The effect of methylnaltrexone on the side effects of intrathecal morphine after orthopedic surgery under spinal anesthesia

Methylnaltrexone in the Management of Opioid-Associated Urinary Retention in Children

OBJECTIVE

To evaluate the association between methylnaltrexone and urine output (UOP) in critically ill children with opioid-associated urinary retention.

METHODS

This retrospective study included patients admitted to the pediatric intensive care unit between December 1, 2019, and November 30, 2020, who received methylnaltrexone for opioid-associated oliguria (spontaneous UOP below 1 mL/kg/hr and at least 1 dose of an opioid within the preceding 6 hours).

RESULTS

Twenty-five patients (median age = 5.5 years, IQR 1.7–16.4; median weight = 19 kg, IQR 9–45) were included. Mean methylnaltrexone dose was 0.15 ± 0.006 mg/kg. A statistically significant increase in UOP from baseline to 6 hours following methylnaltrexone was observed (p = 0.001), but not all patients responded. Fourteen patients (56%) had no UOP following methylnaltrexone administration, while 11 (44%) demonstrated a robust increase (median = 0 mL/kg/hr at baseline [IQR 0–0] to 1.96 mL/kg/hr [IQR 1.08–2.22; p = 0.001]) within 6 hours following methylnaltrexone administration. Younger patients responded better than older patients (responder age = 2.5 years [IQR 0.8–7]) versus 11.4 years [IQR 1.75–17.5] for non-responders) (p = 0.04). Both intravenous (IV) and subcutaneous (SQ) routes were associated with an increase in UOP (IV, p = 0.04; SQ, p = 0.02). The effect persisted for up to 24 hours after administration. Sixty-four percent of patients required urinary catheter placement. Pain scores (averaged 6 hours before and after methylnaltrexone) remained unchanged (p = 0.44).

CONCLUSIONS

Methylnaltrexone may increase spontaneous UOP in some children with opioid-associated urinary retention, but urinary catheterization rates remain high.

Medical and non-medical interventions for post-operative urinary retention prevention: network meta-analysis and risk-benefit analysis

Aims

To assess the efficacy in lowering post-operative urinary retention, urinary tract infection and lower urinary tract symptoms and the incidence of adverse events among 12 interventions and to perform risk-benefit analysis.

Methods

Previous randomized controlled trials were identified from MEDLINE, Scopus and CENTRAL database up to January 2020. The interventions of interest included early ambulation, fluid adjustment, neuromodulation, acupuncture, cholinergic drugs, benzodiazepine, antispasmodic agents, opioid antagonist agents, alpha-adrenergic antagonists, non-steroidal anti-inflammatory drugs (NSAIDs) and combination of any interventions. The comparators were placebo or standard care or any of these interventions. Network meta-analysis was performed. The probability of being the best intervention was estimated and ranked using rankogram and surface under the cumulative ranking curve. Risk-benefit analysis was done. Incremental risk-benefit ratio (IRBR) was calculated and risk-benefit acceptability curve was constructed.

Results

A total of 45 randomized controlled trials with 5387 patients was included in the study. Network meta-analysis showed that early ambulation, acupuncture, alpha-blockers and NSAIDs significantly reduced the post-operative urinary retention. Regarding urinary tract infection and lower urinary tract symptoms, no statistical significance was found among interventions. Regarding the side effects, only alpha-adrenergic antagonists significantly increased the adverse events compared with acupuncture and opioid antagonist agents from the indirect comparison. According to the cluster ranking plot, acupuncture and early ambulation were considered high efficacy with low adverse events, corresponding to the IRBR.

Conclusion

Early ambulation, acupuncture, opioid antagonist agents, alpha-adrenergic antagonists and NSAIDs significantly reduce the incidence of post-operative urinary retention with no difference in adverse events. Regarding the risk-benefit analysis of the medical treatment, alpha-adrenergic antagonists have the highest probability of net benefit at the acceptable threshold of side effect of 15%, followed by opioid antagonist agents, NSAIDs and cholinergic drugs.

Preoperative Management of Opioid and Nonopioid Analgesics: Society for Perioperative Assessment and Quality Improvement (SPAQI) Consensus Statement

There is a lack of guidelines for preoperative dosing of opioid and nonopioid pain medications for surgical patients, which can lead to suboptimal preoperative pain control. The Society for Perioperative Assessment and Quality Improvement identified preoperative dosing of opioid and nonopioid analgesics as an area in which consensus could improve patient care. The aim of this guideline is to provide consensus that will allow perioperative physicians to make optimal recommendations regarding preoperative pain medication dosing. Six categories of pain medications were identified: opioid agonists, opioid antagonists, opioid agonist-antagonists, acetaminophen, muscle relaxants, and triptans/headache medications. We then used a Delphi survey technique to develop consensus recommendations for preoperative dosing of individual medications in each of these groups.

Identifying and Treating Opioid Side Effects: The Development of Methylnaltrexone

Methylnaltrexone Reverses Chronic Opioid-induced Constipation: A Randomized, Controlled Trial. By Yuan CS, Foss JF, O'Connor M, Osinski J, Karrison T, Moss J, Roizen MF. JAMA 2000; 130:142-8. Reprinted with permission.

CONTEXT

Constipation is the most common chronic adverse effect of opioid pain medications in patients who require long-term opioid administration, such as patients with advanced cancer, but conventional measures for ameliorating constipation often are insufficient.

OBJECTIVE

To evaluate the efficacy of methylnaltrexone, the first peripheral opioid receptor antagonist, in treating chronic methadone-induced constipation.

DESIGN

Double-blind, randomized, placebo-controlled trial conducted between May 1997 and December 1998.

SETTING

Clinical research center of a university hospital.

PARTICIPANTS

Twenty-two subjects (9 men and 13 women; mean [SD] age, 43.2 [5.5] years) enrolled in a methadone maintenance program and having methadone-induced constipation.

MAIN OUTCOME MEASURES

Laxation response, oral-cecal transit time, and central opioid withdrawal symptoms were compared between the 2 groups.

RESULTS

The 11 subjects in the placebo group showed no laxation response, and all 11 subjects in the intervention group had laxation response after intravenous methylnaltrexone administration (P<.001). The oral-cecal transit times at baseline for subjects in the methylnaltrexone and placebo groups averaged 132.3 and 126.8 minutes, respectively. The average (SD) change in the methylnaltrexone-treated group was -77.7 (37.2) minutes, significantly greater than the average change in the placebo group (-1.4 [12.0] minutes; P<.001). No opioid withdrawal was observed in any subject, and no significant adverse effects were reported by the subjects during the study.

CONCLUSIONS

Our data demonstrate that intravenous methylnaltrexone can induce laxation and reverse slowing of oral cecal-transit time in subjects taking high opioid dosages. Low-dosage methylnaltrexone may have clinical utility in managing opioid-induced constipation.

Nalbuphine Reduces Opioid-Associated Urinary Retention in Pediatric Patients

OBJECTIVES

To evaluate the effect of nalbuphine administration on urine output in critically ill children with opioid-associated urinary retention.

DESIGN

Institutional review board approved, single center, retrospective medical chart review.

SETTING

Large medical-surgical PICU within a free-standing, tertiary care children's hospital.

PATIENTS

Patients admitted to the PICU between October 1, 2014, and February 29, 2016, who received IV nalbuphine after meeting criteria for opioid-associated oliguria (defined as urine output below 1 mL/kg/hr and received at least one dose of opioid therapy within the preceding 12 hr).

INTERVENTIONS

None.

MEASUREMENT AND MAIN RESULTS

Seventeen patients who received 21 doses of nalbuphine were analyzed. The median age and weight of patients were 6 years (interquartile range, 3-11.5 yr) and 18 kg (interquartile range, 12-35 kg), respectively. Two distinct dosing strategies became evident, specifically 0.05 mg/kg (n = 11 doses) and 0.1 mg/kg (n = 10 doses). Urine output increased significantly from baseline (median, 0 mL/kg/hr; interquartile range, 0-0.53 mL/kg/hr) to 6 hours post nalbuphine administration (median, 1.48 mL/kg/hr; interquartile range, 0-2 mL/kg/hr; p = 0.0002). Patients who received 0.1 mg/kg/dose had a greater urine output response compared with those who received 0.05 mg/kg/dose. Five patients (29%) had a catheter inserted into their bladder after administration of nalbuphine. Pain scores (grouped 6 hr before and after nalbuphine administration and single pain scores documented immediately before and after nalbuphine administration) were unchanged.

CONCLUSIONS

Nalbuphine administration, at a dose of 0.1 mg/kg, improved urine output in a cohort of children with opioid-associated urinary retention. Pain control did not appear influenced by the provision of nalbuphine. Additional studies are needed to determine the influence of nalbuphine on urinary catheter insertion rates and catheter-associated urinary tract infections.

Systematic review of interventions for the prevention and treatment of postoperative urinary retention

Background

Postoperative urinary retention (PO‐UR) is an acute and painful inability to void after surgery that can lead to complications and delayed hospital discharge. Standard treatment with a urinary catheter is associated with a risk of infection and can be distressing, undignified and uncomfortable. This systematic review aimed to identify effective interventions for the prevention and treatment of PO‐UR that might be alternatives to urinary catheterization.

Methods

Electronic databases were searched from inception to September 2017. Randomized trials of interventions for the prevention or treatment of PO‐UR were eligible for inclusion. Studies were assessed for risk of bias using the Cochrane (2.0) tool. Two reviewers were involved at all review stages. Where possible, data were pooled using random‐effects meta‐analysis. The overall quality of the body of evidence was rated using the GRADE approach.

Results

Some 48 studies involving 5644 participants were included. Most interventions were pharmacological strategies to prevent PO‐UR. Based on GRADE, there was high‐certainty evidence to support replacing morphine in a regional anaesthetic regimen, using alpha‐blockers (number needed to treat to prevent one case of PO‐UR (NNT) 5, 95 per cent c.i. 5 to 7), the antispasmodic drug drotaverine (NNT 9, 7 to 30) and early postoperative mobilization (NNT 5, 4 to 8) for prevention, and employing hot packs or gauze soaked in warm water for treatment (NNT 2, 2 to 4). Very few studies reported on secondary outcomes of pain, incidence of urinary tract infection or duration of hospital stay.

Conclusion

Promising interventions exist for PO‐UR, but they need to be evaluated in randomized trials investigating comparative clinical and cost effectiveness, and acceptability to patients.

Endogenous Opiates and Behavior: 2015

This paper is the thirty-eighth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2015 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia, stress and social status, tolerance and dependence, learning and memory, eating and drinking, drug abuse and alcohol, sexual activity and hormones, pregnancy, development and endocrinology, mental illness and mood, seizures and neurologic disorders, electrical-related activity and neurophysiology, general activity and locomotion, gastrointestinal, renal and hepatic functions, cardiovascular responses, respiration and thermoregulation, and immunological responses.

Prophylactic Ondansetron for the Prevention of Intrathecal Fentanyl- or Sufentanil-Mediated Pruritus: A Meta-Analysis of Randomized Trials

BACKGROUND

Pruritus is a common side effect of intrathecal fentanyl or sufentanil that decreases patient satisfaction and may delay hospital discharge. There are conflicting reports about the efficacy of prophylactic ondansetron in reducing the incidence of pruritus. This meta-analysis aimed to assess the effect of prophylactic ondansetron on the incidence of intrathecal fentanyl- or sufentanil-mediated pruritus and the need for rescue treatment.

METHODS

A systematic search on PubMed, Medline, and the Cochrane Central Register of Controlled Trials from January 1, 1994, to January 1, 2014, was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. Randomized controlled trials evaluating the efficacy of prophylactic ondansetron on pruritus associated with intrathecal fentanyl or sufentanil were included. The primary outcome was the incidence of pruritus, and the secondary outcome was patients' need for rescue therapy. Sensitivity analyses were conducted to assess the outcomes in obstetric and nonobstetric patients and in patients who received ondansetron before or after intrathecal opioid injection. Analyses used random-effect models.

RESULTS

Six randomized controlled trials involving 555 patients were included. In the overall analysis, prophylactic ondansetron did not significantly decrease the incidence of pruritus, but there was a trend toward reduced rescue medication use (risk ratio [RR], 0.57; 95% confidence interval [CI], 0.35-0.91; I = 0%; P = 0.02). Exploratory subgroups, including nonobstetric surgery patients and patients who received ondansetron before spinal opioid administration, also suggest a trend toward less rescue medication use (RR, 0.47; 95% CI, 0.26-0.85; P = 0.01; and RR, 0.62; 95% CI, 0.38-1.00; P = 0.05).

CONCLUSIONS

IV 8 mg prophylactic ondansetron does not decrease the incidence of fentanyl- or sufentanil-mediated pruritus but may decrease the need for pruritus rescue medication, particularly in specific subgroups. Randomized trials are needed to confirm these results.

Evaluation of N-substituent structural variations in opioid receptor profile of LP1

The benzomorphan scaffold has great potential as lead structure and the nature of the N-substituent is able to influence affinity, potency, and efficacy at all three opioid receptors. Building upon these considerations, we synthesized a new series of LP1 analogues by introducing naphthyl or heteroaromatic rings in propanamide side chain of its N-substituent (9-15). In vitro competition-binding assays in HEK293 cells stably expressing MOR, DOR or KOR showed that in compound 9 the 1-naphthyl ring led to the retention of MOR affinity (Ki(MOR)=38±4nM) displaying good selectivity versus DOR and KOR. In the electrically stimulated GPI, compound 9 was inactive as agonist but produced an antagonist potency value (pA2) of 8.6 in presence of MOR agonist DAMGO. Moreover, subcutaneously administered it antagonized the antinociceptive effects of morphine with an AD50=2.0mg/kg in mouse-tail flick test. Modeling studies on MOR revealed that compound 9 fit very well in the binding pocket but in a different way in respect to the agonist LP1. Probably the replacement of its N-substituent on the III, IV and V TM domains reflects an antagonist behavior. Therefore, compound 9 could represent a potential lead to further develop antagonists as valid therapeutic agents and useful pharmacological tools to study opioid receptor function.

Methylnaltrexone: its pharmacological effects alone and effects on morphine in healthy volunteers

RATIONALE

Methylnaltrexone bromide (MTNX) is a peripherally acting mu-opioid receptor antagonist, prescribed for the treatment of opioid-induced constipation in patients with advanced illness who are receiving palliative care. Studies have used this drug to determine if other opioid-induced effects besides constipation are altered by MTNX in humans and have suggested, based on their results, that these other effects are altered by peripheral opioid actions.

OBJECTIVE

The primary objective of this report is to present results that provide indirect evidence that MTNX has centrally mediated effects, albeit slight, and secondarily to describe the effects of MTNX on psychopharmacological effects of morphine.

METHODS

In a crossover, randomized, placebo-controlled, double-blind study, 29 healthy volunteers received 0.45 mg/kg MTNX or saline subcutaneously, followed by saline intravenously. In three other conditions, 0.143 mg/kg of morphine sulfate administered intravenously was preceded by subcutaneous administration of 0, 0.225, or 0.45 mg/kg MTNX. Before and after drug administration, subjective and physiological measures, including pupil diameter, were assessed.

RESULTS

Two separate analyses confirmed that 0.45 mg/kg MTNX alone induced a slight degree of miosis, a centrally mediated opioid agonist effect. This dose had minimal subjective effects. MTNX at either or both the 0.225 and 0.45 mg/kg dose reduced some subjective effects of morphine without altering miosis.

CONCLUSIONS

We present indirect evidence that MTNX crosses the blood-brain barrier in humans. Therefore, whether the reductions in subjective effects of morphine by MTNX that were observed in past studies and in this study can be attributed to peripheral mechanisms is open to question.