Methadone Dose Research Articles

Effect of oral naloxone on opioid-induced constipation in methadone maintenance treatment patients, a double-blind, placebo-control, clinical trial.

Opioid-induced constipation (OIC) is the most prevalent side effect of methadone maintenance therapy (MMT). Naloxone could reduce the OIC. Fifty-six MMT cases (< 75mg/day methadone, > 3months) were entered randomly into four groups of a trial. They received placebo or naloxone tablets (0.5, 2, or 4mg/day) once a day for 2weeks. They continued their conventional laxative. Their constipation and opiate withdrawal (OWS) were evaluated by the Bristol Stool Form Scale (stool consistency and frequency), Patient Assessment of Constipation Symptoms (PAC-SYM) questionnaire, Constipation Scoring System (CSS), and the Subjective Opiate Withdrawal Scale (SOWS) before starting treatment and at the end of the first and second weeks. The dose of 4mg/day naloxone was excluded from the study due to severe OWS. The precipitantsof groups had similar ages, methadone dose and duration, laxative use, and constipation scores at the start of the trial. However, 2mg of naloxone could change the stool consistency (PV = 0.0052) and frequency (P = 0.0133), 0.5mg/day dose only improved the stool consistency (P = 0.0016). The patients' CSS and PAC-SYM scores were reduced by naloxone after the 1st week of treatment. However, there was no significant difference in the mean score of SOWS at different assessment times and groups. Also, 3 and 4 cases of 0.5 and 2mg/day groups, respectively, withdrew from the study due to OWS. Oral naloxone at doses of 0.5 and 2mg/day was significantly more effective than placebo on OIC in MMT. However, the dose of 4mg induced intolerable OWS.

Higher methadone dose at time of release from prison predicts linkage to maintenance treatment for people with HIV and opioid use disorder transitioning to the community in Malaysia

BackgroundIncarcerated people with HIV and opioid-dependence often experience poor post-release outcomes in the absence of methadone maintenance treatment (MMT). In a prospective trial, we assessed the impact of methadone dose achieved within prison on linkage to MMT after release. MethodsFrom 2010 to 2014, men with HIV (N = 212) and opioid dependence before incarceration were enrolled in MMT within 6 months of release from Malaysia's largest prison and followed for 12-months post-release. As a prospective trial, allocation to MMT was at random and later by preference design (predictive nonetheless). MMT dosing was individually targeted to minimally achieve 80 mg/day. Time-to-event analyses were conducted to model linkage to MMT after release. FindingsOf the 212 participants allocated to MMT, 98 (46 %) were prescribed higher dosages (≥80 mg/day) before release. Linkage to MMT after release occurred in 77 (36 %) participants and significantly higher for those prescribed higher dosages (46% vs 28 %; p = 0.011). Factors associated with higher MMT dosages were being married, on antiretroviral therapy, longer incarceration periods, having higher levels of depression, and methadone preference compared to randomization. After controlling for other variables, being prescribed higher methadone dosage (aHR: 2.53, 95 %CI: 1.42–4.49) was the only independent predictor of linkage to methadone after release. InterpretationHigher doses of methadone prescribed before release increased the likelihood of linkage to MMT after release. Methadone dosing should be introduced into international guidelines for treatment of opioid use disorder in prisons and further post-release benefits should be explored. FundingNational Institute of Drug Abuse (NIDA).

The relationship of pain intensity and opioid craving with delayed methadone dose: A preliminary study of individuals with opioid use disorder.

Despite a strong theoretical link between opioid craving and pain, little is known about the temporal relationship between pain and craving and the acute experience of pain in the context of methadone treatment. Using a cross-over design, the current study evaluated the time course of pain and craving and objective experience of pain as a function of the last methadone dose. Participants (n = 20) presented for the study in the morning and either received methadone dose as scheduled or delayed dose until the afternoon. During the 4-h study visit, participants completed a series of tasks, including repeated assessment of pain and craving at 0, +40, +70, +130, +160 and +240 min and a cold pressor test (CPT) at +15 and +220 min. Separate mixed model results demonstrated no effect of dosing condition on craving; however, there was a significant dosing condition by time interaction (F(5,209) = 3.38, P = .006) such that pain increased over time in the delayed methadone condition but decreased in time in the scheduled methadone condition. A mixed model predicting self-reported pain revealed a three-way interaction between dosing condition, craving and time (F(5,197) = 2.39, P = .039) explained by a positive association between craving and pain at each time point (except 240 min) in delayed condition (P-range = .004-.0001). A separate mixed model on CPT data indicated a significant condition by time interaction such that pain threshold decreased in the delayed, but not scheduled, condition (F(1,57) = 4.01, P = .050). These preliminary findings highlight the potential for increased risks after even a short delay in receiving a methadone dose.

Predictive Factors for Methadone Maintenance Treatment Compliance: Exploring Resistance and Tolerance in Heroin Addiction

Background: Methadone maintenance treatment (MMT) has been a cornerstone in heroin addiction management. However, its efficacy varies among individuals. The complex interplay of genetic backgrounds and demographic data could influence the response to MMT in heroin addiction. No previous adoption study has aimed to merge these findings into a potential pre-treatment screening tool. Objectives: This study aimed to investigate the combined influence of dopamine and opioid receptors and receptor endocytosis machinery genes, individual genetic backgrounds, and demographic data on the response to MMT in patients with heroin addiction. Methods: We enrolled 80 heroin addicts receiving MMT for 3 months alongside 80 healthy individuals in a comparative study. The approach utilized multinomial, linear, and binary logistic regression analyses to investigate the interplay of genetic factors (DRD1-5, opioid receptors [µ1, δ1, and κ1], DNM1L, RAB22A, and COMT), demographic independent variables, including, family history, heroin duration, age onset, heroin dose, and methadone dose, and clinical markers Subjective Opiate Withdrawal Scale (SOWS) with compliance with MMT protocols. Results: Results revealed that a positive family history and a higher level of heroin dose significantly predicted poor compliance to MMT. Additionally, the patients with lower expression levels of DRD2 and higher expression levels of DNM1L and COMT genes were at higher risk for poor compliance with the treatment. Conclusions: By utilizing a comprehensive dataset of gene expression profiles and demographic and clinical parameters, this study developed a regression model predicting resistance or response to methadone. This innovative approach seeks to bridge the gap between pharmacogenomics and clinical practice and offer a potential pre-treatment screening tool for personalized MMT strategies in opioid addiction management. The obtained findings hold intriguing promise for future research, potentially unlocking deeper insights into the underlying risk factors of addiction.

Efficacy and safety of subcutaneous methadone hydrochloride in four-toed hedgehogs (Atelerix albiventris).

To evaluate the efficacy and safety of SC methadone in four-toed hedgehogs. 9 to 12 healthy adult four-toed hedgehogs (7 to 9 males and 3 females). Hedgehogs underwent 3 randomized, blinded, placebo-controlled, complete crossover studies. Hind limb withdrawal latencies in response to an acute thermal noxious stimulus were measured to evaluate the antinociceptive efficacy of methadone. Single doses of SC methadone were evaluated at 0.5 and 1 mg/kg for dose-dependent effects. Additionally, methadone (1.5 mg/kg) was administered at different concentrations to assess the effect of injection volume on antinociceptive efficacy. Finally, the safety of multiple doses of methadone (1.5 mg/kg, SC, q 2 h, for 3 doses) was also evaluated. In addition to monitoring behavior during latency measurements, animals were assessed for overt sedation. Food intake, body weight, and running wheel activity were assessed daily for 6 days following methadone administration to evaluate for adverse effects. Methadone at 1 and 1.5 mg/kg provided antinociception lasting < 2 hours, and injection volume had no significant effect on efficacy. Methadone at 0.5 mg/kg did not induce antinociception. Methadone produced transient abnormal behaviors in all hedgehogs, with more animals affected at the 1.5-mg/kg dose. Behaviors included periods of standing motionless, vocalization, chewing motions, and paw raising. Single- or multiple-dose administration of methadone had no significant effect on total food intake, body weight, or running wheel activity. The results of this study provide additional information on providing analgesia to hedgehogs. Subcutaneous methadone (1 to 1.5 mg/kg) can be used for short-term antinociception in hedgehogs.

Experience of patients on methadone maintenance treatment receiving take-home methadone doses during COVID-19 pandemic: A multi-site study from India

BackgroundMethadone take-home doses for opioid dependence treatment are strictly regulated due to diversion and overdose concerns, so patients must visit the clinic daily for dispensing. This was also done in India until the COVID-19 pandemic, when lockdown restriction compelled take- home dispensing of methadone. This study examined experience of patients who received take- home methadone during COVID-19 pandemic in India. MethodsObservational, cross-sectional design. We contacted all consenting methadone centres in India during the lockdown and selected those that provided take-home doses for the study. Patients who received daily methadone before the lockdown and take-home doses after were interviewed using a study-specific questionnaire. ResultsThe study had 210 participants. Take-home methadone was dispensed for 2.5 days on average in each dispensing. When taking methadone at home, 3.3% split their dose 25% took less than the prescribed dose to save it for a rainy days, and 3.3% reported an overdose episode. Adherence improved in 58.6% participants after take-home methadone. Participants perceived many benefits from take-home methadone such as reduced hospital visits and travel time to collect methadone, improvement in work, and financial savings. About 54.3% participants reported storing their take-home doses safely, and 1.9% reported that their family consumed methadone by mistake. ConclusionsTake-home methadone was found to be beneficial to most participants in terms of time saved and improved productivity. Preconceived concerns of providing take-home methadone in terms of its overdose, diversion, or accidental ingestion by others are not commonly seen when individuals are provided take-home doses of methadone.

The effects of OPRM1 118A>G on methadone response in pain management in advanced cancer at end of life

Cancer pain is the most feared symptom at end of life. Methadone has advantages over other opioids but is associated with significant variability in clinical response, making dosing challenging in practice. OPRM1 is the most studied pharmacogene associated with the pharmacodynamics of opioids, however reports on the association of the A118G polymorphism on opioid dose requirements are conflicting, with no reports including methadone as the primary intervention. This association study on OPRM1 A118G and response to methadone for pain management, includes a review of this genetic factor’s role in inter-patient variability. Fifty-four adult patients with advanced cancer were recruited in a prospective, multi-centre, open label dose individualization study. Patient characteristics were not shown to influence methadone response, and no significant associations were observed for methadone dose or pain score. The findings of our review of association studies for OPRM1 A118G in advanced cancer pain demonstrate the importance of taking ancestry into account. While our sample size was small, our results were consistent with European populations, but in contrast to studies in Chinese patients, where carriers of the A118G polymorphism were associated with higher opioid dose requirements. Pharmacogenetic studies in palliative care are challenging, continued contribution will support future genotype-based drug dosing guidelines.

The Effect of HCV on Methadone Dose During Pregnancy

The Effect of HCV on Methadone Dose During Pregnancy

Methadone Take-Home Policies and Associated Mortality: Permitting versus Non-Permitting States.

To mitigate COVID-19 exposure risks in methadone clinics, the Substance Abuse and Mental Health Services Administration (SAMHSA) issued a temporary modification of regulations in March 2020 to permit, with state concurrence, extended take-home methadone doses. The modification allowed for up to 28 days of take-home methadone for stable patients and 14 days for those less stable. Using both interrupted time series and difference-in-differences methods, this study examined the association between the policy change and fatal methadone overdoses, comparing states that permitted the expansion of take-home doses with states that did not. The findings suggest the pandemic emergency take-home policy did not increase methadone-involved mortality.

Buprenorphine induction using microdosing for the management of opioid use disorder in pregnancy

Conventional buprenorphine inductions require patients to abstain from full agonist opioids until they experience mild to moderate opioid withdrawal. We describe a successful buprenorphine induction case in a pregnant patient using microdosing, which avoided withdrawal symptoms. Case: The patient is a 29 year old G2P1001 at 18 2/7 weeks of gestation, who desired a switch from methadone to buprenorphine to minimize neonatal opioid withdrawal syndrome (NOWS), which complicated her last pregnancy. She was given increasing microdoses of buprenorphine over a 7 day period, while continuing her daily dose of methadone. She discontinued the methadone on day 8. She did well during the week of buprenorphine microdosing, with no complaints of withdrawal or cravings. She was engaged in her prenatal care. Her dose of buprenorphine was increased to 8 mg bid in the third trimester for some withdrawal symptoms in the evening consisting of new onset nausea and vomiting. The patient underwent an elective 39 week induction of labor and had a spontaneous vaginal delivery of an appropriately grown male fetus. Only non-pharmacologic interventions were used. Conclusion: Buprenorphine microdosing was well tolerated in this patient and avoided withdrawal symptoms in the mothers, and NOWS. A microdosing study in pregnancy is indicated

Medications for opioid use disorder associated with reduced readmissions for patients with severe injection-related infections: A matched cohort study

IntroductionHospitalizations due to severe injection-related infections (SIRIs) and patient-directed discharge (PDD) in people who inject drugs (PWID) are increasing, but research on readmission outcomes at PDD is limited. In this retrospective, matched cohort study we evaluated predictors of 30-day readmission by discharge status among PWID. MethodsAmong patients diagnosed with SIRIs at a tertiary hospital, Fisher's exact tests assessed differences in readmission rates by discharge status. Medications for opioid use disorder (MOUD) at discharge was defined as either having a buprenorphine dose dispensed within 24 h of discharge and buprenorphine being included in the discharge summary as a prescription, or a methadone dose dispensed inpatient within 24 h of discharge. Logistic regression analyses evaluated predictors of readmission outcomes. ResultsAmong 148 PWID with SIRI diagnosis, 30-day readmission rate following PDD was higher than standard discharge (25.7 % vs. 9.5 %, p = 0.016) and MOUD decreased odds of 30-day readmission (OR = 0.32, 95 % CI: 0.12,0.83, p = 0.012). >7 missed days of antibiotic treatment increased odds of 30-day readmission (OR 4.65, 95 % CI: 1.14, 31.72, p = 0.030) within PDD patients. ConclusionsPDD carries higher 30-day readmission rate compared to standard discharge. Strategies to reduce PDD rates and increase MOUD initiation may improve readmission outcomes.

Methadone pharmacokinetics in opioid agonist treatment: Influencing factors and clinical implications.

A considerable inter-individual variability has been reported in the relationship between methadone doses applied and serum concentrations achieved in methadone maintenance treatment. However, the underlying causes for this variability are not fully understood. We investigated the influence of genetic, pathophysiological and pharmacological factors on serum methadone concentration-to-dose ratio (CDR) and discussed the clinical implications of the findings. We used data from two retrospective laboratory databases and a prospective cohort study to investigate the impact on methadone CDR of hepatic cytochrome P450 enzyme system (CYP) genetic polymorphisms, age, sex, concomitant medication, liver fibrosis and body mass index through linear mixed model analyses. A positive association was found between CDR and the homozygous CYP2B6*6 genotype, concurrent treatment with CYP3A4 inhibitors and body mass index. CDR was lower among women and during concomitant use of CYP inducers. CDR was not associated with age or the degree of liver fibrosis in our investigations. This research work supports the need for individually tailored dosage considering the various factors that influence methadone CDR. The gained knowledge can contribute to reducing the risks associated with the treatment and optimizing the desired outcomes.

Optimizing methadone dose adjustment in patients with opioid use disorder.

Opioid use disorder is a cause for concern globally. This study aimed to optimize methadone dose adjustments using mixed modeling and machine learning. This retrospective study was conducted at Taichung Veterans General Hospital between January 1, 2019, and December 31, 2020. Overall, 40,530 daily dosing records and 1,508 urine opiate test results were collected from 96 patients with opioid use disorder. A two-stage approach was used to create a model of the optimized methadone dose. In Stage 1, mixed modeling was performed to analyze the association between methadone dose, age, sex, treatment duration, HIV positivity, referral source, urine opiate level, last methadone dose taken, treatment adherence, and likelihood of treatment discontinuation. In Stage 2, machine learning was performed to build a model for optimized methadone dose. Likelihood of discontinuation was associated with reduced methadone doses (β = 0.002, 95% CI = 0.000-0.081). Correlation analysis between the methadone dose determined by physicians and the optimized methadone dose showed a mean correlation coefficient of 0.995 ± 0.003, indicating that the difference between the methadone dose determined by physicians and that determined by the model was within the allowable range (p < 0.001). We developed a model for methadone dose adjustment in patients with opioid use disorders. By integrating urine opiate levels, treatment adherence, and likelihood of treatment discontinuation, the model could suggest automatic adjustment of the methadone dose, particularly when face-to-face encounters are impractical.

Methadone for Emergence Delirium in Ambulatory Pediatric Strabismus Surgery.

Background: Emergence delirium in children following strabismus surgery is a distressing and potentially dangerous condition and is likely attributable to visual disturbances, pain, and anesthetic gases. We explored whether a single intraoperative dose of methadone could reduce emergence delirium. Methods: Our study was an institutional review board-approved prospective, controlled, before-and-after investigation. Inclusion criteria were age <18 years and American Society of Anesthesiologists (ASA) classification 1 or 2. Patients were excluded for obesity, documented sleep apnea, significant neurologic disease, or inpatient status. Control group patients were recruited sequentially, and the anesthetic was performed per preference. The study group was recruited similarly and received an intravenous dose of methadone 0.15 mg/kg at induction. The primary outcome was peak score on the Pediatric Anesthesia Emergence Delirium (PAED) scale. Secondary outcomes included time to anesthetic emergence, postoperative pain scores, postanesthesia care unit (PACU) length of stay, and postdischarge respiratory complications. Results: Forty-nine control group and 55 study group patients were recruited. No significant differences were found between groups for age, sex, weight, ASA classification, or duration of surgery. The control group received more preoperative midazolam, intraoperative fentanyl, and intraoperative ketorolac. Compared to the control group, the study group had 42% and 85% reductions in peak and severe PAED scale scores, respectively, in the PACU and required less rescue pain medications. Anesthetic emergence time and length of stay were not different between the groups. No significant postoperative complications occurred. Conclusion: Emergence delirium following outpatient pediatric strabismus surgery was substantially mitigated by the use of intraoperative methadone without affecting PACU throughput. No significant complications occurred. Further study is warranted to corroborate routine use of this drug for emergence delirium.

Prevalence of Delirium and Its Related Factors in Burn Patients; a Systematic Review and Meta-Analysis.

Considering the importance of delirium disorder in burn patients and its complications, the present systematic review and meta-analysis aimed to determine the prevalence of delirium and its related factors in burn patients. A comprehensive, systematic search was performed in different international electronic databases, such as Scopus, PubMed, and Web of Science, as well as Persian electronic databases such as Iranmedex, and Scientific Information Database (SID) using keywords extracted from Medical Subject Headings such as "Prevalence", "Delirium", and "Burns" from the earliest to the 17th of July, 2023. In total, 2,710 burn patients participated in ten original studies. Among the participants, 64.6% were male. In the ten studies, the reported pooled prevalence of delirium among burn patients was 20.5% (95% CI: 10.9% to 35.0%; I2=96.889%; P<0.001). Also, factors such as total body surface area, duration of hospitalization, mortality, days on ventilator, alcoholism, benzodiazepine dose, methadone dose, age, male gender, ICU days, operation days, wound care under anesthesia, and opioid dose had a significant correlation with the prevalence of delirium in burn patients. Health managers and policymakers can reduce the prevalence of delirium in burn patients by eliminating or reducing factors associated with it.

497 Fetal Heart Tracing Changes at Peak Methadone or Buprenorphine Dose Appear Unrelated to NOWS Severity

497 Fetal Heart Tracing Changes at Peak Methadone or Buprenorphine Dose Appear Unrelated to NOWS Severity

Methadone and neonatal abstinence syndrome (NAS): what we think we know, but do not.

Since the first use of methadone to treat OUD in pregnancy in the 1970s, there has been a long, controversial, and confusing history of studies, regulatory actions, and practice changes that have clouded an accurate perception of methadone's use in pregnancy. This review will trace this history with a focus on the effect of methadone exposure during pregnancy on neonatal abstinence syndrome (NAS). A new laboratory measure, the serum methadone/metabolite ratio (MMR), has provided a tool for documenting the profoundly dynamic nature of perinatal metabolism. Continuous induction of metabolic enzymes during pregnancy requires dose adjustments and dose frequency changes. The concept of "fetal methadone dosing" emphasizes that relative stability of methadone levels in the fetus is an important consideration for methadone dosing in pregnancy. Finally, the effects of the societal "war on drugs" on pediatric management of neonatal withdrawal risks will be discussed, as well as the importance of comprehensive services for mother and child including the "rooming-in" approach of neonatal care which has considerably replaced the older NICU care model of maternal/infant separation.

A genome-wide association, polygenic risk score and sex study on opioid use disorder treatment outcomes

Opioid use disorder continues to be a health concern with a high rate of opioid related deaths occurring worldwide. Medication Assisted Treatments (MAT) have been shown to reduce opioid withdrawal, cravings and opioid use, however variability exists in individual’s treatment outcomes. Sex-specific differences have been reported in opioid use patterns, polysubstance use and health and social functioning. Candidate gene studies investigating methadone dose as an outcome have identified several candidate genes and only five genome-wide associations studies have been conducted for MAT outcomes. This study aimed to identify genetic variants associated with MAT outcomes through genome-wide association study (GWAS) and test the association between genetic variants previously associated with methadone dose through a polygenic risk score (PRS). Study outcomes include: continued opioid use, relapse, methadone dose and opioid overdose. No genome-wide significance SNPs or sex-specific results were identified. The PRS identified statistically significant results (p < 0.05) for the outcome of methadone dose (R2 = 3.45 × 10–3). No other PRS was statistically significant. This study provides evidence for association between a PRS and methadone dose. More research on the PRS to increase the variance explained is needed before it can be used as a tool to help identify a suitable methadone dose within this population.

Operationalizing the new DEA exception: A novel process for dispensing of methadone for opioid use disorder at discharge from acute care settings.

To describe one strategy for dispensing of methadone at emergency department (ED) and hospital discharge implemented within 2 urban academic medical centers. Expanding access to medications for opioid use disorder (OUD) is a national priority. ED visits and hospitalizations offer an opportunity to initiate or continue these lifesaving medications, including methadone and buprenorphine. However, federal regulations governing methadone treatment and significant gaps in treatment availability have made continuing methadone upon ED or hospital discharge challenging. To address this issue, the Drug Enforcement Administration (DEA) granted an exception allowing hospitals, clinics, and EDs to dispense a 72-hour supply of methadone while continued treatment is arranged. Though this exception addresses a critical unmet need, guidance for operationalizing this service is limited. To facilitate expanded patient access to methadone on ED or hospital discharge at 2 Baltimore hospitals, key stakeholders within the parent health system were identified, and a workgroup was formed. Processes were established for requesting, approving, preparing, and dispensing the methadone supply using an electronic health record order set. Multidisciplinary educational materials were created to support end users of the workflow. In the first 3 months of implementation, 42 requests were entered, of which 36 were approved, resulting in 79 dispensed methadone doses. This project demonstrates feasibility of methadone dispensing at hospital and ED discharge. Further work is needed to evaluate impact on patient outcomes, such as hospital and ED utilization, length of stay, linkage to treatment, and retention in treatment.

Perioperative analgesic efficacy of lumbar erector spinae plane block in dogs undergoing hemilaminectomy: a randomized blinded clinical trial

ObjectiveTo evaluate the perioperative analgesic effect of the unilateral lumbar erector spinae plane block (ESPBL) in dogs undergoing hemilaminectomy. Study designRandomized, blinded clinical study. AnimalsA total of 30 client-owned dogs undergoing thoracolumbar or lumbar hemilaminectomy for intervertebral disc extrusion (IVDE). MethodsDogs were randomly assigned to receive a unilateral ESPBL, performed either with 0.4 mL kg−1 ropivacaine 0.5% [group ROPI (n = 15)] or with saline solution [CNT group (n = 15)]. Dogs were premedicated intravenously (IV) with acepromazine 5 μg kg−1 and methadone 0.2 mg kg−1, general anaesthesia was induced by administering IV midazolam 0.2 mg kg−1 and propofol to effect and maintained with isoflurane. Fentanyl was administered as rescue analgesia. Bradycardia [heart rate (HR) < 60 beats minute−1] with hypotension was treated with atropine IV. The Short-Form of the Glasgow Composite Pain Scale was used pre- and postoperatively at 1, 2, 4, 8, 12, 16, 20 and 24 hours after extubation, and methadone 0.2 mg kg−1 was administered IV when pain score was ≥ 5/20. HR and end-tidal concentration of isoflurane (Fe'Iso) were compared between groups with anova combined with a Dunnet’s post hoc test. Time to the first rescue methadone and total dose of fentanyl (FENtot, μg kg−1 hour−1) and methadone (METtot, mg kg−1) in the first 24 postoperative hours were compared using unpaired Student’s t test. Postoperative pain scores were compared with the Mann–Whitney test and atropine administration with a Fisher’s exact test; p < 0.05. ResultsHR, Fe'Iso, FENtot, METtot and atropine administration were significantly lower in group ROPI compared to CNT. Postoperative analgesic effect was significantly longer, and pain scores were significantly lower in group ROPI for all time points. Conclusions and clinical relevanceUnilateral ESPBL with ropivacaine reduced perioperative opioid consumption and the occurrence of bradycardia in dogs undergoing hemilaminectomy.