The P2Y1 receptor in the colonic myenteric plexus of rats and its correlation with opioid-induced constipation.

This study was designed to explore the expression changes of P2Y1 receptors in the distal colonic myenteric layer of rats. An opioid induced constipation(OIC) rat model was generated by intraperitoneal (i.p) injection of loperamide. At 7 days post-treatment, the model rats were assessed by calculating the fecal water content and the gastrointestinal transit ratio. The immunofluorescence (IF)-based histochemical study was used to observe the distribution of P2Y1 receptors in the distal colonic myenteric plexus. Western blotting (WB) was performed to evaluate the expression changes of P2Y1 proteins in the myenteric layer, and the electrophysiological approaches were carried out to determine the regulatory roles of P2Y1 receptors on distal colonic motor function. IF showed that P2Y1 receptors are co-expressed MOR in the enteric nerve cells of the distal colonic myenteric plexus. Moreover, the WB revealed that the protein levels of P2Y1 were significantly decreased in the distal colonic myenteric layer of OIC rats. In vitro tension experiments exhibited that the P2Y1 receptor antagonist MRS2500 enhanced the spontaneous contraction amplitude, adding EM2 and ß-FNA did not have any effect on MRS2500. Therefore, P2Y1 receptor expression could be associated with the occurrence of OIC in this rat model and the regulation of colonic motility by MOR may be related to the release of purine neurotransmitters such as ATP in the colonic nervous system.

Efficacy and safety of naldemedine treatment for opioid-induced constipation in gastrointestinal cancer: a retrospective analysis.

BACKGROUND: Gastrointestinal cancers are one of the most common cancer cases worldwide. Cancer treatment is multidisciplinary, which includes opioid pain management. Opioid analgesics cause opioid-induced constipation (OIC) with the onset of effect. Naldemedine, a peripheral opioid receptor antagonist, is an OIC-modifying agent, but no focused efficacy and safety analysis has been conducted for its use in gastrointestinal cancers. METHODS: We retrospectively evaluated patients with gastrointestinal cancer treated with naldemedine at ten institutions in Japan from June 2017 to August 2019. Patients with gastrointestinal cancer who initiated treatment with opioids during hospitalization and were treated with naldemedine for the first time were included in the study. The gastrointestinal cancer types included were esophageal, gastric, small bowel, and colorectal cancers. We assessed the defecation frequency before and after the initiation of naldemedine use. Responders were defined as patients who defecated three or more times/week, with an increase from the baseline of one or more bowel movements/week over seven days after starting naldemedine. RESULTS: Thirty-three patients were observed for one week before and after starting naldemedine. Twenty-one patients had an increase in defecation frequency of at least three times per week or at least once per week above the baseline. The response rate was 63.6% [95% confidence interval (CI): 46.6-77.9%]. The median number of bowel movements for a week before and after the initiation of naldemedine treatment was 3 (range, 0-13) and 7 (range, 1-39), respectively, in the overall population (n=33), with a significant increase in defecation frequency following naldemedine administration (Wilcoxon signed rank test, P<0.005). Diarrhea was the predominant gastrointestinal symptom, with 13 (39.4%) patients experiencing grade 1 and none experiencing grade 3 or grade 4 adverse events. The frequency of other grade 1 adverse events was low abdominal pain in two patients, nausea in two patients, and anorexia in one patient, without any grade 2-4 adverse events. CONCLUSIONS: The results of the study suggest that naldemedine is effective and safe in clinical practice for gastrointestinal cancer treatment.

Post-marketing surveillance of the safety and effectiveness of naldemedine in the management of opioid-induced constipation in patients with cancer pain in Japan.

PURPOSE: This prospective post-marketing surveillance (PMS) was designed to collect data on the safety and effectiveness of naldemedine in routine clinical practice in patients with opioid-induced constipation (OIC) and cancer pain in Japan and explore the characteristics of patients prone to diarrhea. METHODS: The enrolled patients received naldemedine (0.2 mg, once a day) orally for up to 12 weeks. In the safety analysis, adverse drug reactions (ADRs), including diarrhea as a special interest, were assessed. Effectiveness was evaluated, especially regarding the frequency and condition of bowel movement. RESULTS: In the safety analysis set (n = 1177), 145 ADRs occurred in 133 (11.30%) patients, and diarrhea was the most frequent event (n = 107, 9.09%). Most cases of diarrhea were non-serious (98.1%). Most ADRs were non-serious (93.8%), and they resolved within 2 weeks (75.9%). No patient characteristics influenced the risk of diarrhea development or aggravation. Both the frequency (75.0% and 83.2%) and condition of bowel movement (80.0% and 88.0%) were improved at 2 and 12 weeks, respectively in the effectiveness analysis set (n = 953). Frequency and condition of bowel movement were also improved in patients excluded (e.g., Eastern Cooperative Oncology Group performance status was ≥ 3) or with very small numbers (e.g., received weak opioid) in the clinical trials. CONCLUSIONS: This PMS indicates that naldemedine is well tolerated and effective in patients of various backgrounds in routine clinical practice who have OIC and cancer pain. TRIAL REGISTRATION: UMIN000042851.

Personalizing Cancer Pain Therapy: Insights from the Rational Use of Analgesics (RUA) Group.

INTRODUCTION: A previous Delphi survey from the Rational Use of Analgesics (RUA) project involving Italian palliative care specialists revealed some discrepancies between current guidelines and clinical practice with a lack of consensus on items regarding the use of strong opioids in treating cancer pain. Those results represented the basis for a new Delphi study addressing a better approach to pain treatment in patients with cancer. METHODS: The study consisted of a two-round multidisciplinary Delphi study. Specialists rated their agreement with a set of 17 statements using a 5-point Likert scale (0 = totally disagree and 4 = totally agree). Consensus on a statement was achieved if the median consensus score (MCS) (expressed as value at which at least 50% of participants agreed) was at least 4 and the interquartile range (IQR) was 3-4. RESULTS: This survey included input from 186 palliative care specialists representing all Italian territory. Consensus was reached on seven statements. More than 70% of participants agreed with the use of low dose of strong opioids in moderate pain treatment and valued transdermal route as an effective option when the oral route is not available. There was strong consensus on the importance of knowing opioid pharmacokinetics for therapy personalization and on identifying immediate-release opioids as key for tailoring therapy to patients' needs. Limited agreement was reached on items regarding breakthrough pain and the management of opioid-induced bowel dysfunction. CONCLUSION: These findings may assist clinicians in applying clinical evidence to routine care settings and call for a reappraisal of current pain treatment recommendations with the final aim of optimizing the clinical use of strong opioids in patients with cancer.

Naldemedine-induced Opioid Withdrawal Syndrome in a Patient with Breast Cancer without Brain Metastasis.

Opioid-induced-constipation (OIC) can be treated by naldemedine and other peripherally acting mu-opioid receptor antagonists (PAMORA) via a novel mechanism. We describe the case of a 52-year-old female outpatient who developed OIC while receiving oxycodone for pain due to cancer with multiple bone metastases. Although she did not have brain metastasis, opioid withdrawal syndrome (OWS) developed after taking naldemedine orally. Her Clinical Opiate-Withdrawal Score (COWS) was 19 (moderate symptoms). However, she recovered from OWS on intravenous fentanyl and a continuous infusion of oxycodone. She did not develop OWS thereafter and was discharged two days after recovery.