Randomized, double-blind, placebo-controlled study to investigate the pharmacodynamic interaction of 5-HT3 antagonist ondansetron and paracetamol in postoperative patients operated in an ENT department under local anesthesia

Evaluation of the effect of intraoperative tropisetron on postoperative rebound pain after brachial plexus block: a randomized controlled trial

Introduction

Postoperative rebound pain after peripheral nerve block increases patient suffering and delays recovery after surgery.

Objectives

We tested whether the 5HT-3 receptor antagonist and α7nAChR agonist tropisetron could prevent postoperative rebound pain.

Methods

A total of 115 patients were randomized to receive 5-mg/5-mL tropisetron or the same volume of normal saline. Pain intensity was measured with the numerical rating scale of pain (NRS). Rebound pain was defined as a change from mild pain (NRS ≤ 3) measured in the postanesthesia care unit to severe pain (NRS ≥ 7) within 24 hours after peripheral nerve blockade. Logistic regression was used to identify relevant factors associated with postoperative rebound pain.

Results

Tropisetron did not affect the NRS score or the incidence of rebound pain after peripheral nerve block. Logistic regression revealed that preoperative pain, bone surgery, and length of incision were risk factors for postoperative rebound pain, and patient-controlled analgesia was protective against postoperative rebound pain.

Conclusion

Tropisetron does not affect the incidence of rebound pain after peripheral nerve block. Patients at high risk of postoperative rebound pain should be identified for appropriate management. Registration site: www.chictr.org.cn (ChiCTR2300069994).

Paracetamol-Induced Hypothermia in Rodents: A Review on Pharmacodynamics

Paracetamol can induce hypothermia in humans and rodents. The study’s aim is to review the mechanisms of paracetamol-induced hypothermia in rodents or the results issued from in vitro studies on the same species’ tissues (in doses that do not produce hepatic impairment) using the latest developments published in scientific journals over the last 15 years. Available human studies are also analysed. An extensive search in PubMed databases exploring the hypothermic response to paracetamol was conducted. 4669 articles about paracetamol’s effects on body temperature in mice or rats were found. After applying additional filters, 20 articles were selected for review, with 9 of them presented in tabular forms. The analysis of these articles found that the hypothermic effect of paracetamol is due to the inhibition of a cyclooxygenase-1 variant, is potentiated by endothelin receptor antagonists, and can be mediated through GABAA receptors and possibly through transient receptor potential cation channel subfamily A member 1 via N-acetyl-p-benzoquinone imine in the central nervous system. Human studies confirm the in vivo and in vitro experiments in rodents regarding the presence of a hypothermic effect after high, non-toxic doses of paracetamol. Further research is required to understand the mechanisms behind paracetamol’s hypothermic effect in humans.

Paracetamol versus Paracetamol Plus Ondansetron on Acute Postoperative Pain

This study was performed to determine the comparative efficacy of paracetamol alone versus paracetamol plus ondansetron on acute postoperative pain after abdominal surgeries in Azad University hospitals in 2017 and 2019. In this randomized clinical trial, 62 consecutive patients under abdominal surgeries, were randomly divided into two groups, group 1 patient who received paracetamol alone 1 gram and group 2 patient who received paracetamol 1 gram plus 4 mg ondansetron and the pain severities were determined and compared between groups at recovery and after 4 and 24 hours. The results of this study revealed that there were no statistically significant differences between two groups for the postoperative pain severity and analgesic use ( p > 0.05). It may be concluded that addition of ondansetron to paracetamol would not result in further postoperative pain reduction and additive use of this drug is not recommended.

Transmission pathways and mediators as the basis for clinical pharmacology of pain

INTRODUCTION

Mediators in pain transmission are the targets of a multitude of different analgesic pharmaceuticals. This review explores the most significant mediators of pain transmission as well as the pharmaceuticals that act on them. Areas covered: The review explores many of the key mediators of pain transmission. In doing so, this review uncovers important areas for further research. It also highlights agents with potential for producing novel analgesics, probes important interactions between pain transmission pathways that could contribute to synergistic analgesia, and emphasizes transmission factors that participate in transforming acute injury into chronic pain. Expert commentary: This review examines current pain research, particularly in the context of identifying novel analgesics, highlighting interactions between analgesic transmission pathways, and discussing factors that may contribute to the development of chronic pain after an acute injury.

Comparative Pre-Emptive Analgesic Efficacy Study of Novel Antiepileptic Agents Lamotrigine and Topiramate in Patients Undergoing Major Surgeries at a Tertiary Care Hospital: A Randomized Double Blind Clinical Trial

BACKGROUND

Central nervous sensitization, following surgical injury, leads to postoperative pain hypersensitivity due to lowered pain threshold in peripheral nociceptors and increased excitability of spinal neurons. Pre-emptive analgesia is intended to decrease pain perception and overall analgesic need by use of drug regimen, seizing CNS sensitization before exposure to painful stimuli. Few studies support pre-emptive analgesic efficacy of novel antiepileptic agent Gabapentin. Though Topiramate and Lamotrigine have been proven analgesic in animal models of chronic pain and clinical studies of Gabapentin-resistant neuropathic pain, literature search revealed scarce data on its pre-emptive analgesic efficacy.

PURPOSE

This study is designed to study and compare the pre-emptive analgesic efficacy of Lamotrigine, Topiramate, and Diclofenac sodium in postoperative pain control.

METHODS

This randomized clinical trial included 90 patients of either sex, between 18 and 70 years undergoing major surgeries. Patients were randomly allocated to control and test groups and received respective treatment 30 min before induction of anesthesia. Aldrete's and pain scores were recorded using the Visual Analog Scale, Facial and Behavioral Rating Scale at awakening and at 1, 2, 4, 6, and 24 h. Postoperative rescue analgesic consumption for 24 h was recorded.

RESULTS

Significantly higher pain scores were observed in the Topiramate group postoperatively for 2 h on all pain scales (p < 0.05), whereas in the control group it was significantly higher at 1 h (p < 0.05). Lamotrigine-treated patients were more comfortable throughout the study with significantly less (p < 0.05) postoperative analgesic requirement.

CONCLUSIONS

Study results strongly suggest the pre-emptive analgesic efficacy of a single oral dose of Lamotrigine over Diclofenac and Topiramate in postoperative pain control.

A Randomized Double-Blind Placebo-Controlled Study to Compare Preemptive Analgesic Efficacy of Novel Antiepileptic Agent Lamotrigine in Patients Undergoing Major Surgeries

BACKGROUND

If postoperative acute pain remains unrelieved, it may result in significant morbidity and mortality. Preemptive analgesic initiated before surgery offers premature analgesia even before exposure to an initial noxious stimulus bestowing effective postoperative analgesia. In developed countries, it is regularly practiced as a part of well-defined protocol. In our country however, only a few centers practice it and that too irregularly and with undefined protocol. Few studies support preemptive analgesic efficacy of novel antiepileptic agent gabapentin. Though lamotrigine is a proven analgesic in animal models of chronic pain and clinical studies of gabapentin-resistant neuropathic pain, a literature search revealed scarce data on its preemptive analgesic efficacy.

AIMS

The present study is designed to study the preemptive analgesic efficacy of lamotrigine in comparison with diclofenac sodium in postoperative pain control.

MATERIALS AND METHODS

This randomized clinical trial included 90 patients of both sexes, between 18 years and 70 years undergoing major surgeries. Patients were randomly allocated into placebo, control, and test groups and received the respective treatment 30 min before the induction of anesthesia. Aldrete score and pain score were recorded using visual analog scale (VAS), facial rating scale (FRS), and behavioral rating scale (BRS) at awakening and at 1 h, 2 h, 4 h, 6 h, and 24 h. Postoperative rescue analgesic consumption for 24 h was recorded.

RESULTS

Significantly higher pain scores were observed in the placebo group postoperatively for 2 h on all pain scales (P < 0.05), whereas in the control group it was significantly higher at 1 h (P < 0.05). The test group patients were more comfortable throughout the study and postoperative analgesic requirement was significantly less (P < 0.05).

CONCLUSIONS

The study recommends the use of single oral dose lamotrigine as preemptive analgesic for effective postoperative pain control.

Repeated tender point injections of granisetron alleviate chronic myofascial pain--a randomized, controlled, double-blinded trial

Background

Serotonin (5-HT) mediates pain by peripheral 5-HT₃-receptors. Results from a few studies indicate that intramuscular injections of 5-HT₃-antagonists may reduce musculoskeletal pain. The aim of this study was to investigate if repeated intramuscular tender-point injections of the 5-HT₃-antagonist granisetron alleviate pain in patients with myofascial temporomandibular disorders (M-TMD).

Methods

This prospective, randomized, controlled, double blind, parallel-arm trial (RCT) was carried out during at two centers in Stockholm, Sweden. The randomization was performed by a researcher who did not participate in data collection with an internet-based application (www.randomization.com). 40 patients with a diagnose of M-TMD according to the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) were randomized to receive repeated injections, one week apart, with either granisetron (GRA; 3 mg) or isotonic saline as control (CTR).

Results

The median weekly pain intensities decreased significantly at all follow-ups (1-, 2-, 6-months) in the GRA-group (Friedman test; P < 0.05), but not in the CTR-group (Friedman-test; P > 0.075). The numbers needed to treat (NNT) were 4 at the 1- and 6-month follow-ups, and 3.3 at the 2-month follow-up in favor of granisetron.

Conclusions

Repeated intramuscular tender-point injections with granisetron provide a new pharmacological treatment possibility for myofascial pain patients with repeated intramuscular tender-point injections with the serotonin type 3 antagonist granisetron. It showed a clinically relevant pain reducing effect in the temporomandibular region, both in a short- and long-term aspect.

Trial registration

European Clinical Trials Database 2005-006042-41 as well as at Clinical Trials NCT02230371.