Buprenorphine Maintenance Subjects Are Hyperalgesic and Have No Antinociceptive Response to a Very High Morphine Dose

Hyperalgesia in Patients With a History of Opioid Use Disorder: A Systematic Review and Meta-Analysis

Importance

Short-term and long-term opioid treatment have been associated with increased pain sensitivity (ie, opioid-induced hyperalgesia). Treatment of opioid use disorder (OUD) mainly involves maintenance with methadone and buprenorphine, and observations of heightened cold pain sensitivity among patients are often considered evidence of opioid-induced hyperalgesia.

Objective

To critically examine the evidence that hyperalgesia in patients with OUD is related to opioid use.

Data Sources

Web of Science, PubMed, and Embase between March 1, 2023, and April 12, 2024, were searched.

Study Selection

Studies assessing cold pressor test (CPT) pain responses during treatment seeking, pharmacological treatment, or abstinence in patients with OUD history were included.

Data Extraction and Synthesis

Multilevel random-effects models with robust variance estimation were used for all analyses. Study quality was rated with the JBI checklist. Funnel plots and Egger regression tests were used to assess reporting bias.

Main Outcomes and Measures

Main outcomes were pain threshold, tolerance, and intensity in patients and healthy controls, and unstandardized, standardized (Hedges g), and percentage differences (%Δ) in these measures between patients and controls. The association between pain sensitivity and opioid tolerance, withdrawal, and abstinence indices was tested with meta-regression.

Results

Thirty-nine studies (1385 patients, 741 controls) met the inclusion criteria. Most studies reported CPT data on patients undergoing opioid agonist treatment. These patients had a mean 2- to 3-seconds lower pain threshold (95% CI, -4 to -1; t test P = .01; %Δ, -22%; g = -0.5) and 29-seconds lower pain tolerance (95% CI, -39 to -18; t test P < .001; %Δ, -52%; g = -0.9) than controls. Egger tests suggested that these differences may be overestimated. There were some concerns of bias due to inadequate sample matching and participant dropout. Meta-regressions yielded no clear support for hyperalgesia being opioid related.

Conclusion and Relevance

Patients receiving opioid agonist treatment for OUD are hypersensitive to cold pain. It remains unclear whether hyperalgesia develops prior to, independent of, or as a result of long-term opioid treatment. Regardless, future studies should investigate the impact of hyperalgesia on patients' well-being and treatment outcomes.

Nociceptive Flexion Reflex Threshold is No Suitable Marker for Diagnosing Opioid-Induced Hyperalgesia

Background

Opioid induced hyperalgesia (OIH) describes a state of altered pain sensation due to opioid exposure. It often occurs among persons with opioid use disorder receiving substitution therapy.

Methods

The purpose of this study was to find out, whether OIH diagnosis could be facilitated by an objective pain indicating marker: the Nociceptive Flexion Reflex (NFR). Forty persons with opioid use disorder, 20 of them maintained on methadone and 20 treated with buprenorphine, as well as a control group of 20 opioid-free subjects, were examined. It was aimed to find out whether and in which way these opioid agonists alter reflex threshold (NFR-T). A cold-pressor test was performed to investigate the prevalence of OIH. Furthermore, electrical stimulation and electromyography analyzation were used for NFR-T measurement. Subjective pain ratings were evaluated with a numeric rating scale.

Results

Significantly increased sensitivity to cold pressor pain was found in both maintenance groups when compared to their opioid-free counterparts (p < 0.001). Neither methadone nor buprenorphine showed any effect on NFR-T. This might be explained by the reflex approaching at the wrong location in the central nervous system. Consequently, NFR-T is not a suitable marker for diagnosing OIH.

Conclusion

Although methadone and buprenorphine have been proven to cause OIH, no effect on NFR-T was observed. A statistically significant effect could have been observed with a larger number of participants. Further research, with special focus on patients' adjuvant medication, should be conducted in the future, to facilitate diagnosis of OIH and provide appropriate pain management for maintenance patients.

Considerations and limitations of buprenorphine prescribing for opioid use disorder in the intensive care unit setting: A narrative review

PURPOSE

The purpose of this review is to discuss important considerations when prescribing buprenorphine for opioid use disorder (OUD) in the intensive care unit (ICU) setting, recognizing the challenges of providing detailed recommendations in the setting of limited available evidence.

SUMMARY

Buprenorphine is a partial mu-opioid receptor agonist that is likely to be increasingly prescribed for OUD in the ICU setting due to the relaxation of prescribing regulations. The pharmacology and pharmacokinetics of buprenorphine are complicated by the availability of several formulations that can be given by different administration routes. There is no single optimal dosing strategy for buprenorphine induction, with regimens ranging from very low-dose to high dose regimens. Faster induction with higher doses of buprenorphine has been studied and is frequently utilized in the emergency department. In patients admitted to the ICU who were receiving opioids either medically or illicitly, analgesia will not occur until their baseline opioid requirements are covered when their preadmission opioid is either reversed or interrupted. For patients in the ICU who are not on buprenorphine at the time of admission but have possible OUD, there are no validated tools to diagnose OUD or the severity of opioid withdrawal in critically ill patients unable to provide the subjective components of instruments validated in outpatient settings. When prescribing buprenorphine in the ICU, important issues to consider include dosing, monitoring, pain management, use of adjunctive medications, and considerations to transition to outpatient therapy. Ideally, addiction and pain management specialists would be available when buprenorphine is prescribed for critically ill patients.

CONCLUSION

There are unique challenges when prescribing buprenorphine for OUD in critically ill patients, regardless of whether they were receiving buprenorphine when admitted to the ICU setting for OUD or are under consideration for buprenorphine initiation. There is a critical need for more research in this area.

Evaluation of intervention components to maximize yoga practice among people with chronic pain taking opioid agonist therapy: A factorial experiment using the multiphase optimization strategy framework

BACKGROUND

Chronic pain affects up to half of individuals taking opioid agonist therapy (OAT; i.e., methadone and buprenorphine) for opioid use disorder (OUD), and yoga-based interventions may be useful for decreasing pain-related disability. Whereas more yoga practice (i.e., higher "dosage") may improve pain-related outcomes, it can be challenging for people with chronic pain taking OAT to attend class regularly and sustain a regular personal yoga practice. Therefore, we plan to optimize a yoga-based intervention (YBI) package in order to support class attendance and personal practice, thus maximizing the yoga dose received.

STUDY DESIGN

Using the Multiphase Optimization Strategy (MOST) framework, we will conduct a factorial experiment to examine four intervention components that may be added to a weekly yoga class as part of a YBI. Components include: 1) personal practice videos featuring study yoga teachers, 2) two private sessions with a yoga teacher, 3) daily text messages to inspire personal practice, and 4) monetary incentives for class attendance. The primary outcome will be minutes per week engaged in yoga (including class attendance and personal practice). We plan to enroll 192 adults with chronic pain who are taking OAT for OUD in this 2x2x2x2 factorial experiment.

CONCLUSION

Results of the study will guide development of an optimized yoga-based intervention package that maximizes dosage of yoga received. The final treatment package can be tested in a multisite efficacy trial of yoga to reduce pain interference in daily functioning in people with chronic pain who are taking OAT.

TRIAL REGISTRATION

Pre-registration of the study was completed on ClinicalTrials.gov (identifier: NCT04641221).

Opioid-induced analgesia among persons with opioid use disorder receiving methadone or buprenorphine: A systematic review of experimental pain studies

BACKGROUND

Treating acute pain among persons with opioid use disorder (OUD) on opioid agonist therapy (OAT) is complex, and the therapeutic benefits of opioids remain unclear when weighted against their abuse potential and respiratory depressant effects.

METHODS

We conducted a systematic review of experimental pain studies examining opioid-induced analgesia among persons with OUD on OAT. We searched multiple databases from inception to July 30, 2021. Study quality was assessed by previously established validity measures.

RESULTS

Nine studies were identified, with a total of 225 participants, of whom 63% were male, and 37% were female. Six studies included methadone-maintained persons with OUD; four studies included buprenorphine-maintained persons with OUD; and three studies included healthy persons as comparison groups. Either additional doses of OAT or other opioids - morphine, oxycodone, hydromorphone, or remifentanil - were administered. In seven studies, persons with OUD on OAT did not experience analgesia, despite receiving opioid doses up to 20 times greater than those clinically used to treat severe pain among the opioid naïve. Conversely, in two studies, high-potency opioids did produce analgesia, albeit with greater abuse potential. Notably, persons with OUD on OAT remained vulnerable to respiratory depression.

CONCLUSIONS

Although persons with OUD on OAT can derive analgesic effects from opioids, high-potency compounds may be required to achieve clinically significant pain relief. Further, persons with OUD on OAT may remain vulnerable to opioid-induced abuse potential and respiratory depression. Together, these finding have clinical, methodological, and mechanistic implications for the treatment of acute pain in the context of OAT.

Effects of opioid rotation to buprenorphine/naloxone on pain, pain thresholds, pain tolerance, and quality of life in patients with chronic pain and opioid use disorder

ABSTRACT

Long-term opioid use in patients with chronic noncancer pain (CNCP) can lead to opioid use disorder (OUD) and has been associated with hyperalgesia and reduced quality of life (QoL). Studies suggest antihyperalgesic properties of buprenorphine, and buprenorphine or naloxone (BuNa) has shown beneficial effects on QoL in patients with OUD without CNCP. This study investigated the added value of BuNa in patients with CNCP with OUD on self-reported pain, pain thresholds, pain tolerance, and QoL. In the current study, 43 outpatients with CNCP and OUD were included for inpatient conversion from full μ-receptor agonist opioids to BuNa. Self-reported pain, pain thresholds, pain tolerance, and QoL were determined at baseline and after 2 months of follow-up, using, respectively, a Visual Analogue Scale (VAS-pain and VAS-QoL), quantitative sensory testing, and EuroQol-5 dimensions. In total, 37 participants completed the protocol, and their data were analyzed. The mean VAS-pain score decreased from 51.3 to 37.2 (27.5%, F = 3.3; P = 0.044), whereas the pressure pain threshold and electric pain threshold or tolerance increased after substitution (F = 7.8; P = 0.005 and F = 44.5; P < 0.001, respectively), as well as QoL (EuroQol-5 dimensions questionnaire: F = 10.4; P = 0.003 and VAS-QoL: F = 4.4; P = 0.043). We found that conversion of full μ-receptor agonists to BuNa, in patients with CNCP with OUD, was accompanied with lower self-reported pain, higher pain thresholds, higher pain tolerance, and improved QoL. Despite several study limitations, these data suggest that BuNa might be of value in patients with CNCP with OUD. Future studies should investigate long-term effects of BuNa in randomized trials.

Attitudes Towards and Management of Opioid-induced Hyperalgesia: A Survey of Chronic Pain Practitioners

OBJECTIVES

Opioid-induced hyperalgesia (OIH) is a phenomenon whereby opioids increase patients' pain sensitivity, complicating their use in analgesia. We explored practitioners' attitudes towards, and knowledge concerning diagnosis, risk factors, and treatment of OIH.

MATERIALS AND METHODS

We administered an 18-item cross-sectional survey to 850 clinicians that managed chronic pain with opioid therapy.

RESULTS

The survey response rate was 37% (318/850). Most respondents (240/318, 76%) reported they had observed patients with OIH in their practice, of which 38% (84/222) reported OIH affected >5% of their chronic pain patients. The majority (133/222, 60%) indicated that OIH could result from any dose of opioid therapy. The most commonly endorsed chronic pain conditions associated with the development of OIH were fibromyalgia (109/216, 51%) and low back pain (91/216, 42%), while 42% (91/216) indicated that no individual chronic pain condition was associated with greater risk of OIH. The most commonly endorsed opioids associated with the development of OIH were oxycodone (94/216, 44%), fentanyl (86/216, 40%), and morphine (84/216, 39%); 27% (59/216) endorsed that no specific opioid was more likely to result in OIH. Respondents commonly managed OIH by opioid dose reduction (147/216, 68%), administering a nonopioid adjuvant (133/216, 62%), or discontinuing opioids (95/216, 44%).

DISCUSSION

Most clinicians agreed that OIH is a complication of opioid therapy, but were divided regarding the prevalence of OIH, etiological factors, and optimal management.

Pharmacological treatment of pain among persons with opioid addiction: A systematic review and meta-analysis with implications for drug development

The clinical features and neurobiology of pain and opioid use disorder (OUD) are inextricably linked. Despite emerging evidence supporting the negative impact of ongoing pain in the treatment of OUD, the pharmacological management of pain in the presence of OUD has received limited attention. We sought to systematically review the studies investigating pharmacotherapies for pain among persons with OUD. Eligible studies had participants with OUD and outcomes including evoked or spontaneous pain. We searched Scopus, Cochrane Database of Systematic Reviews, Medline, and Embase. Out of 1,097 studies that met the search criteria, 12 studies provided data relevant to the research question-five laboratory studies and seven clinical trials. Random effects pooled estimates suggested no significant difference between groups at baseline but a response favoring the active treatment group over placebo, with nonsignificant heterogeneity between studies. Findings from these studies provide preliminary evidence for analgesic and antihyperalgesic effects of gabapentin, GABA agonists, and NMDA antagonists among persons with OUD. To establish the tradeoffs between the analgesic effects and abuse liability of these compounds, further well-controlled clinical trials are required among persons with OUD. This review also underscores the need for methodological enhancement in drug development for pain in OUD. Future research should address the clinical and neurobiological overlap between pain- and addiction-related phenomena. Transdisciplinary approaches may identify biomarkers of these shared phenomena and their neural substrates. The development of novel therapeutics for pain in OUD may be accelerated by such integration of pain and addiction research.

Endogenous opiates and behavior: 2019

This paper is the forty-second consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2019 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

The thermal antinociceptive effects of a high-concentration formulation of buprenorphine alone or followed by hydromorphone in conscious cats

OBJECTIVE

To evaluate the thermal antinociceptive effects of a high-concentration formulation of buprenorphine alone or followed by hydromorphone in conscious cats.

STUDY DESIGN

Randomized, blinded, placebo-controlled crossover study design.

ANIMALS

A total of six purpose-bred, adult female ovariohysterectomized Domestic Short Hair cats.

METHODS

Cats were allocated into three treatments each consisting of two injections, subcutaneous then intravenous (IV) administration, 2 hours apart: treatment SS, two injections of 0.9% saline; treatment BS, buprenorphine (0.24 mg kg^-1, 1.8 mg mL^-1) and saline; and treatment BH, buprenorphine (0.24 mg kg^-1) and hydromorphone (0.1 mg kg^-1). Skin temperature (ST) and thermal threshold (TT) were recorded before (baseline) and for 24 hours following first injection. TT data were analyzed using mixed linear models and a Benjamini-Hochberg sequential adjustment procedure (p < 0.05).

RESULTS

There were no significant differences among treatments for baseline ST and TT values, treatment SS over time and between treatments BS and BH. Compared with baseline, TT was significantly increased at all time points in treatments BH and BS except at 2 hours in treatment BS. TT was significantly higher than SS at 3-18 hours and 4-12 hours for treatments BS and BH, respectively. Maximal increases in TT were 47.5 °C at 2 hours, 53.9 °C at 3 hours and 52.4 °C at 6 hours in treatments SS, BS and BH, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

Administration of IV hydromorphone following high-concentration buprenorphine provided no additional antinociception and decreased the duration of effect when compared with high-concentration buprenorphine alone. Alternative analgesics should be considered if additional analgesia is required after administration of high-concentration buprenorphine.

Prevalence, Characteristics, and Management of Chronic Noncancer Pain Among People Who Use Drugs: A Cross-Sectional Study

INTRODUCTION

Most studies on chronic noncancer pain (CNCP) in people who use drugs (PWUD) are restricted to people attending substance use disorder treatment programs. This study assessed the prevalence of CNCP in a community-based sample of PWUD, identified factors associated with pain, and documented strategies used for pain relief.

METHODS

This was a cross-sectional study nested in an ongoing cohort of PWUD in Montreal, Canada. Questionnaires were administered to PWUD seen between February 2017 and January 2018. CNCP was defined as pain lasting three or more months and not associated with cancer.

RESULTS

A total of 417 PWUD were included (mean age = 44.6 ± 10.6 years, 84% men). The prevalence of CNCP was 44.8%, and the median pain duration (interquartile range) was 12 (5-18) years. The presence of CNCP was associated with older age (>45 years old; odds ratio [OR] = 1.8, 95% CI = 1.2-2.7), male sex (OR = 2.3, 95% CI = 1.2-4.2), poor health condition (OR = 1.9, 95% CI = 1.3-3.0), moderate to severe psychological distress (OR = 2.9, 95% CI = 1.8-4.7), and less frequent cocaine use (OR = 0.5, 95% CI = 0.3-0.9). Among CNCP participants, 20.3% used pain medication from other people, whereas 22.5% used alcohol, cannabis, or illicit drugs to relieve pain. Among those who asked for pain medication (N = 24), 29.2% faced a refusal from the doctor.

CONCLUSIONS

CNCP was common among PWUD, and a good proportion of them used substances other than prescribed pain medication to relieve pain. Close collaboration of pain and addiction specialists as well as better pain assessment and access to nonpharmacological treatments could improve pain management in PWUD.

Perioperative Management of Buprenorphine: Solving the Conundrum

OBJECTIVE

There is no consensus on the optimal perioperative management of patients on buprenorphine (BUP) for opioid use disorder (OUD). This article will review the available literature on BUP and the analgesic efficacy of BUP combined with full mu-opioid agonists and discuss the conflicting management strategies in the context of acute pain and our institution's protocol for the periprocedural management of BUP.

METHODS

We searched published data on BUP periprocedural management from inception through March 2018 without language restrictions. Study selection included publications reporting outcomes on perioperative pain management in OUD patients maintained on BUP.

RESULTS

Our search resulted in four case reports supporting periprocedural discontinuation of BUP and two case series, one secondary observational study, one prospective matched cohort study, and four retrospective cohort studies supporting periprocedural continuation of BUP. No clinical trials were identified.

CONCLUSIONS

Maintaining BUP perioperatively does not lead to worsened clinical outcomes. Patients can receive adequate pain control from mu-opioid agonists while maintained on BUP. Based upon available evidence, we recommend continuing BUP at a reduced dose when indicated to avoid withdrawal symptoms and to facilitate the analgesic efficacy of mu-opioid agonists administered in combination for acute postoperative pain.

Efficacy of multimodal analgesic treatment of severe traumatic acute pain in mice pretreated with chronic high dose of buprenorphine inducing mechanical allodynia

Managing severe acute nociceptive pain in buprenorphine-maintained individuals for opioid use disorder management is challenging owing to the high affinity and very slow dissociation of buprenorphine from μ-opioid receptors that hinders the use of full agonist opioid analgesics. In a translational approach, the aim of this study was to use an animal setting to investigate the effects of a chronic high dose of buprenorphine treatment on nociceptive thresholds before and after applying a severe acute nociceptive traumatic surgery stimulus and to screen postoperative pharmacological analgesic strategies. A chronic treatment of mice with a high dose of buprenorphine (BUP HD, 2 × 200 μg/kg/day; i.p.) revealed significant mechanical allodynia. One and two days after having discontinued buprenorphine administration and having induced a severe nociceptive acute pain by a closed tibial fracture, acute administration of morphine at a dose which has analgesic effects in absence of pretreatment (4.5 mg/kg; i.p.), was ineffective to reduce pain in the BUP HD group. However, mimicking multimodal analgesia strategy used in human postoperative context, the combination of morphine (administered at the same dose) with a NMDA receptor antagonist (ketamine) or an NSAID (ketoprofen) produced antinociceptive responses in these animals. The mouse model of closed tibial fracture could be useful to identify analgesic strategies of postoperative pain for patients with chronic exposure to opioids and suffering from hyperalgesia.

Perceptions of long-acting reversible contraception among women receiving medication for opioid use disorder in Vermont

OBJECTIVES

To evaluate perceptions of long-acting reversible contraceptives (LARC) among women receiving medication for opioid use disorder.

STUDY DESIGN

Cross-sectional survey of 200 women receiving medication for opioid use disorder in Vermont.

RESULTS

A considerable proportion of women receiving medication for opioid use disorder in Vermont reported previous use of an IUD (40%) and/or a subdermal contraceptive implant (16%); the majority of prior LARC users were satisfied with their IUD (68%) or their implant (74%). Of the 38% of participants who had never considered IUD use, 85% percent (64/75) said that they knew nothing or only a little about IUDs. Of the 61% of participants who had never considered an implant, 81% percent (98/121) said that they knew nothing or only a little about the contraceptive method. The most commonly reported reasons for a lack of interest in the IUD and/or implant were concerns about side effects and preference for a woman-controlled method.

CONCLUSIONS

Gaps in LARC knowledge are common among those who have not used LARCs and concerns about side effects and preferences for a woman-controlled method limit some women's interest in these contraceptives. Additionally, reasons for dissatisfaction among past users are generally similar for IUD and implant and include irregular bleeding and having a bad experience with the method.

IMPLICATIONS

Efforts to increase awareness of LARC methods among women receiving medication for opioid use disorder should address concerns about side effects and reproductive autonomy and encourage satisfied LARC users to share their experiences with their social networks.

Long-term naturalistic follow-up of chronic pain in adults with prescription opioid use disorder

BACKGROUND

Chronic pain is common in patients with prescription opioid use disorder (OUD), and pain severity has been shown to predict opioid use for those with chronic pain. However, recent research suggests that focusing on pain status (i.e., the presence or absence of chronic pain) at treatment initiation may not reflect the clinical significance of pain over the long-term course of OUD. Reports of variability in chronic pain and its clinical significance over time have yet to be investigated in patients with prescription OUD. The present study examined variability in chronic pain status from entry into prescription OUD treatment through 3.5-year follow-up. Additionally, we examined the association between concurrent chronic pain and opioid use at three follow-up time points.

METHODS

This secondary analysis (N = 309) of a national, randomized, controlled trial of prescription OUD treatment used generalized estimating equations to assess variability in the prevalence of chronic pain from study entry to 3.5-year follow-up, and the association between chronic pain status and concurrent opioid use.

RESULTS

Fifty-three percent of participants reported variability in chronic pain status over time. The prevalence of chronic pain decreased from study entry through follow-up (aOR = 0.47, p < 0.001). Chronic pain was associated with increased opioid use at each follow-up assessment (aOR = 3.56, p < 0.001).

CONCLUSIONS

Chronic pain status may vary over time in those with prescription OUD, and chronic pain appears to be associated with concurrent opioid use. The present findings highlight the importance of assessing chronic pain throughout the course of prescription OUD.

A pilot study assessing acceptability and feasibility of hatha yoga for chronic pain in people receiving opioid agonist therapy for opioid use disorder

The purpose of this project was to assess the feasibility and acceptability of a hatha yoga program designed to target chronic pain in people receiving opioid agonist therapy for opioid use disorder. We conducted a pilot randomized trial in which people with chronic pain who were receiving either methadone maintenance therapy (n = 20) or buprenorphine (n = 20) were randomly assigned to weekly hatha yoga or health education (HE) classes for 3 months. We demonstrated feasibility in many domains, including recruitment of participants (58% female, mean age 43), retention for follow-up assessments, and ability of teachers to provide interventions with high fidelity to the manuals. Fifty percent of participants in yoga (95% CI: 0.28-0.72) and 65% of participants in HE (95% CI: 0.44-0.87) attended at least 6 of 12 possible classes (p = 0.62). Sixty-one percent in the yoga group reported practicing yoga at home, with a mean number of times practicing per week of 2.67 (SD = 2.37). Participant mood improved pre-class to post-class, with greater decreases in anxiety and pain for those in the yoga group (p < 0.05). In conclusion, yoga can be delivered on-site at opioid agonist treatment programs with home practice taken up by the majority of participants. Future research may explore ways of increasing the yoga "dosage" received. This may involve testing strategies for increasing either class attendance or the amount of home practice or both.

Acute Experimental Pain Responses in Methadone- and Buprenorphine/Naloxone-Maintained Patients Administered Additional Opioid or Gabapentin: A Double-Blind Crossover Pilot Study

Objective

The study objective was to identify the analgesic efficacy of three different pharmacological strategies in patients receiving methadone or buprenorphine as opioid agonist treatment (OAT). The three pharmacological approaches, a) increasing maintenance methadone/buprenorphine dose by 30%, b) adding oxycodone, or c) adding a single dose of gabapentin, were compared with a control condition of the participant’s usual OAT dose.

Design

A randomized, controlled, double-blinded, double-dummy, within-subject crossover study.

Subjects

Nine participants on stable doses of methadone and eight participants on stable doses of buprenorphine were recruited.

Setting

An outpatient opioid treatment clinic in inner city Sydney, Australia.

Methods

The cold pressor tolerance test was used to examine experimental pain threshold and tolerance. Ratings of subjective drug effects and safety measures (physiological and cognitive) were assessed.

Results

There was no difference in the primary outcome measures of pain thresholds or tolerance between the conditions examined. Interindividual variability was evident. Differences in some subjective measures were identified, including lower pain recall, lower “bad effects,” and higher global satisfaction in the additional methadone condition. In the buprenorphine arm, increased drug liking and “bad effects” were detected with oxycodone administration, while increased subjective intoxication was identified with gabapentin.

Conclusions

There was no evidence of an objective improvement in analgesia with any condition compared with control. Further research is required to optimize pain management strategies in this population.

A Retrospective Survey of Buprenorphine Substitute Treatment With Minimal Dosage in Heroin Use Disorder

Objectives: It is widely accepted that buprenorphine maintenance treatment (BMT) with dosages above 8 mg daily is effective for patients with heroin use disorder. In this study, the authors evaluated the effectiveness of long-term BMT for heroin users in China, with dosages kept on a much smaller level. Methods: This is a retrospective observational study of 72 patients who had undergone detoxification and continued with buprenorphine maintenance between 2007 and 2016. Measurements such as self-reported relapse status, buprenorphine doses, protracted symptoms, general health condition, and self-reported side effects were included. Results: At the time of interview, 51 patients had remained abstinent at follow-up (including 13 who were opioid-free). The dosages of buprenorphine were 1.33 ± 0.88 (ranging 0.3-3.5) mg/day when maintenance treatment was initiated and 1.2 ± 0.8 (ranging 0.2-3.2) mg/day at the last follow-up. The remaining patients had either relapsed on heroin (n = 11) or switched to compulsory treatment (n=10). In general, abstinent patients had minimal protracted symptoms, especially in physical symptoms. Opioid-free abstainers were more likely to report good physical health than patients on buprenorphine. Predictors of worse outcomes (relapsed or switched to compulsory treatment) were lower education levels, younger age, and younger onset of illicit drug use. Conclusions: This study shows promising results of minimal-dosage BMT in treating heroin use disorder. We recommend further studies applying minimal-dosage BMT in China and worldwide.

Buprenorphine: Therapeutic potential beyond substance abuse

Discussion of buprenorphine and its potential utility for the treatment of inflammatory disorders.