Intraoperative methadone: rediscovery, reappraisal, and reinvigoration?

Hypoxic brain damage in Methadone misuse: insights from MRI imaging and comparative study

BACKGROUND

This study aimed to investigate the potential presence of brain disorders, particularly hypoxia, via magnetic resonance imaging (MRI) in patients misusing methadone, with a comparison to regular opium users and a control group.

METHODS

Conducted as a cross-sectional comparative study at Kamali Hospital in Karaj, Iran, the research included male participants comprising methadone users, opium users, and controls. Inclusion criteria were stringent, focusing on substance use duration and absence of brain structural disorders. MRI scans were performed using a 1.5T MRI scanner. Qualitative MRI assessments and chi-square tests analyzed associations between substance use and hypoxia, while logistic regression examined potential confounding variables.

RESULTS

Significant hypoxia was observed in the methadone group (16.7%, 5/24; p = 0.00057), with no cases in the opium or control groups. Logistic regression analysis showed no significant predictors of hypoxia regarding dose and duration of use. MRI findings in methadone users with hypoxia included varied ADC intensities, high signal intensities on T2-weighted and diffusion-weighted imaging (DWI) sequences, and angiogenesis patterns on TOF sequences. The co-use of methadone and alcohol was noted in three of the five hypoxia cases.

CONCLUSION

Methadone misuse, particularly with alcohol, poses a significant risk of hypoxia, detectable via MRI. This study underscores the need for routine MRI monitoring, stricter regulation of non-prescribed methadone, and enhanced public health education to mitigate misuse risks. Future research should expand sample sizes and incorporate advanced imaging techniques to further elucidate methadone's neurological impact.

Respiratory Depression Following Intraoperative Methadone: A Retrospective Cohort Study

BACKGROUND

Methadone is used as a perioperative analgesic in the management of postoperative pain. Despite positive outcomes from randomized trials favoring methadone, concerns about its safety persist, particularly regarding respiratory depression (RD) and excessive sedation. In this study, we compared the incidence of naloxone administration between patients administered intraoperative methadone and those administered intraoperative morphine as a measure of severe RD. Time spent at the postanesthesia care unit (PACU) was used as a proxy variable for excessive sedation.

METHODS

This was a retrospective cohort study including all patients aged ≥18 years who underwent surgery between March 2019 and March 2023 at Aarhus University Hospital, Denmark. We assessed the association between intraoperative administration of either methadone or morphine and postoperative naloxone administration within the first 24 hours using logistic regression (primary outcome). An analogous linear regression model was used for the secondary outcome of time spent in the PACU after surgery. Patients were weighted using propensity scores to adjust for potential confounding variables.

RESULTS

A total of 14,522 patients were included in the analysis. Among the 2437 patients who received intraoperative methadone, 15 (0.62%) patients received naloxone within the first 24 hours after surgery compared to 68 of 12,0885 (0.56%) who received intraoperative morphine. No statistical difference was observed in the odds of naloxone administration between patients administered methadone or morphine (adjusted odds ratio 95% confidence interval [CI], 1.21 [0.40-2.02]). Patients who were administered intraoperative methadone had a mean PACU length of stay (LOS) of 334 minutes (standard deviation [SD], 382) compared to 195 minutes (SD, 228) for those administered intraoperative morphine. The adjusted PACU LOS of patients administered intraoperative methadone was 26% longer compared to those administered intraoperative morphine (adjusted ratio of the geometric means 95% CI, 1.26 [1.22-1.31]).

CONCLUSIONS

The incidence of naloxone administration to treat severe RD was low. No difference was observed in the odds of naloxone administration to treat severe RD between patients administered intraoperative methadone or intraoperative morphine. Intraoperative methadone was associated with longer stays at the PACU; however, this result should be interpreted with care. Our findings suggest that intraoperative methadone has a safety profile comparable to that of morphine with regard to severe RD.

Perioperative Methadone for Spine Surgery: A Scoping Review

Complex spine surgery is associated with significant acute postoperative pain. Methadone possesses pharmacological properties that make it an attractive analgesic modality for major surgeries. This scoping review aimed to summarize the evidence for the perioperative use of methadone in adults undergoing complex spine surgery. The review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR). A search was performed using MEDLINE, CINAHL, Cochrane Library, Scopus, Embase, and Joanna Briggs between January 1946 and April 2023. The initial search identified 317 citations, of which 12 met the criteria for inclusion in the review. There was significant heterogeneity in the doses, routes of administration, and timing of perioperative methadone administration in the included studies. On the basis of the available literature, methadone has been associated with reduced postoperative pain scores and reduced postoperative opioid consumption. Though safety concerns have been raised by observational studies, these have not been confirmed by prospective randomized studies. Further research is required to explore optimal methadone dosing regimens, the potential synergistic relationships between methadone and other pharmacological adjuncts, as well as the potential long-term antinociceptive benefits of perioperative methadone administration.

Pharmacokinetics of Methadone in Adult Patients Undergoing Cardiac Surgery With Cardiopulmonary Bypass

BACKGROUND

Cardiopulmonary bypass (CPB) induces profound physiological changes that may alter the pharmacokinetics of methadone. We aimed to describe the pharmacokinetics of an intravenous bolus of methadone racemate in adult patients undergoing heart surgery with CPB.

METHODS

We prospectively studied 29 patients aged 45 to 75 years scheduled for cardiac surgery with CPB who received methadone 0.2 mg/kg after anesthesia induction. Arterial blood samples (n = 10) were taken, before, during, and after CPB. Pharmacokinetic analysis was undertaken using nonlinear mixed effects models.

RESULTS

All patients completed the study. The median [interquartile range] methadone concentrations decreased from 34.8 [23.9-48.2] ng/mL (10 minutes before CPB) to 18.2 [9.9-26] ng/mL after 60 minutes of CPB (P < .001). A 3-compartment model adequately described the observed changes in methadone concentrations. The influence of CPB on methadone pharmacokinetics was best described by hemodilution in a fixed volume of 1.5 L (CPB circuit volume) and by sequestration from the CPB components (CLSEQ = 93.4 L/h, 95%CI 59-124, P < .01). The observed effect of CPB in methadone pharmacokinetics can be compensated by giving a supplementary bolus dose of 0.05 mg/kg at the end of CPB.

CONCLUSIONS

Our results confirmed a decay in methadone concentrations during CPB, which, in our modeling analysis, was attributed to hemodilution and sequestration within the CPB components.

Intraoperative Methadone in Spine Surgery ERAS Protocols: A Systematic Review of the Literature

STUDY DESIGN

Systematic review.

OBJECTIVE

To systematically review the use of intraoperative methadone in spine surgery and examine its effects on postoperative opioid use, pain, length of stay, and operative time.

SUMMARY OF BACKGROUND DATA

Spine surgery patients commonly have a history of chronic pain and opioid use, and as a result, they are at an increased risk of severe postoperative pain. While pure mu opioids remain the standard for acute surgical pain management, they are associated with significant short-term and long-term adverse events. Methadone presents an alternative to pure mu opioids which may improve postoperative management of pain following intraoperative use.

METHODS

A systematic review of MEDLINE, Embase, and Web of Science databases was conducted to review existing literature detailing operating time, postoperative pain, opioid usage, and hospital length of stay (LOS) following intraoperative methadone administration in spine surgery.

RESULTS

Following screening of 994 articles and application of inclusion criteria, 8 articles were included, 4 of which were retrospective. Conventional spine surgery intraoperative analgesic strategies used as comparators for intraoperative methadone included hydromorphone, ketamine, and sufentanil. Considering patient outcomes, included studies observed that patients treated with intraoperative methadone had statistically similar or significantly reduced pain scores, opioid usage, and LOS compared with comparator analgesics. However, one study observed that intraoperative methadone used in a multimodal analgesia regimen strategy with ketamine resulted in a shortened LOS compared with the use of intraoperative methadone alone. Differences in operating time between cases that used intraoperative methadone and cases that used comparator analgesics were not statistically significant among included studies.

CONCLUSION

Methadone may present an alternative option for both intraoperative and postoperative analgesia in spine surgery recovery protocols and may reduce postoperative pain, opioid use, and LOS while maintaining consistent operating time and reduced side effects of pure mu opioids.

LEVEL OF EVIDENCE

Level II.

Intraoperative somatosensory evoked potential (SEP) monitoring: an updated position statement by the American Society of Neurophysiological Monitoring

Somatosensory evoked potentials (SEPs) are used to assess the functional status of somatosensory pathways during surgical procedures and can help protect patients' neurological integrity intraoperatively. This is a position statement on intraoperative SEP monitoring from the American Society of Neurophysiological Monitoring (ASNM) and updates prior ASNM position statements on SEPs from the years 2005 and 2010. This position statement is endorsed by ASNM and serves as an educational service to the neurophysiological community on the recommended use of SEPs as a neurophysiological monitoring tool. It presents the rationale for SEP utilization and its clinical applications. It also covers the relevant anatomy, technical methodology for setup and signal acquisition, signal interpretation, anesthesia and physiological considerations, and documentation and credentialing requirements to optimize SEP monitoring to aid in protecting the nervous system during surgery.

Single-dose Intraoperative Methadone for Pain Management in Pediatric Tonsillectomy: A Randomized Double-blind Clinical Trial

BACKGROUND

More than 500,000 elective tonsillectomies are performed in U.S. children annually. Pain after pediatric tonsillectomy is common, often severe, and undertreated. There is no consensus on the optimal management of perioperative tonsillectomy pain. Methadone, with an elimination half-life of 1 to 2 days, has a longer duration of effect than short-duration opioids such as fentanyl. The primary objective of this study was to investigate the intraoperative use of methadone for pediatric tonsillectomy. It tested the hypothesis that methadone would result in less postoperative opioid use compared with short-duration opioids in children after tonsillectomy.

METHODS

This double-blind, randomized, parallel group trial in children (3 to 17 yr) undergoing tonsillectomy compared single-dose intravenous methadone (0.1 mg/kg then 0.15 mg/kg age-ideal body weight, in a dose escalation paradigm) versus as-needed short-duration opioid (fentanyl) controls. Opioid use, pain, and side effects were assessed in-hospital and 7 days postoperatively via electronic surveys. The primary outcome was total 7-day opioid use in oral morphine equivalents per kilogram (kg). Secondary outcomes were opioid use in the postanesthesia care unit, daily pain scores, and total number of 7-day opioid doses used.

RESULTS

Data analysis included 60 children (20/group), age 5.9 ± 3.7 yr (mean ± SD; median, 4; range, 3 to 17). Total 7-day opioid use (oral morphine equivalents per kg median [interquartile range]) was 1.5 [1.2, 2.1] in controls, 0.9 [0.1, 1.4] after methadone 0.1 mg/kg (P = 0.045), and 0.5 [0, 1.4] after methadone 0.15 mg/kg (P = 0.023). Postanesthesia care unit opioid use (oral morphine equivalents per kg) in controls was 0.15 [0.1, 0.3], 0.04 [0, 0.1] after methadone 0.1 mg/kg (P = 0.061). and 0.0 [0, 0.1] after methadone 0.15 mg/kg (P = 0.021). Postoperative pain scores were not different between groups. No serious opioid-related adverse events occurred.

CONCLUSIONS

This small initial study in children undergoing tonsillectomy found that single-dose intraoperative methadone at 0.15 mg/kg age ideal body weight was opioid-sparing compared with intermittent fentanyl.

EDITOR’S PERSPECTIVE

The Effects of Intraoperative Methadone on Postoperative Pain Control in Pediatric Patients: A Scoping Review

Inadequate perioperative pain control has deleterious effects on children's development and can lead to heightened pain experiences and the avoidance of future medical procedures. Reports of perioperative use of methadone in children are increasing, as it has a favorable pharmacodynamic profile; however, the effectiveness of methadone in reducing postoperative pain has not been established. We, therefore, aimed to provide a scoping review of the literature comparing the effect of intraoperative methadone versus other opioids on postoperative opioid consumption, pain scores, and adverse events in pediatric patients. We identified studies in PubMed, Scopus, Embase, and Cumulative Index to Nursing and Allied Health Literature (CINAHL) databases from inception to January 2023. Postoperative opioid consumption, pain scores, and adverse events were extracted for analysis. We screened 1864 studies, of which 83 studies were selected for full-text review. Five studies were included in the final analysis. Postoperative opioid consumption was decreased overall in children who received methadone compared to those who did not. The majority of studies indicated that methadone was superior to other opioids in reported pain scores, while the frequency of adverse events was similar between the groups. Although the data reviewed highlight a potential benefit of intraoperative methadone in pediatric patients, 4 of the 5 studies had serious methodological concerns. Thus, we cannot make strong recommendations for the regular use of methadone in the perioperative setting at this time. Our results highlight the need for large, well-designed randomized trials to fully evaluate the safety and efficacy of intraoperative methadone in diverse pediatric surgical populations.

Intraoperative Methadone Use Is Associated With Reduced Postoperative Pain and More Rapid Opioid Weaning After Coronary Artery Bypass Grafting

OBJECTIVE

To explore the association between intraoperative methadone use, postoperative pain, and opioid consumption after coronary artery bypass grafting (CABG) surgery.

DESIGN

Retrospective cohort study.

SETTING

Single academic medical center.

PARTICIPANTS

Patients undergoing isolated CABG over a 5-year period.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Demographic data, comorbidities, and intraoperative anesthetic medications were recorded. Primary study outcomes were average and maximum pain scores and morphine milligram equivalent consumption on the first 2 postoperative days (PODs). Linear mixed-effects regression models were used to examine the effect of intraoperative methadone use on study outcomes. Among 1,338 patients, 78.6% received intraoperative methadone (0.2 mg/kg). Patients who did not receive methadone had higher average (estimated [Est], 0.48; 95% confidence interval [CI], 0.22-0.73; p < 0.001) and maximum postoperative (Est, 0.49; 95% CI, 0.23-0.75; p < 0.001) pain scores over PODs 0 to 2. For postoperative opioid consumption, there was a significant intraoperative methadone use-time interaction effect on postoperative opioid use (odds ratio [OR], 2.21; 95% CI, 1.74-2.80; p < 0.001). Across PODs 0 to 2, patients who received intraoperative methadone had a faster decline in postoperative opioid use than those who did not receive intraoperative methadone. Patients who did not receive intraoperative methadone were extubated slightly faster (OR, 0.82; 95% CI, 0.72-0.93; p < 0.01).

CONCLUSIONS

Our data suggest that the use of intraoperative methadone is safe, reduces postoperative pain, and expedites weaning from postoperative opioids after CABG surgery.

Opioid use disorder in pediatric populations: considerations for perioperative pain management and precision opioid analgesia

INTRODUCTION

Opioids are commonly used for perioperative analgesia, yet children still suffer high rates of severe post-surgical pain and opioid-related adverse effects. Persistent and severe acute surgical pain greatly increases the child's chances of chronic surgical pain, long-term opioid use, and opioid use disorder.

AREAS COVERED

Enhanced recovery after surgery (ERAS) protocols are often inadequate in treating a child's severe surgical pain. Research suggests that 'older' and longer-acting opioids such as methadone are providing better methods to treat acute post-surgical pain. Studies indicate that lower repetitive methadone doses can decrease the incidence of chronic persistent surgical pain (CPSP). Ongoing research explores genetic components influencing severe surgical pain, inadequate opioid analgesia, and opioid use disorder. This new genetic research coupled with better utilization of opioids in the perioperative setting provides hope in personalizing surgical pain management, reducing pain, opioid use, adverse effects, and helping the fight against the opioid pandemic.

EXPERT OPINION

The opioid and analgesic pharmacogenomics approach can proactively 'tailor' a perioperative analgesic plan to each patient based on underlying polygenic risks. This transition from population-based knowledge of pain medicine to individual patient knowledge can transform acute pain medicine and greatly reduce the opioid epidemic's socioeconomic, personal, and psychological strains globally.

Preoperative Alcohol Use, Postoperative Pain, and Opioid Use After Coronary Artery Bypass Surgery

OBJECTIVES

Chronic alcohol use is associated with chronic pain and increased opioid consumption. The association between chronic alcohol use and acute postoperative pain has been studied minimally. The authors' objective was to explore the association among preoperative alcohol use, postoperative pain, and opioid consumption after coronary artery bypass grafting (CABG).

DESIGN

A retrospective cohort study.

SETTING

At a single academic medical center.

PARTICIPANTS

Patients having isolated CABG.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Demographics, comorbidities, and baseline alcohol consumption were recorded. Primary outcomes were mean pain score and morphine milligram equivalent (MME) consumption on postoperative day 0. Among 1,338 patients, there were 764 (57.1%) who had no weekly preoperative alcohol use, 294 (22.0%) who drank ≤1 drink per week, 170 (12.7%) who drank 2-to-7 drinks per week, and 110 (8.2%) who drank 8 or more drinks per week. There was no significant difference in mean pain score on postoperative day 0 in patients who consumed different amounts of alcohol (no alcohol = 5.3 ± 2.2, ≤1 drink = 5.2 ± 2.1, 2 to 7 drinks = 5.3 ± 2.3, 8 or more drinks = 5.4 ± 1.9, p = 0.66). There was also no significant difference in median MME use on postoperative day 0 in patients who consumed different amounts of alcohol (no alcohol = 22.5 mg, ≤1 drink = 21.1 mg, 2-to-7 drinks = 24.8 mg, 8 or more drinks = 24.5 mg, p = 0.14).

CONCLUSIONS

There is no apparent association among mild-to-moderate preoperative alcohol consumption and early postoperative pain and opioid use in patients who underwent CABG.

Natural Products Inhibition of Cytochrome P450 2B6 Activity and Methadone Metabolism

Methadone is cleared predominately by hepatic cytochrome P450 (CYP) 2B6-catalyzed metabolism to inactive metabolites. CYP2B6 also catalyzes the metabolism of several other drugs. Methadone and CYP2B6 are susceptible to pharmacokinetic drug-drug interactions. Use of natural products such as herbals and other botanicals is substantial and growing, and concomitant use of prescription medicines and non-prescription herbals is common and may result in interactions, often precipitated by CYP inhibition. Little is known about herbal product effects on CYP2B6 activity, and CYP2B6-catalyzed methadone metabolism. We screened a family of natural product compounds used in traditional medicines, herbal teas, and synthetic analogs of compounds found in plants, including kavalactones, flavokavains, chalcones and gambogic acid, for inhibition of expressed CYP2B6 activity and specifically inhibition of CYP2B6-mediated methadone metabolism. An initial screen evaluated inhibition of CYP2B6-catalyzed 7-ethoxy-4-(trifluoromethyl) coumarin O-deethylation. Hits were further evaluated for inhibition of racemic methadone metabolism, including mechanism of inhibition and kinetic constants. In order of decreasing potency, the most effective inhibitors of methadone metabolism were dihydromethysticin (competitive, K i 0.074 µM), gambogic acid (noncompetitive, K i 6 µM), and 2,2'-dihydroxychalcone (noncompetitive, K i 16 µM). Molecular modeling of CYP2B6-methadone and inhibitor binding showed substrate and inhibitor binding position and orientation and their interactions with CYP2B6 residues. These results show that CYP2B6 and CYP2B6-catalyzed methadone metabolism are inhibited by certain natural products, at concentrations which may be clinically relevant. SIGNIFICANCE STATEMENT: This investigation identified several natural product constituents which inhibit in vitro human recombinant CYP2B6 and CYP2B6-catalyzed N-demethylation of the opioid methadone. The most potent inhibitors (K i) were dihydromethysticin (0.074 µM), gambogic acid (6 µM) and 2,2'-dihydroxychalcone (16 µM). Molecular modeling of ligand interactions with CYP2B6 found that dihydromethysticin and 2,2'-dihydroxychalcone bound at the active site, while gambogic acid interacted with an allosteric site on the CYP2B6 surface. Natural product constituents may inhibit CYP2B6 and methadone metabolism at clinically relevant concentrations.

Intravenous methadone in the management of acute postoperative pain in a chronic cancer pain patient: A case report and review of the literature

Key Clinical Message

The current landscape of literature highlights that there is insufficient well-powered and robust evidence to support the integration of intravenous methadone into current guidelines and frameworks in supporting the pain management of cancer patient with complex pain syndromes. However, there is preliminary evidence, both from the literature as well as this case study that highlights intravenous methadone may be efficaciously and safety used for the management of postoperative pain in cancer patients with chronic pain undergoing operative management. Further research is required to fully elucidate key considerations of integrating this medication into clinical practice including consideration into dosing, opioid conversion, tolerance, and safety.

Abstract

Methadone is a broad-spectrum analgesic with long duration of effect. Its multimodal mechanism of action, such as through effects on mu-opioid receptor and presynaptic N-methyl-D-aspartate receptors, has led to its current use in the management of opioid dependence in the community and in palliative care. These properties however make methadone appealing in the management of postoperative pain, particularly for patients with complex analgesic requirements. We report on an interesting case whereby intravenous methadone was effectively used for postoperative analgesia in a 56-year-old female with complex chronic pain secondary to a mucinous pelvic neoplasm of unclear primary who underwent palliative resection. Further, we review the literature surrounding usage of methadone in this setting to understand current challenges and barriers to implementation of methadone as an analgesia option for chronic pain patients following surgery. To do this, a case report and literature review was conducted in accordance to the CARE case report guidelines. The patient provided written consent for the de-identification and use of their medical information and data for the generation and publication of this case report. Our case report and literature review demonstrate there remains significant heterogeneity, unfamiliarity, and scarce use of intravenous methadone in the perioperative and postoperative space in the management of patients with complex pain regimens such as chronic cancer pain patients. Despite this, our case report and literature review highlight as a broad analgesic, intravenous methadone warrants consideration following more rigorous research and development of safe use guidelines into its use for this purpose.

Intraoperative Methadone in Next-day Discharge Outpatient Surgery: A Randomized, Double-blinded, Dose-finding Pilot Study

BACKGROUND

Contemporary perioperative practice seeks to use less intraoperative opioid, diminish postoperative pain and opioid use, and enable less postdischarge opioid prescribing. For inpatient surgery, anesthesia with intraoperative methadone, compared with short-duration opioids, results in less pain, less postoperative opioid use, and greater patient satisfaction. This pilot investigation aimed to determine single-dose intraoperative methadone feasibility for next-day discharge outpatient surgery, determine an optimally analgesic and well-tolerated dose, and explore whether methadone would result in less postoperative opioid use compared with conventional short-duration opioids.

METHODS

This double-blind, randomized, dose-escalation feasibility and pilot study in next-day discharge surgery compared intraoperative single-dose IV methadone (0.1 then 0.2, 0.25 and 0.3 mg/kg ideal body weight) versus as-needed short-duration opioid (fentanyl, hydromorphone) controls. Perioperative opioid use, pain, and side effects were assessed before discharge. Patients recorded pain, opioid use, and side effects for 30 days postoperatively using take-home diaries. Primary clinical outcome was in-hospital (intraoperative and postoperative) opioid use. Secondary outcomes were 30-day opioid consumption, pain, opioid side effects, and leftover opioid counts.

RESULTS

Median (interquartile range) intraoperative methadone doses were 6 (5 to 7), 11 (10 to 12), 14 (13 to 16), and 18 (15 to 19) mg in 0.1, 0.2, 0.25, and 0.3 mg/kg ideal body weight groups, respectively. Anesthesia with single-dose methadone and propofol or volatile anesthetic was effective. Total in-hospital opioid use (IV milligram morphine equivalents [MME]) was 25 (20 to 37), 20 (13 to 30), 27 (18 to 32), and 25 (20 to 36) mg, respectively, in patients receiving 0.1, 0.2, 0.25 and 0.3 mg/kg methadone, compared to 46 (33 to 59) mg in short-duration opioid controls. Opioid-related side effects were not numerically different. Home pain and opioid use were numerically lower in patients receiving methadone.

CONCLUSIONS

The most effective and well-tolerated single intraoperative induction dose of methadone for next-day discharge surgery was 0.25 mg/kg ideal body weight (median, 14 mg). Single-dose intraoperative methadone was analgesic and opioid-sparing in next-day discharge outpatient surgery.

EDITOR’S PERSPECTIVE

Switching to Intravenous Methadone in Advanced Cancer Patients: A Retrospective Analysis

CONTEXT

Information about opioid switching to intravenous methadone is lacking.

OBJECTIVES

The aim of this study was to assess the outcome of opioid switching to intravenous methadone (IV-ME) in patients admitted to an acute supportive/palliative care unit (ASPCU). The secondary outcome was to assess the conversion ratio from IV-ME to oral methadone at time of hospital discharge.

METHODS

We retrieved from the pharmacy registry the list of patients who were prescribed IV-ME during their ASPCU admission for a period of 47 months. Poor analgesia with previous opioids and/or adverse effects were the main indications for opioid switching. IV-ME was titrated until acceptable analgesia was achieved. The effective dose was multiplied by three to establish the intravenous daily dose, given as a continuous infusion. Doses were then changed according to the clinical needs. Once the patient was stabilized, IV-ME dose was converted to oral methadone, by using an initial ratio of 1:1.2. Further dose changes were made according to clinical needs until stabilization, before patients' discharge. Information about patients' characteristics, pain scores on the Edmonton Symptom Assessment Scale (ESAS), Memorial Delirium Assessment Scale (MDAS), Cut-down, Annoyed, Guilty, Eye-opener (CAGE) questionnaire, previous opioids and their doses, expressed as oral morphine equivalents (OME), were recorded. The effective bolus of IV-ME, initial daily infusion rate, and oral methadone doses were assessed, and conversion ratios calculated.

RESULTS

Forty-one patients were taken into consideration for the study. The mean effective bolus of IV-ME titrated for achieving acceptable analgesia was 9 mg (range 5-15 mg). The mean daily continuous infusion rate of IV-ME was 27.6 mg/day (SD 21). The mean daily dose of oral methadone at time of discharge was 46.8 mg/day (SD 43). Discharge occurred within a median of seven days (range 6-9) after admission. Previous opioid (OME)/IV-ME, oral-IV-ME, and previous opioid (OME)/oral methadone were 6.25, 1.7, and 3.7, respectively.

CONCLUSION

IV-ME dose titration followed by intravenous infusion allowed a rapid pain control in few minutes in patients with severe pain intensity, not responsive to previous opioids. Conversion to oral route was successful and facilitated home discharge. Further studies should be performed to confirm these preliminary results.

The Use of Parenteral Opioids in Cancer Pain Management

Opioids should be offered to patients with moderate-to-severe pain related to cancer or active cancer treatment unless contraindicated. Although oral administration of opioids is generally preferable, a parenteral route may be advisable and mandatory in some clinical circumstances. Parenteral administration of opioids may accelerate the achievement of analgesia. The intravenous route fits the need of rapid achievement of analgesia in patients poorly responsive to other opioids and provides a fast analgesia in patients with breakthrough pain, that has a specific temporal pattern requiring a rapid analgesic effect. When the oral route is unavailable for the presence of nausea, vomiting, or dysphagia. the parenteral route is one of the principal options. Opioids have different pharmacokinetic and pharmacodynamic characteristics and should be chosen according to the individual needs. Thus, the knowledge and experience with these routes of administration are mandatory for anesthesiologists committed to cancer pain management.

Comparison of oral versus intravenous methadone on postoperative pain and opioid use after adult spinal deformity surgery: A retrospective, non-inferiority analysis

OBJECTIVE

To compare efficacy of oral versus intravenous (IV) methadone on postoperative pain and opioid requirements after spine surgery.

METHODS

This was a retrospective, single-academic center cohort study evaluating 1010 patients who underwent >3 level spine surgery from January 2017 to May 2020 and received a one-time dose of oral or intravenous methadone prior to surgery. The primary outcome measured was postoperative opioid use in oral morphine equivalents (ME) and verbal response scale (VRS) pain scores up to postoperative day (POD) three. Secondary outcomes were time to first bowel movement and adverse effects (reintubation, myocardial infarction, and QTc prolongation) up to POD 3.

RESULTS

A total of 687 patients received oral and 317 received IV methadone, six patients were excluded. The IV group received a significantly greater methadone morphine equivalent (ME) dose preoperatively (112.4 ± 83.0 mg ME versus 59.3 ± 60.9 mg ME, p < 0.001) and greater total (methadone and non-methadone) opioid dose (119.1 ± 81.4 mg ME versus 63.9 ± 62.5 mg ME, p < 0.001), intraoperatively. Although pain scores for the oral group were non-inferior to the IV group for all postoperative days (POD), non-inferiority for postoperative opioid requirements was demonstrated only on POD 3. Based on the joint hypothesis for the co-primary outcomes, oral methadone was non-inferior to IV methadone on POD 3 only. No differences in secondary outcomes, including QTc prolongation and arrhythmias, were noted between the groups.

CONCLUSIONS

Oral methadone is a feasible alternative to IV methadone for patients undergoing spine surgery regarding both pain scores and postoperative opioid consumption.

Intravenous Methadone for Perioperative and Chronic Cancer Pain: A Review of the Literature

Intravenous methadone may be useful in acute and chronic pain management compared with other opioids because of its pharmacokinetic and pharmacodynamic characteristics, including the long duration of effect and ability to modulate both pain stimuli propagation and analgesic descending pathways. However, methadone is underused in pain medicine because of several misperceptions. A review of studies was performed to assess data regarding the use of methadone in perioperative pain and chronic cancer pain. The majority of studies have shown that intravenous methadone produces an effective postoperative analgesia and lowers opioid consumption in the postoperative period, without more adverse effects in comparison with other opioid analgesics, and has an interesting potential to prevent persistent postoperative pain. A minority of studies investigated the use of intravenous methadone for cancer pain management. These studies were mostly case series that showed promising activities of intravenous methadone for difficult pain conditions. There is sufficient evidence suggesting that intravenous methadone is effective in perioperative pain, while more studies are needed in patients with cancer pain.

Pro-Con Debate: Role of Methadone in Enhanced Recovery After Surgery Protocols-Superior Analgesic or Harmful Drug?

Enhanced recovery after surgery (ERAS) protocols are standardized and designed to provide superior analgesia, reduce opioid consumption, improve patient recovery, and reduce hospital length of stay. Yet, moderate-to-severe postsurgical pain continues to afflict over 40% of patients and remains a major priority for anesthesia research. Methadone administration in the perioperative setting may reduce postoperative pain scores and have opioid-sparing effects, which may be beneficial for enhanced recovery. Methadone possesses a multimodal profile consisting of µ-opioid agonism, N-methyl-d-aspartate (NMDA) receptor antagonism, and reuptake inhibition of serotonin and norepinephrine. Furthermore, it may attenuate the development of chronic postsurgical pain. However, caution is advised with perioperative use of methadone in specific high-risk patient populations and surgical settings. Methadone's wide pharmacokinetic variability, opioid-related adverse effects, and potential negative impact on cost-effectiveness may also limit its use in the perioperative setting. In this PRO-CON commentary article, the authors debate whether methadone should be incorporated in ERAS protocols to provide superior analgesia with no increased risks.

Morphine and Hydromorphone Effects, Side Effects, and Variability: A Crossover Study in Human Volunteers

BACKGROUND

Balancing between opioid analgesia and respiratory depression continues to challenge clinicians in perioperative, emergency department, and other acute care settings. Morphine and hydromorphone are postoperative analgesic standards. Nevertheless, their comparative effects and side effects, timing, and respective variabilities remain poorly understood. This study tested the hypothesis that IV morphine and hydromorphone differ in onset, magnitude, duration, and variability of analgesic and ventilatory effects.

METHODS

The authors conducted a randomized crossover study in healthy volunteers. Forty-two subjects received a 2-h IV infusion of hydromorphone (0.05 mg/kg) or morphine (0.2 mg/kg) 1 to 2 weeks apart. The authors measured arterial opioid concentrations, analgesia in response to heat pain (maximally tolerated temperature, and verbal analog pain scores at discrete preset temperatures to determine half-maximum temperature effect), dark-adapted pupil diameter and miosis, end-expired carbon dioxide, and respiratory rate for 12 h after dosing.

RESULTS

For morphine and hydromorphone, respectively, maximum miosis was less (3.9 [3.4 to 4.2] vs. 4.6 mm [4.0 to 5.0], P < 0.001; median and 25 to 75% quantiles) and occurred later (3.1 ± 0.9 vs. 2.3 ± 0.7 h after infusion start, P < 0.001; mean ± SD); maximum tolerated temperature was less (49 ± 2 vs. 50 ± 2°C, P < 0.001); verbal pain scores at end-infusion at the most informative stimulus (48.2°C) were 82 ± 4 and 59 ± 3 (P < 0.001); maximum end-expired CO2 was 47 (45 to 50) and 48 mmHg (46 to 51; P = 0.007) and occurred later (5.5 ± 2.8 vs. 3.0 ± 1.5 h after infusion start, P < 0.001); and respiratory nadir was 9 ± 1 and 11 ± 2 breaths/min (P < 0.001), and occurred at similar times. The area under the temperature tolerance-time curve was less for morphine (1.8 [0.0 to 4.4]) than hydromorphone (5.4°C-h [1.6 to 12.1] P < 0.001). Interindividual variability in clinical effects did not differ between opioids.

CONCLUSIONS

For morphine compared to hydromorphone, analgesia and analgesia relative to respiratory depression were less, onset of miosis and respiratory depression was later, and duration of respiratory depression was longer. For each opioid, timing of the various clinical effects was not coincident. Results may enable more rational opioid selection, and suggest hydromorphone may have a better clinical profile.

EDITOR’S PERSPECTIVE

Retrospective Study of the Safety and Efficacy of Intraoperative Methadone for Pain Management in Patients Undergoing Elective Intracranial Surgery

BACKGROUND

Patients undergoing intracranial surgery experience significant perioperative pain and are typically treated with short-acting opioids. Methadone, with its prolonged half-life and multimodal central nervous system effects, presents a promising option for managing postcraniotomy pain. Despite its proven efficacy in other types of surgeries, the use of methadone in patients undergoing craniotomy has not yet been explored.

METHODS

A retrospective chart review was conducted for 60 adult patients ranging in age from 18 to 81 years who received methadone during intracranial surgeries. The primary outcome of interest was the total opioid consumption in oral morphine milligram equivalents (MMEs) and patient-reported pain scores within 24 hours and up to 72 hours postoperatively.

RESULTS

The methadone dosage varied from 5 to 20 mg. In the infratentorial group, the median total MME on postoperative day 1, 2, and 3 was 30.5, 17, and 0.8, respectively, with mean pain scores of 3.56, 3.91, and 2.71. In the supratentorial group, the median total MME on postoperative day 1, 2, and 3 was 17.85, 15.4, and 1.2, with mean pain scores of 2.31, 1.68, and 2.21, respectively. Patients who were chronic opioid users had significantly higher pain scores and average opioid use (P < 0.05). None of the patients required administration of naloxone or airway interventions. Comparison with the historical control showed that our study patients had lower pain scores and MME.

CONCLUSIONS

The single intraoperative dose of methadone is well tolerated by adult patients undergoing various types of intracranial surgeries, with minimal side effects, including elderly patients aged 65 years or older.

Short-acting versus long-acting opioids for pediatric postoperative pain management

INTRODUCTION

Opioids are potent analgesics commonly used to manage children's moderate to severe perioperative pain in children. A wide range of short and long-acting opioids are used to treat surgical pain and will be reviewed in this article.

AREAS COVERED

Both short- and long-acting opioids contain unique therapeutic benefits and adverse effects; however, due to the side effect profile and safety concerns, lack of familiarity, and evidence with long-acting opioids to treat surgical pain, shorter-acting opioids have traditionally been used in children. Almost all opioids work by binding to the mu receptor. Methadone, a long-acting opioid, is an exception because it also has beneficial N-methyl-D-aspartate antagonist properties. Clinically methadone's properties could translate to improved analgesic outcomes, reduced risk of adverse events, less risk for acute hyperalgesia, tolerance and abuse potential, faster recovery, and reduced risk for chronic persistent surgical pain. This review article summarizes and compares the evidence of commonly used short and long-acting opioids for perioperative pain control in the pediatric population.

EXPERT OPINION

Individualized methadone therapy using pharmacogenomics has the potential to transform opioid use in pain management by improving patient safety and analgesic outcomes, thereby addressing the gaps in current standardized ERAS protocols.

Effect of deuteration on the single dose pharmacokinetic properties and postoperative analgesic activity of methadone

Although methadone is effective in the management of acute pain, the complexity of its absorption-distribution-metabolism-excretion profile limits its use as an opioid of choice for perioperative analgesia. Because deuteration is known to improve the pharmacokinetic, pharmacodynamic and toxicological properties of some drugs, here we characterized the single dose pharmacokinetic properties and post-operative analgesic efficacy of d9-methadone. The pharmacokinetic profiles of d9-methadone and methadone administered intravenously to CD-1 male mice revealed that deuteration leads to a 5.7- and 4.4-fold increase in the area under the time-concentration curve and maximum concentration in plasma, respectively, as well as reduction in clearance (0.9 ± 0.3 L/h/kg vs 4.7 ± 0.8 L/h/kg). The lower brain-to-plasma ratio of d9-methadone compared to that of methadone (0.35 ± 0.12 vs 2.05 ± 0.62) suggested that deuteration decreases the transfer of the drug across the blood-brain barrier. The estimated LD50 value for a single intravenous dose of d9-methadone was 2.1-fold higher than that for methadone. Moreover, d9-methadone outperformed methadone in the efficacy against postoperative pain by primarily activating peripheral opioid receptors. Collectively, these data suggest that the replacement of three hydrogen atoms in three methyl groups of methadone altered its pharmacokinetic properties, improved safety, and enhanced its analgesic efficacy.

Methadone pharmacogenetics in vitro and in vivo: Metabolism by CYP2B6 polymorphic variants and genetic variability in paediatric disposition

AIMS

Methadone metabolism and clearance are determined principally by polymorphic cytochrome P4502B6 (CYP2B6). Some CYP2B6 allelic variants affect methadone metabolism in vitro and disposition in vivo. We assessed methadone metabolism by CYP2B6 minor variants in vitro. We also assessed the influence of CYP2B6 variants, and P450 oxidoreductase (POR) and CYP2C19 variants, on methadone clearance in surgical patients in vivo.

METHODS

CYP2B6 and P450 oxidoreductase variants were coexpressed with cytochrome b5 . The metabolism of methadone racemate and enantiomers was measured at therapeutic concentrations and intrinsic clearances were determined. Adolescents receiving methadone for surgery were genotyped for CYP2B6, CYP2C19 and POR, and methadone clearance and metabolite formation clearance were determined.

RESULTS

In vitro, CYP2B6.4 was more active than wild-type CYP2B6.1. CYPs 2B6.5, 2B6.6, 2B6.7, 2B6.9, 2B6.17, 2B6.19 and 2B6.26 were less active. CYPs 2B6.16 and 2B6.18 were inactive. CYP2B6.1 expressed with POR variants POR.28, POR.5 and P228L had lower rates of methadone metabolism than wild-type reductase. In vivo, methadone clinical clearance decreased linearly with the number of CYP2B6 slow metabolizer alleles, but was not different in CYP2C19 slow or rapid metabolizer phenotypes, or in carriers of the POR*28 allele.

CONCLUSIONS

Several CYP2B6 and POR variants were slow metabolizers of methadone in vitro. Polymorphisms in CYP2B6, but not CYP2C19 or P450 reductase, affected methadone clearance in vivo. CYP2B6 polymorphisms 516G>T and 983T>C code for canonical loss of function variants and should be assessed when considering genetic influences on clinical methadone disposition. These complementary translational in vitro and in vivo results inform on pharmacogenetic variability affecting methadone disposition in patients.

Multimodal Approach to Vertebral Body Tethering With Erector Spinae Plane Blocks and Cryoablation

Multimodal analgesia that combines around-the-clock medications and regional techniques can be especially effective for postoperative pain control. We describe a pediatric patient who underwent vertebral body tethering via an open thoracolumbar approach to treat juvenile idiopathic scoliosis. Erector spinae plane blocks (ESPBs), cryoablation to the intercostal nerves, and multimodal medications helped control our patient's pain well enough for her to be discharged home on postoperative day 2. To the best of our knowledge, this is the first report of this combination of regional techniques used for vertebral body tethering (VBT).

Intraoperative Methadone and Short Stay Spine Surgery: Possible Barriers to Implementation and Future Opportunities

The frequency of shorter stay spine surgery is increasing. Acute pain is a common barrier to discharge following spine surgery. Long-acting opioid medications like methadone have the potential to provide sustained analgesia when given intraoperatively. Methadone has been effectively used in complex spine surgery, cardiac surgery, and more recently applied to ambulatory procedures. In this article, we summarize the pertinent available literature on the use of intraoperative methadone for spine surgery as well as the recent data on intraoperative methadone for ambulatory surgery. The aim of this perspectives article is to describe the potential opportunities for applying intraoperative methadone to shorter stay spine surgery as well as barriers to more widespread use. While there are currently no trials that have specifically studied methadone for shorter stay spine surgery specifically to date, it is a promising area for future research.

Management of Postoperative Pain in Patients Following Spine Surgery: A Narrative Review

Perioperative pain management is a unique challenge in patients undergoing spine surgery due to the increased incidence of both pre-existing chronic pain conditions and chronic postsurgical pain. Peri-operative planning and counseling in spine surgery should involve an interdisciplinary approach that includes consideration of patient-level risk factors, as well as pharmacologic and non-pharmacologic pain management techniques. Consideration of psychological factors and patient focused education as an adjunct to these measures is paramount in developing a personalized perioperative pain management plan. Understanding the currently available body of knowledge surrounding perioperative opioid management, management of opioid use disorder, regional/neuraxial anesthetic techniques, ketamine/lidocaine infusions, non-opioid oral analgesics, and behavioral interventions can be useful in developing a comprehensive, multi-modal treatment plan among patients undergoing spine surgery. Although many of these techniques have proved efficacious in the immediate postoperative period, long-term follow-up is needed to define the impact of such approaches on persistent pain and opioid use. Future techniques involving the use of precision medicine may help identify phenotypic and physiologic characteristics that can identify patients that are most at risk of developing persistent postoperative pain after spine surgery.

Rediscovery of Methadone to Improve Outcomes in Pain Management

Clinically, methadone is most known for its use in the treatment of opioid maintenance therapy. However, methadone's pharmacological profile makes it an excellent analgesic that can enhance acute and chronic pain management. It is a potent μ-receptor agonist with a longer elimination half-life than most clinically used opioids. In addition, methadone inhibits serotonin and norepinephrine uptake, and it is an N-methyl-D-aspartate antagonist. These distinct analgesic pathways mediate hyperalgesic, allodynic, and neuropathic pain. Its unique analgesic properties provide several essential benefits in perioperative use, neuropathic pain, cancer, and noncancer pain. Despite these proven clinical utilities, methadone has not been used widely to treat acute and chronic pain in opioid naïve patients. This article describes the unique pharmacology of methadone and provides emerging evidence to support its application in acute and chronic pain management. Pain management options and guidelines for surgical patients on methadone are discussed as well.

Opioid-Sparing Perioperative Analgesia Within Enhanced Recovery Programs

Opioid-based analgesia in the perioperative period can provide excellent pain control, but this approach exposes the patient to avoidable side effects and possible harm. Optimal analgesia, an approach that targets the fastest functional recovery with adequate pain control while minimizing side effects, can be achieved with opioid minimization. Many different options for nonopioid multimodal analgesia exist and have been shown to be efficacious, with certain modalities being more beneficial for specific surgeries. This review will present the evidence and practical tips for these management strategies.

Opioids and Public Health: The Prescription Opioid Ecosystem and Need for Improved Management

While U.S. opioid prescribing has decreased 38% in the past decade, opioid deaths have increased 300%. This opioid paradox is poorly recognized. Current approaches to opioid management are not working, and new approaches are needed. This article reviews the outcomes and shortcomings of recent U.S. opioid policies and strategies that focus primarily or exclusively on reducing or eliminating opioid prescribing. It introduces concepts of a prescription opioid ecosystem and opioid pool, and it discusses how the pool can be influenced by supply-side, demand-side, and opioid returns factors. It illuminates pressing policy needs for an opioid ecosystem that enables proper opioid stewardship, identifies associated responsibilities, and emphasizes the necessity of making opioid returns as easy and common as opioid prescribing, in order to minimize the size of the opioid pool available for potential diversion, misuse, overdose, and death. Approaches are applicable to opioid prescribing in general, and to opioid prescribing after surgery.

Impact of intraoperative methadone use on postoperative opioid requirements after cardiac surgery

DISCLAIMER

In an effort to expedite the publication of articles, AJHP is posting manuscripts online as soon as possible after acceptance. Accepted manuscripts have been peer-reviewed and copyedited, but are posted online before technical formatting and author proofing. These manuscripts are not the final version of record and will be replaced with the final article (formatted per AJHP style and proofed by the authors) at a later time.

PURPOSE

Inadequate pain control after cardiac surgery increases postoperative morbidity. Increasing evidence suggests that perioperative intravenous (IV) methadone results in improved analgesia. This study evaluated the effect of intraoperative IV methadone on postoperative opioid requirements and surgical recovery.

METHODS

A retrospective review of patients undergoing coronary artery bypass graft (CABG), valvular surgery or both between April 2017 and August 2018 was conducted. Patients were separated into a usual care cohort of those who received short-acting opioids (ie, IV fentanyl, hydromorphone, or morphine) alone or a methadone cohort of those who received IV methadone plus short-acting opioids. Opioid requirements were assessed within the first 24 hours of surgery (postoperative day [POD] 0) and 25 to 48 hours after surgery (POD 1) as oral morphine milligram equivalents (MME). Postoperative pain scores, adjunctive analgesia, time to extubation, use of noninvasive respiratory support (continuous positive airway pressure [CPAP] or bilevel positive airway pressure [BiPAP]), and intensive care unit (ICU) and hospital length of stay (LOS) were also evaluated.

RESULTS

A total of 117 patients were evaluated (methadone cohort, n = 52; usual care cohort, n = 65). Median cumulative intraoperative opioid consumption was less in the methadone cohort (150 MME vs 314.1 MME; P < 0.0001). The methadone cohort required 44% fewer MME than the usual care cohort on POD 0 (median MME, 15.8 vs 36; P = 0.025), with low and not significantly different opioid use in both cohorts on POD 1 (15.5 MME vs 7.5 MME; P = 0.47). Weight-based methadone dosing ranged from 0.1 to 0.4 mg/kg (mean, 0.22 mg/kg). There were no significant differences in pain scores, time to extubation, use of CPAP or BiPAP, or ICU and hospital LOS.

CONCLUSION

Intraoperative IV methadone in cardiac surgery patients was safe and significantly reduced intraoperative and postoperative opioid requirements on POD 0.

Intraoperative Methadone Reduces Postoperative Opioid Requirements in Nuss Procedure for Pectus Excavatum

INTRODUCTION

Surgical correction of pectus excavatum by Nuss procedure, commonly referred to as minimally invasive repair of pectus excavatum (MIRPE), often results in significant postoperative pain. This study investigated whether adding intraoperative methadone would reduce the postoperative opioid requirement during admission for patients undergoing MIRPE.

METHODS

A retrospective cohort chart review was conducted for 40 MIRPE patients between 2018 and 2020. Patients were stratified into 2 groups: those who received multimodal anesthesia (MM, n = 20) and those who received multimodal anesthesia with the addition of intraoperative methadone (MM + M, n = 20). Data collected included total opioid consumption during hospital stay (morphine milligram equivalents [MMEs]), hospital length of stay (LOS), pain scores, time to ambulation, and time to tolerating solid food.

RESULTS

Addition of intraoperative methadone for patients undergoing MIRPE significantly reduced postoperative opioid requirements (MME/kg) during admission (P = .007). On average, patients in the MM group received 1.61 ± .55 MME/kg while patients in the MM + M group received 1.16 ± .44 MME/kg. Hospital opioid (non-methadone) total was also significantly reduced between the MM (1.87 ± .54) and MM + M group (1.37 ± .46), P = .003. There was no significant difference in hospital opioid total MME/kg administered between the groups. There were no significant differences observed in hospital LOS, pain scores, time to ambulation, or time to toleration of solid food.

DISCUSSION

Incorporating intraoperative methadone for patients undergoing MIRPE reduced postoperative opioid requirements and hospital opioid (non-methadone) totals without a significant change in pain scores. Patients undergoing the Nuss procedure may benefit from the administration of intraoperative methadone.

Intraoperative Methadone Use in Cardiac Surgery: A Systematic Review

OBJECTIVE

To investigate the effects of intraoperative methadone to standard of care opioids such as fentanyl and morphine on pain scores, opioid consumption, and adverse effects in adults undergoing cardiothoracic surgery.

METHODS

The literature was reviewed on PubMed, Embase, Cochrane Library, and Google Scholar, followed by a manual search using reference lists of the identified articles. Search terms included a combination of intraoperative methadone, methadone, and cardiac surgery. Our review includes four studies published between 2011 and 2020. Quality assessment of the studies was performed.

RESULTS

The initial search identified 715 articles with 461 duplicates removed, and 236 eliminated based on inclusion and exclusion criteria. Eighteen articles underwent full-text review. Four studies evaluating a total of 435 patients with various cardiothoracic procedures were included in this review. We found that intraoperative methadone decreases acute postoperative pain and reduces postoperative opioid consumption in the first 24 postoperative hours in patients who received 0.1-0.3 mg/kg intraoperative methadone in comparison to morphine and fentanyl. No difference was found in adverse effects between the groups. Quality assessment of the studies showed a low risk of bias in three of the randomized controlled trials and a high risk of bias in the retrospective review because of the baseline confounding bias in the study design.

CONCLUSIONS

Intraoperative methadone use reduces acute postoperative pain and lowers opioid consumption in comparison to morphine and fentanyl. Initial results suggest that methadone may be an equivalent opioid to be administered during cardiothoracic procedures to reduce acute post-surgical pain, though further research is warranted.

Postoperative pain: a review of emerging therapeutic options

INTRODUCTION

Postoperative pain is often managed by opioid medications, even though they carry a risk of adverse effects such as vomiting, constipation, sedation, respiratory depression and physical dependence. Furthermore, opioid use in the healthcare setting has likely contributed to the epidemic. However, the mismanagement of postoperative pain can result in delayed recovery time, impaired physical function, increased risk of morbidity and mortality, chronic pain, and higher healthcare costs.

AREAS COVERED

This review explores emerging therapeutic options and strategies in the management of acute postoperative pain and focuses on opioid-sparing, multimodal analgesia. This includes regional anesthetic techniques, non opioid pharmacotherapy, novel opioids and non-pharmacologic therapy. We have also discussed examples of novel analgesics and formulations which have potential benefits in reducing postoperative pain and opioid use after surgery.

EXPERT OPINION

The development of novel regional anesthesia techniques allows for opioid minimization in increasing number of surgical procedures. This synergizes with the availability of novel non-opioid analgesic adjucts. In addition, several novel opioid drugs have been developed which may be pathway selective and associated with less adverse effect than conventional opioids.

A Novel Perioperative Multidose Methadone-Based Multimodal Analgesic Strategy in Children Achieved Safe and Low Analgesic Blood Methadone Levels Enabling Opioid-Sparing Sustained Analgesia With Minimal Adverse Effects

BACKGROUND

Intraoperative methadone, a long-acting opioid, is increasingly used for postoperative analgesia, although the optimal methadone dosing strategy in children is still unknown. The use of a single large dose of intraoperative methadone is controversial due to inconsistent reductions in total opioid use in children and adverse effects. We recently demonstrated that small, repeated doses of methadone intraoperatively and postoperatively provided sustained analgesia and reduced opioid use without respiratory depression. The aim of this study was to characterize pharmacokinetics, efficacy, and safety of a multiple small-dose methadone strategy.

METHODS

Adolescents undergoing posterior spinal fusion (PSF) for idiopathic scoliosis or pectus excavatum (PE) repair received methadone intraoperatively (0.1 mg/kg, maximum 5 mg) and postoperatively every 12 hours for 3-5 doses in a multimodal analgesic protocol. Blood samples were collected up to 72 hours postoperatively and analyzed for R-methadone and S-methadone, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidene (EDDP) metabolites, and alpha-1 acid glycoprotein (AAG), the primary methadone-binding protein. Peak and trough concentrations of enantiomers, total methadone, and AAG levels were correlated with clinical outcomes including pain scores, postoperative nausea and vomiting (PONV), respiratory depression, and QT interval prolongation.

RESULTS

The study population included 38 children (10.8-17.9 years): 25 PSF and 13 PE patients. Median total methadone peak plasma concentration was 24.7 (interquartile range [IQR], 19.2-40.8) ng/mL and the median trough was 4.09 (IQR, 2.74-6.4) ng/mL. AAG concentration almost doubled at 48 hours after surgery (median = 193.9, IQR = 86.3-279.5 µg/mL) from intraoperative levels (median = 87.4, IQR = 70.6-115.8 µg/mL; P < .001), and change of AAG from intraoperative period to 48 hours postoperatively correlated with R-EDDP (P < .001) levels, S-EDDP (P < .001) levels, and pain scores (P = .008). Median opioid usage was minimal, 0.66 (IQR, 0.59-0.75) mg/kg morphine equivalents/d. No respiratory depression (95% Wilson binomial confidence, 0-0.09) or clinically significant QT prolongation (median = 9, IQR = -10 to 28 milliseconds) occurred. PONV occurred in 12 patients and was correlated with morphine equivalent dose (P = .005).

CONCLUSIONS

Novel multiple small perioperative methadone doses resulted in safe and lower blood methadone levels, <100 ng/mL, a threshold previously associated with respiratory depression. This methadone dosing in a multimodal regimen resulted in lower blood methadone analgesia concentrations than the historically described minimum analgesic concentrations of methadone from an era before multimodal postoperative analgesia without postoperative respiratory depression and prolonged corrected QT (QTc). Larger studies are needed to further study the safety and efficacy of this methadone dosing strategy.

CYP2B6 Functional Variability in Drug Metabolism and Exposure Across Populations-Implication for Drug Safety, Dosing, and Individualized Therapy

Adverse drug reactions (ADRs) are one of the major causes of morbidity and mortality worldwide. It is well-known that individual genetic make-up is one of the causative factors of ADRs. Approximately 14 million single nucleotide polymorphisms (SNPs) are distributed throughout the entire human genome and every patient has a distinct genetic make-up which influences their response to drug therapy. Cytochrome P450 2B6 (CYP2B6) is involved in the metabolism of antiretroviral, antimalarial, anticancer, and antidepressant drugs. These drug classes are commonly in use worldwide and face specific population variability in side effects and dosing. Parts of this variability may be caused by single nucleotide polymorphisms (SNPs) in the CYP2B6 gene that are associated with altered protein expression and catalytic function. Population variability in the CYP2B6 gene leads to changes in drug metabolism which may result in adverse drug reactions or therapeutic failure. So far more than 30 non-synonymous variants in CYP2B6 gene have been reported. The occurrence of these variants show intra and interpopulation variability, thus affecting drug efficacy at individual and population level. Differences in disease conditions and affordability of drug therapy further explain why some individuals or populations are more exposed to CYP2B6 pharmacogenomics associated ADRs than others. Variabilities in drug efficacy associated with the pharmacogenomics of CYP2B6 have been reported in various populations. The aim of this review is to highlight reports from various ethnicities that emphasize on the relationship between CYP2B6 pharmacogenomics variability and the occurrence of adverse drug reactions. In vitro and in vivo studies evaluating the catalytic activity of CYP2B6 variants using various substrates will also be discussed. While implementation of pharmacogenomic testing for personalized drug therapy has made big progress, less data on pharmacogenetics of drug safety has been gained in terms of CYP2B6 substrates. Therefore, reviewing the existing evidence on population variability in CYP2B6 and ADR risk profiles suggests that, in addition to other factors, the knowledge on pharmacogenomics of CYP2B6 in patient treatment may be useful for the development of personalized medicine with regards to genotype-based prescription.

Perioperative Methadone and Ketamine for Postoperative Pain Control in Spinal Surgical Patients: A Randomized, Double-blind, Placebo-controlled Trial

BACKGROUND

Despite application of multimodal pain management strategies, patients undergoing spinal fusion surgery frequently report severe postoperative pain. Methadone and ketamine, which are N-methyl-d-aspartate receptor antagonists, have been documented to facilitate postoperative pain control. This study therefore tested the primary hypothesis that patients recovering from spinal fusion surgery who are given ketamine and methadone use less hydromorphone on the first postoperative day than those give methadone alone.

METHODS

In this randomized, double-blind, placebo-controlled trial, 130 spinal surgery patients were randomized to receive either methadone at 0.2 mg/kg (ideal body weight) intraoperatively and a 5% dextrose in water infusion for 48 h postoperatively (methadone group) or 0.2 mg/kg methadone intraoperatively and a ketamine infusion (0.3 mg · kg-1 · h-1 infusion [no bolus] intraoperatively and then 0.1 mg · kg-1 · h-1 for next 48 h [both medications dosed at ideal body weight]; methadone/ketamine group). Anesthetic care was standardized in all patients. Intravenous hydromorphone use on postoperative day 1 was the primary outcome. Pain scores, intravenous and oral opioid requirements, and patient satisfaction with pain management were assessed for the first 3 postoperative days.

RESULTS

Median (interquartile range) intravenous hydromorphone requirements were lower in the methadone/ketamine group on postoperative day 1 (2.0 [1.0 to 3.0] vs. 4.6 [3.2 to 6.6] mg in the methadone group, median difference [95% CI] 2.5 [1.8 to 3.3] mg; P < 0.0001) and postoperative day 2. In addition, fewer oral opioid tablets were needed in the methadone/ketamine group on postoperative day 1 (2 [0 to 3] vs. 4 [0 to 8] in the methadone group; P = 0.001) and postoperative day 3. Pain scores at rest, with coughing, and with movement were lower in the methadone/ketamine group at 23 of the 24 assessment times. Patient-reported satisfaction scores were high in both study groups.

CONCLUSIONS

Postoperative analgesia was enhanced by the combination of methadone and ketamine, which act on both N-methyl-d-aspartate and μ-opioid receptors. The combination could be considered in patients having spine surgery.

EDITOR’S PERSPECTIVE

Effect of intraoperative methadone vs other opioids on postoperative outcomes: a meta-analysis of randomized controlled studies

ABSTRACT

Recent randomized controlled trials comparing the efficacy between intraoperative methadone and other opioids on postoperative outcomes have been limited by their small sample sizes and conflicting results. We performed a meta-analysis on randomized controlled trials which investigated outcomes between methadone and an opioid control group. Primary outcome data included postoperative opioid consumption, number of patients who received postoperative opioids, time to first analgesic, and pain scores. Secondary outcomes included time to extubation and incidence of nausea, vomiting, and respiratory depression. Statistical analysis was performed using RevMan. A P < 0.05 was considered statistically significant. Nine studies comprising 632 patients were included. There was no statistically significant reduction in opioid consumption postoperatively between the groups. Forty-seven percentage of patients in the methadone group received a dose of opioid postoperatively compared with 55% in the other opioids control group, which was not statistically significant. (P = 0.25) There was no difference in average time to receiving first postoperative analgesic among the groups. Pain scores within 24 hours were significantly lower in the methadone group when compared with other opioids (8 studies, n = 622, -0.49 [-0.74, -0.23], P = 0.002). However, there was no difference between 24 and 72 hours. There was no difference among the groups with respect to extubation time, nausea, vomiting, or respiratory depression. This meta-analysis concludes that there is currently insufficient evidence for the use of intraoperative methadone, when compared with other opioids. Although there was a decrease in average pain scores with methadone when compared with controls at 24 hours, there was no difference between 24 and 72 hours.

Enhanced recovery and early extubation after pediatric cardiac surgery using single-dose intravenous methadone

Background/Aims:

Methadone may offer advantages in facilitating early extubation after cardiac surgery, but very few data are available in the pediatric population.

Setting/Design:

Community tertiary children's hospital, retrospective case series.

Materials and Methods:

We performed a retrospective analysis of all pediatric cardiac surgical patients for whom early extubation was intended. A multimodal analgesic regimen was used for all patients, consisting of methadone (0.2–0.3 mg/kg), ketamine (0.5 mg/kg plus 0.25 mg/kg/h), lidocaine (1 mg/kg plus 1.5 mg/kg/h), acetaminophen (15 mg/kg), and parasternal ropivacaine (0.5 mL/kg of 0.2%). Outcome variables were collected with descriptive statistics.

Results:

A total of 24 children [median = 7 (interquartile range = 3.75–13.75) years old, 23.7 (14.8–53.4) kg] were included in the study; 22 (92%) had procedures performed on bypass and 11 (46%) involved a reentry sternotomy. Methadone dosing was 0.26 (0.23–0.29) mg/kg. None of the children required intraoperative supplemental opioids; 23 (96%) were extubated in the operating room. The first p_aCO₂ on pediatric intensive care unit admission was 51 (45–58) mmHg. Time to first supplemental opioid administration was 5.1 (3.5–9.5) h. Cumulative total supplemental opioids (in intravenous morphine equivalents) at 24 and 72 h were 0.2 (0.09–0.32) and 0.42 (0.27–0.68) mg/kg. One child required postoperative bilevel positive airway pressure support, but none required reintubation. None had pruritus; three (13%) experienced nausea.

Conclusion:

A methadone-based multimodal regimen facilitated early extubation without appreciable adverse events. Further investigations are needed to confirm efficacy of this regimen and to assess whether the excellent safety profile seen here holds in the hands of multiple providers caring for a larger, more heterogeneous population.

Methadone: applications in pediatric anesthesiology and critical care medicine

Like morphine, methadone is a pure agonist at the µ opioid receptor. However, in distinction to morphine which has an elimination half-life of 2-3 h, methadone has an elimination half-life of 24-36 h. In addition to its effects at the µ opioid receptor, methadone is an antagonist at the N-methyl-D-aspartate (NMDA) receptor and also inhibits the reuptake of the neurotransmitters, serotonin and norepinephrine, in the central nervous system. Given its long half-life and high oral bioavailability, methadone has had a primary role in the outpatient treatment of patients with a history of opioid abuse or addiction. However, its unique pharmacology and cellular effects make it a valuable agent in the treatment of both acute and chronic pain of various etiologies. The following manuscript reviews the pharmacologic properties of methadone and discusses its clinical applications in the practice of pediatric anesthesiology and pediatric critical care medicine.