showed no difference in pain relief between different types of antidepressants and placebo. Our findings were not altered by the sensitivity analyses which varied the level of methodological quality required for inclusion in the meta-analyses to allow data from additional trials to be examined. Two additional trials were identified in September 2007 and await assessment.

AUTHORS' CONCLUSIONS

There is no clear evidence that antidepressants are more effective than placebo in the management of patients with chronic low-back pain. These findings do not imply that severely depressed patients with back pain should not be treated with antidepressants; furthermore, there is evidence for their use in other forms of chronic pain.

Cancer pain: an update of pharmacological approaches in pain therapy

PURPOSE OF REVIEW

This review discusses clinically oriented data on advances in pharmacological research of cancer pain therapy carried out during the last year. The aim is to ascertain whether well known guidelines for cancer pain prove to be adequate or require modification.

RECENT FINDINGS

There are alternatives to morphine, which is the standard drug, including oxycodone or methadone, with the problem of equivalence doses in the case of opioid rotation. Depending on the underlying pathophysiological mechanisms, adjuvant drugs are recommended, such as antidepressants and anticonvulsants for neuropathic pain, or bisphosphonates for metastasis bone pain. Current and future research will offer receptor-specific acting new drugs or old drugs under new indications.

SUMMARY

The recommendations of the World Health Organization ladder remain the mainstay of cancer pain management. These recommendations, however, are based more on expert opinions than on evidence-based data.

Doxepin Has a Potent and Long-Acting Spinal Anesthetic Effect in Rats

Doxepin, a tricyclic antidepressant, was recently found to be effective in the treatment of various acute and chronic painful conditions. However, the mechanism of its actions was not clear, especially when involving the spine. The aim of our study was to evaluate the spinal anesthetic effect of doxepin. Two commonly used traditional local anesthetics, bupivacaine and lidocaine, were used as controls. The potencies and durations of the drugs' action were evaluated in male Sprague-Dawley rats. We found that intrathecally administered doxepin, like bupivacaine and lidocaine, produced dose-related spinal anesthetic effects on motor activity, proprioception, and nociception. Among the three drugs, doxepin produced spinal anesthetic effects in rats more potent than that of lidocaine (p < 0.001, in each comparison) and longer than that of bupivacaine and lidocaine (p < 0.001, in each comparison). The spinal activity of doxepin may provide some explanation of its clinical effect in pain management.

Pain Management in Trauma Patients

Trauma is a major cause of mortality throughout the world. In recent years, major advances have been made in the management of trauma, the end result of which has been reduced mortality and enhanced function. One of these areas is pain control. Improved pain management has not only led to increased comfort in trauma patients, but has also been shown to reduce morbidity and improve long-term outcomes. This review focuses on the treatment of pain in the setting of acute injury and on pain management in trauma patients who go on to develop chronic pain. Emphasis is placed on pharmacologic interventions, invasive and noninvasive pain management techniques, analgesia in challenging patients, and pain control in commonly encountered trauma conditions.