A randomized clinical trial of the effects of ultra-low-dose naloxone infusion on postoperative opioid requirements and recovery

Different doses of nalmefene combined with hydromorphone hydrochloride for postoperative analgesia after colorectal surgery: a randomized controlled study

BACKGROUND

Hydromorphone hydrochloride has a satisfactory postoperative analgesic effect for patients with colorectal cancer but is accompanied by a relatively high incidence of adverse events. Low-doses of naloxone combined with opioids for patient-controlled analgesia can reduce the incidence of drug-related adverse events. Nalmefene is a more selective opioid receptor antagonist than naloxone. The aim of this study was to determine the impact of low-doses of nalmefene on the analgesic effect and incidence of adverse events of patients with hydromorphone patient-controlled analgesia (PCA) undergoing colorectal radical surgery.

METHODS

Ninety-nine patients undergoing elective laparoscopic or hand-assisted laparoscopic radical surgery under general anaesthesia were randomly divided into three groups. Group N1 received hydromorphone hydrochloride 0.15 mg/kg + nalmefene 2 µg/kg; Group N2 received hydromorphone hydrochloride 0.15 mg/kg + nalmefene 0.5 µg/kg; and the control group (Group C) received hydromorphone hydrochloride 0.15 mg/kg. All medications were diluted to 100 ml with normal saline. The primary outcome was pain intensity at 12 h after surgery; the secondary outcomes were the occurrence of nausea, vomiting and pruritus and the total analgesic consumption of the PCA pump at 1 h, 6 h, 12 h, 24 and 48 h after surgery.

RESULTS

The NRS scores of Group N1 (2 µg/kg) were significantly lower than those of Group C (P = 0.025), and no difference was found between group N2 and group C (P > 0.05). Among the three groups, the NRS scores of Group N1 (2 µg/kg) were significantly lower than those of Group C at 12 h (P = 0.01) and 48 h (P = 0.01) postoperatively. Compared with 12 h postoperatively, the NRS scores were lower at 24 h postoperatively in Group N1 and Group C (P < 0.05) and significantly lower at 48 h postoperatively in all three groups (P < 0.001). There was a significant difference in the incidence of pruritus among the three groups (P = 0.036).

CONCLUSIONS

Nalmefene at a dosage of 2 µg/kg enhances the postoperative analgesic effect of hydromorphone hydrochloride and reduces the occurrence of postoperative pruritus.

TRIAL REGISTRATION

The trial was registered with the Chinese Clinical Trial Registry (Registration number: ChiCTR2000033520, date: 03/06/2020).

Naloxone could limit morphine hypersensitivity: Considering the molecular mechanisms

BACKGROUND

Naloxone has been used as an opioid antagonist to prevent multiple adverse side effects of opioid-like tolerance and hyperalgesia. This study has investigated naloxone combined with morphine to limit pain hypersensitivity. In addition, the expression of brain-derived neurotrophic factor (BDNF) and K⁺ Cl^- cotransporter2 (KCC2) were also studied.

METHODS

Forty-eight adult male Wistar rats (180-220 g) were divided into eight groups, with six rats in each group. Rats were divided into two tolerance and hyperalgesia groups; the sham group, the morphine group, the treatment group (naloxone along with morphine), and the sham group (naloxone along with saline) for eight consecutive days. Tail-flick test was performed on days 1, 5, and 8, and the plantar test on days 1 and 10. On days 8 and 10, the lumbar segments of the spinal cord were collected, and BDNF and KCC2 expression were analyzed using western blotting and immunohistochemistry, respectively.

RESULTS

Results showed that tolerance and hyperalgesia developed following eight days of repeated morphine injection. BDNF expression significantly increased, but KCC2 was downregulated. Co-administration of naloxone and morphine decreased tolerance and hyperalgesia by decreasing BDNF and increasing KCC2 expression, respectively.

CONCLUSION

This study suggests that BDNF and KCC2 may be candidate molecules for decreased morphine tolerance and hyperalgesia.

Effects of dezocine on morphine tolerance and opioid receptor expression in a rat model of bone cancer pain

BACKGROUND

Clinically, the coadministration of opioids to enhance antinociception and decrease tolerance has attracted increasing research attention. We investigated the effects of dezocine, a mu- and kappa-opioid receptor agonist/antagonist, on morphine tolerance and explored the involvement of opioid receptor expression in a rat model of bone cancer pain.

METHODS

Thermal nociceptive thresholds were measured after the subcutaneous injection of morphine (10 mg/kg) alone or combined with dezocine (10 or 1 mg/kg) for 7 consecutive days. Real-time PCR and western blot analysis were used to examine opioid receptor expression in the periaqueductal gray (PAG) and spinal cord.

RESULTS

The analgesic effect was significantly decreased after 4 days of morphine administration. We observed that low-dose dezocine significantly attenuated morphine tolerance without reducing the analgesic effect of morphine. Low-dose dezocine coadministration significantly reversed the downregulated expression of mu (MOR) and delta (DOR) opioid receptors in the PAG and the upregulated expression of kappa (KOR) and DOR in the spinal cord induced by morphine. Moreover, low-dose dezocine coadministered with morphine significantly inhibited KOR expression in both the PAG and spinal cord.

CONCLUSIONS

The combination of low-dose dezocine with morphine may prevent or delay the development of morphine tolerance in a rat model of bone cancer pain. The regulation of opioid receptor expression in the PAG and spinal cord may be part of the mechanism.

Opioid-Sparing Effect of Liposomal Bupivacaine and Intravenous Acetaminophen in Colorectal Surgery

BACKGROUND

This study evaluated the opioid-sparing effect of liposomal bupivacaine and intravenous acetaminophen in colorectal surgery.

MATERIALS AND METHODS

This study was a retrospective, 2 × 2 factorial cohort conducted at an academic medical center from May 2016 to February 2018. Patients undergoing open or minimally invasive colorectal resection were included. Exclusion criteria were age <18 y, surgery after second hospital day, ostomy, and allergy to acetaminophen, opioids, or bupivacaine. Intraoperative liposomal bupivacaine and intravenous acetaminophen administration within 18 h after surgery were evaluated. The primary outcome was intravenous morphine milligram equivalents administered within 24 h after surgery. A linear regression model adjusted for American Society of Anesthesiologists score, enhanced recovery after surgery management, open surgery, opioid use before surgery, and height was used for the primary analysis.

RESULTS

Among 486 included patients, 193 received both liposomal bupivacaine and intravenous acetaminophen, 93 received liposomal bupivacaine only, 104 received intravenous acetaminophen only, and 96 did not receive either. On average, patients received 21 (SD = 31) morphine equivalents over 24 h. Intraoperative liposomal bupivacaine was associated with a reduction of morphine equivalents (adjusted change -11, 95% CI -17 to -6), but intravenous acetaminophen was not (2, 95% CI -3 to 7). Intraoperative liposomal bupivacaine was associated with a reduction of length of stay (adjusted change = -1.2 d, 95% CI -2.1 to -0.3), but intravenous acetaminophen was not (adjusted change = 1.5 d, 95% CI 0.7 to 2.2).

CONCLUSIONS

Liposomal bupivacaine was associated with a significant reduction of opioid use within 24 h after colorectal surgery, but intravenous acetaminophen was not.

Low-Dose Naltrexone (LDN)-Review of Therapeutic Utilization

Naltrexone and naloxone are classical opioid antagonists. In substantially lower than standard doses, they exert different pharmacodynamics. Low-dose naltrexone (LDN), considered in a daily dose of 1 to 5 mg, has been shown to reduce glial inflammatory response by modulating Toll-like receptor 4 signaling in addition to systemically upregulating endogenous opioid signaling by transient opioid-receptor blockade. Clinical reports of LDN have demonstrated possible benefits in diseases such as fibromyalgia, Crohn’s disease, multiple sclerosis, complex-regional pain syndrome, Hailey-Hailey disease, and cancer. In a dosing range at less than 1 μg per day, oral naltrexone or intravenous naloxone potentiate opioid analgesia by acting on filamin A, a scaffolding protein involved in μ-opioid receptor signaling. This dose is termed ultra low-dose naltrexone/naloxone (ULDN). It has been of use in postoperative control of analgesia by reducing the need for the total amount of opioids following surgery, as well as ameliorating certain side-effects of opioid-related treatment. A dosing range between 1 μg and 1 mg comprises very low-dose naltrexone (VLDN), which has primarily been used as an experimental adjunct treatment for boosting tolerability of opioid-weaning methadone taper. In general, all of the low-dose features regarding naltrexone and naloxone have been only recently and still scarcely scientifically evaluated. This review aims to present an overview of the current knowledge on these topics and summarize the key findings published in peer-review sources. The existing potential of LDN, VLDN, and ULDN for various areas of biomedicine has still not been thoroughly and comprehensively addressed.

Does co-treatment with ultra-low-dose naloxone and morphine provide better analgesia in renal colic patients?

OBJECTIVE

This study attempted to evaluate the efficacy of ultra-low-dose intravenous (IV) naloxone combined with IV morphine, as compared to IV morphine alone, in terms of reducing pain and morphine-induced side effects in patients with renal colic.

METHODS

In this double-blind clinical trial, 150 patients aged 34 to 60 years old who presented to the emergency department (ED) with renal colic were randomly allocated to either an intervention group that received ultra-low-dose IV naloxone combined with IV morphine or to a control group that received morphine plus a placebo. The severity of pain, sedation, and nausea were assessed and recorded for all patients at entrance to the ED (T1), then at 20 (T2), 40 (T3), 60 (T4), 120 (T5), and 180 (T6) minutes after starting treatment. The Numeric Rating Scale (NRS) was used for the assessment of pain and nausea intensities, and the Ramsay Sedation Scale (RSS) was used to assess sedation.

RESULTS

A GEE model revealed that patients in the naloxone group had non-significantly reduced pain scores compared to those in the morphine group (coefficient = -0.68; 95% CI: -1.24 to -0.11, Wald X2 (1) = 5.41, p = 0.02). The sedation outcome demonstrated no statistically significant differences at T1 to T4 among patients with renal colic compared to the ones who only received morphine. At T5 and T6, 1.5% vs. 20% and 1.5% vs. 16.9% of subjects from the naloxone group versus the morphine group obtained RSS scores equal to 3, respectively (p = 0.001 and p = 0.004, respectively).

CONCLUSIONS

Compared to patients who only received IV morphine, co-treatment of ultra-low-dose naloxone with morphine could not provide better analgesia and sedation/agitation states in renal colic 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.

The effect of naloxone treatment on opioid-induced side effects: A meta-analysis of randomized and controlled trails

BACKGROUND

To evaluate the effects of naloxone on opioid-induced side effects, the present meta-analysis was constructed.

METHODS

Electronic databases including PubMed, EMBASE, and CNKI (China National Knowledge Internet) were used for literature search. Studies on comparison of opioid-side effects between naloxone-treated group and placebo or normal saline-related group were included in the meta-analysis. Heterogeneity analysis was performed with Chi-square and I test. Pooled analysis was based on fixed-effects model, if heterogeneity between the eligible studies was negligible (I < 50%, P > 0.05), otherwise, random-effects model was used. Sensitivity analysis was applied to assess the robustness of the results and publication bias was evaluated by Begg and Egger test.

RESULTS

Thirteen studies including 1138 patients were included in the meta-analysis. Pooled analysis indicated that naloxone could significantly reduce the occurrence of pruritus (RR [risk ratio] = 0.252, 95% CI [confidence interval] = 0.137-0.464), nausea (RR = 0.323, 95% CI = 0.245-0.428), and vomiting (RR = 0.338, 95% CI = 0.192-0.593) which were induced by opioids. However, naloxone did not relieve pain (standardized mean difference [SMD] = -0.052, 95% CI = -0.453 to 0.348) and somnolence (RR = 0.561, 95% CI = 0.287 to 1.097) in patients received opioid treatment. Additionally, there were no significant publication bias between the included studies (Begg test, P = 0.602; Egger test, P = 0.388).

CONCLUSION

Addition of naloxone might act as an effective treatment for prophylaxis of opioid-induced pruritus, nausea, and vomiting in clinical practice.