Antagonistic Effects of Ondansetron and Tramadol? A Randomized Placebo and Active Drug Controlled Study

The Effect of Ondansetron on the Analgesic Efficacy of Tramadol in Patients Undergoing Laparoscopic Cholecystectomy

Purpose

Investigating the effect of ondansetron on the efficacy of tramadol in patients undergoing laparoscopic cholecystectomy.

Methods

Sixty American Society of Anesthesiologists (ASA) I-II patients over the age of 18 who underwent laparoscopic cholecystectomy were included in this study. All patients were given 1 mg/kg tramadol intravenously (iv) during the intraoperative period. Patients were randomly assigned to receive either 4 mg ondansetron (Group O) or 2 mL saline (Group S). Postoperative tramadol consumption, pain score (NRS), intensity of nausea (NRS), presence of vomiting, consumption of rescue analgesics and antiemetics, and patient satisfaction were recorded.

Results

A total of 60 patients were enrolled in the study; five patients were excluded due to deviation from the protocol. Data from 55 patients (Group O: 28 patients, Group S: 27 patients) were evaluated in the study. No differences between the two groups were detected for postoperative consumption of tramadol, pain score (NRS), intensity of nausea (NRS), presence of vomiting, consumption of rescue analgesics and antiemetics, and patient satisfaction.

Conclusions

The results showed that coadministration of tramadol and ondansetron did not change tramadol consumption during the postoperative 24 hours after laparoscopic cholecystectomy. Clinical trial registration number is as follows: https://clinicaltrials.gov/ct2/show/NCT04745273-01/31/2021.

Drugs for preventing postoperative nausea and vomiting in adults after general anaesthesia: a network meta-analysis

BACKGROUND

Postoperative nausea and vomiting (PONV) is a common adverse effect of anaesthesia and surgery. Up to 80% of patients may be affected. These outcomes are a major cause of patient dissatisfaction and may lead to prolonged hospital stay and higher costs of care along with more severe complications. Many antiemetic drugs are available for prophylaxis. They have various mechanisms of action and side effects, but there is still uncertainty about which drugs are most effective with the fewest side effects.

OBJECTIVES

• To compare the efficacy and safety of different prophylactic pharmacologic interventions (antiemetic drugs) against no treatment, against placebo, or against each other (as monotherapy or combination prophylaxis) for prevention of postoperative nausea and vomiting in adults undergoing any type of surgery under general anaesthesia • To generate a clinically useful ranking of antiemetic drugs (monotherapy and combination prophylaxis) based on efficacy and safety • To identify the best dose or dose range of antiemetic drugs in terms of efficacy and safety SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, the Cumulative Index to Nursing and Allied Health Literature (CINAHL), the World Health Organization International Clinical Trials Registry Platform (WHO ICTRP), ClinicalTrials.gov, and reference lists of relevant systematic reviews. The first search was performed in November 2017 and was updated in April 2020. In the update of the search, 39 eligible studies were found that were not included in the analysis (listed as awaiting classification).

SELECTION CRITERIA

Randomized controlled trials (RCTs) comparing effectiveness or side effects of single antiemetic drugs in any dose or combination against each other or against an inactive control in adults undergoing any type of surgery under general anaesthesia. All antiemetic drugs belonged to one of the following substance classes: 5-HT₃ receptor antagonists, D₂ receptor antagonists, NK₁ receptor antagonists, corticosteroids, antihistamines, and anticholinergics. No language restrictions were applied. Abstract publications were excluded.

DATA COLLECTION AND ANALYSIS

A review team of 11 authors independently assessed trials for inclusion and risk of bias and subsequently extracted data. We performed pair-wise meta-analyses for drugs of direct interest (amisulpride, aprepitant, casopitant, dexamethasone, dimenhydrinate, dolasetron, droperidol, fosaprepitant, granisetron, haloperidol, meclizine, methylprednisolone, metoclopramide, ondansetron, palonosetron, perphenazine, promethazine, ramosetron, rolapitant, scopolamine, and tropisetron) compared to placebo (inactive control). We performed network meta-analyses (NMAs) to estimate the relative effects and ranking (with placebo as reference) of all available single drugs and combinations. Primary outcomes were vomiting within 24 hours postoperatively, serious adverse events (SAEs), and any adverse event (AE). Secondary outcomes were drug class-specific side effects (e.g. headache), mortality, early and late vomiting, nausea, and complete response. We performed subgroup network meta-analysis with dose of drugs as a moderator variable using dose ranges based on previous consensus recommendations. We assessed certainty of evidence of NMA treatment effects for all primary outcomes and drug class-specific side effects according to GRADE (CINeMA, Confidence in Network Meta-Analysis). We restricted GRADE assessment to single drugs of direct interest compared to placebo.

MAIN RESULTS

We included 585 studies (97,516 randomized participants). Most of these studies were small (median sample size of 100); they were published between 1965 and 2017 and were primarily conducted in Asia (51%), Europe (25%), and North America (16%). Mean age of the overall population was 42 years. Most participants were women (83%), had American Society of Anesthesiologists (ASA) physical status I and II (70%), received perioperative opioids (88%), and underwent gynaecologic (32%) or gastrointestinal surgery (19%) under general anaesthesia using volatile anaesthetics (88%). In this review, 44 single drugs and 51 drug combinations were compared. Most studies investigated only single drugs (72%) and included an inactive control arm (66%). The three most investigated single drugs in this review were ondansetron (246 studies), dexamethasone (120 studies), and droperidol (97 studies). Almost all studies (89%) reported at least one efficacy outcome relevant for this review. However, only 56% reported at least one relevant safety outcome. Altogether, 157 studies (27%) were assessed as having overall low risk of bias, 101 studies (17%) overall high risk of bias, and 327 studies (56%) overall unclear risk of bias. Vomiting within 24 hours postoperatively Relative effects from NMA for vomiting within 24 hours (282 RCTs, 50,812 participants, 28 single drugs, and 36 drug combinations) suggest that 29 out of 36 drug combinations and 10 out of 28 single drugs showed a clinically important benefit (defined as the upper end of the 95% confidence interval (CI) below a risk ratio (RR) of 0.8) compared to placebo. Combinations of drugs were generally more effective than single drugs in preventing vomiting. However, single NK₁ receptor antagonists showed treatment effects similar to most of the drug combinations. High-certainty evidence suggests that the following single drugs reduce vomiting (ordered by decreasing efficacy): aprepitant (RR 0.26, 95% CI 0.18 to 0.38, high certainty, rank 3/28 of single drugs); ramosetron (RR 0.44, 95% CI 0.32 to 0.59, high certainty, rank 5/28); granisetron (RR 0.45, 95% CI 0.38 to 0.54, high certainty, rank 6/28); dexamethasone (RR 0.51, 95% CI 0.44 to 0.57, high certainty, rank 8/28); and ondansetron (RR 0.55, 95% CI 0.51 to 0.60, high certainty, rank 13/28). Moderate-certainty evidence suggests that the following single drugs probably reduce vomiting: fosaprepitant (RR 0.06, 95% CI 0.02 to 0.21, moderate certainty, rank 1/28) and droperidol (RR 0.61, 95% CI 0.54 to 0.69, moderate certainty, rank 20/28). Recommended and high doses of granisetron, dexamethasone, ondansetron, and droperidol showed clinically important benefit, but low doses showed no clinically important benefit. Aprepitant was used mainly at high doses, ramosetron at recommended doses, and fosaprepitant at doses of 150 mg (with no dose recommendation available). Frequency of SAEs Twenty-eight RCTs were included in the NMA for SAEs (10,766 participants, 13 single drugs, and eight drug combinations). The certainty of evidence for SAEs when using one of the best and most reliable anti-vomiting drugs (aprepitant, ramosetron, granisetron, dexamethasone, ondansetron, and droperidol compared to placebo) ranged from very low to low. Droperidol (RR 0.88, 95% CI 0.08 to 9.71, low certainty, rank 6/13) may reduce SAEs. We are uncertain about the effects of aprepitant (RR 1.39, 95% CI 0.26 to 7.36, very low certainty, rank 11/13), ramosetron (RR 0.89, 95% CI 0.05 to 15.74, very low certainty, rank 7/13), granisetron (RR 1.21, 95% CI 0.11 to 13.15, very low certainty, rank 10/13), dexamethasone (RR 1.16, 95% CI 0.28 to 4.85, very low certainty, rank 9/13), and ondansetron (RR 1.62, 95% CI 0.32 to 8.10, very low certainty, rank 12/13). No studies reporting SAEs were available for fosaprepitant. Frequency of any AE Sixty-one RCTs were included in the NMA for any AE (19,423 participants, 15 single drugs, and 11 drug combinations). The certainty of evidence for any AE when using one of the best and most reliable anti-vomiting drugs (aprepitant, ramosetron, granisetron, dexamethasone, ondansetron, and droperidol compared to placebo) ranged from very low to moderate. Granisetron (RR 0.92, 95% CI 0.80 to 1.05, moderate certainty, rank 7/15) probably has no or little effect on any AE. Dexamethasone (RR 0.77, 95% CI 0.55 to 1.08, low certainty, rank 2/15) and droperidol (RR 0.89, 95% CI 0.81 to 0.98, low certainty, rank 6/15) may reduce any AE. Ondansetron (RR 0.95, 95% CI 0.88 to 1.01, low certainty, rank 9/15) may have little or no effect on any AE. We are uncertain about the effects of aprepitant (RR 0.87, 95% CI 0.78 to 0.97, very low certainty, rank 3/15) and ramosetron (RR 1.00, 95% CI 0.65 to 1.54, very low certainty, rank 11/15) on any AE. No studies reporting any AE were available for fosaprepitant. Class-specific side effects For class-specific side effects (headache, constipation, wound infection, extrapyramidal symptoms, sedation, arrhythmia, and QT prolongation) of relevant substances, the certainty of evidence for the best and most reliable anti-vomiting drugs mostly ranged from very low to low. Exceptions were that ondansetron probably increases headache (RR 1.16, 95% CI 1.06 to 1.28, moderate certainty, rank 18/23) and probably reduces sedation (RR 0.87, 95% CI 0.79 to 0.96, moderate certainty, rank 5/24) compared to placebo. The latter effect is limited to recommended and high doses of ondansetron. Droperidol probably reduces headache (RR 0.76, 95% CI 0.67 to 0.86, moderate certainty, rank 5/23) compared to placebo. We have high-certainty evidence that dexamethasone (RR 1.00, 95% CI 0.91 to 1.09, high certainty, rank 16/24) has no effect on sedation compared to placebo. No studies assessed substance class-specific side effects for fosaprepitant. Direction and magnitude of network effect estimates together with level of evidence certainty are graphically summarized for all pre-defined GRADE-relevant outcomes and all drugs of direct interest compared to placebo in http://doi.org/10.5281/zenodo.4066353.

AUTHORS' CONCLUSIONS

We found high-certainty evidence that five single drugs (aprepitant, ramosetron, granisetron, dexamethasone, and ondansetron) reduce vomiting, and moderate-certainty evidence that two other single drugs (fosaprepitant and droperidol) probably reduce vomiting, compared to placebo. Four of the six substance classes (5-HT₃ receptor antagonists, D₂ receptor antagonists, NK₁ receptor antagonists, and corticosteroids) were thus represented by at least one drug with important benefit for prevention of vomiting. Combinations of drugs were generally more effective than the corresponding single drugs in preventing vomiting. NK₁ receptor antagonists were the most effective drug class and had comparable efficacy to most of the drug combinations. 5-HT₃ receptor antagonists were the best studied substance class. For most of the single drugs of direct interest, we found only very low to low certainty evidence for safety outcomes such as occurrence of SAEs, any AE, and substance class-specific side effects. Recommended and high doses of granisetron, dexamethasone, ondansetron, and droperidol were more effective than low doses for prevention of vomiting. Dose dependency of side effects was rarely found due to the limited number of studies, except for the less sedating effect of recommended and high doses of ondansetron. The results of the review are transferable mainly to patients at higher risk of nausea and vomiting (i.e. healthy women undergoing inhalational anaesthesia and receiving perioperative opioids). Overall study quality was limited, but certainty assessments of effect estimates consider this limitation. No further efficacy studies are needed as there is evidence of moderate to high certainty for seven single drugs with relevant benefit for prevention of vomiting. However, additional studies are needed to investigate potential side effects of these drugs and to examine higher-risk patient populations (e.g. individuals with diabetes and heart disease).

From Tramadol to Methadone: Opioids in the Treatment of Pain and Dyspnea in Pediatric Palliative Care

BACKGROUND

More than 15,000 children die annually in the United States due to an underlying life-limiting disease and the majority of those children experience distressing symptoms, which are not adequately relieved, such as pain and dyspnea. Multimodal analgesia, that is multiple agents, interventions, rehabilitation, psychological modalities, and integrative (nonpharmacologic) therapies, act synergistically for more effective pediatric pain and symptom control with fewer side effects than a single analgesic or modality. However, opioids, such as morphine, fentanyl, hydromorphone, oxycodone, and methadone (in the United Kingdom: diamorphine) remain the mainstay medication to effectively treat pain and dyspnea in children with serious illness.

METHODS

This article reviews commonly used opioids in Pediatric Palliative Care, which a special emphasis on 2 potentially particularly effective multimechanistic opioids: tramadol and methadone.

RESULTS

Methadone, due to its multimechanistic action profile, is possibly among the most effective and most underutilized opioid analgesics in children with severe unrelieved pain at end of life. However, methadone should not be prescribed by those unfamiliar with its use: Its effects should be closely monitored for several days, particularly when it is first started and after any dose changes.

CONCLUSIONS

Tramadol appears to play a key role in treating episodes of inconsolability in children with progressive neurologic, metabolic, or chromosomally based condition with impairment of the central nervous system. However, the recent 2017 United States Food and Drug Administration (FDA) warning against pediatric use of tramadol does not seem to be based on clinical evidence, and therefore puts children at risk for unrelieved pain or increased respiratory depression.

Ramosetron Does Not Reduce the Analgesic Efficacy of Tramadol after Gynecological Laparoscopic Surgery

Background

The effect of ramosetron on the analgesic action of tramadol is not well known when ramosetron is added to intravenous-tramadol patient-controlled analgesia (PCA) and infused continuously. The aim of this randomized noninferiority study was to evaluate the effects of ramosetron on the analgesic action of tramadol when it is administered simultaneously in women undergoing laparoscopic gynecology who are receiving tramadol via IV PCA.

Method

This study used a prospective, randomized, controlled, noninferiority clinical trial design and compared the analgesic effect of tramadol plus ramosetron with that of tramadol only. A total of 110 postoperative patients, who were using IV PCA tramadol, were randomly assigned either to a group receiving ramosetron (group R, n=49) or to a group that received the same volume of normal saline continuously (group N, n=51). Observation time points for cumulative tramadol consumption were the first hour, and every 4 h up to 12 h and then 24 h after surgery. Pain intensity at rest and during movement, coughing, and nausea scores, the analgesic and antiemetic doses used, side effects, and patient satisfaction were evaluated 1 and 24 h after surgery.

Results

Groups R and N received, respectively, 88 ± 55 vs. 79 ± 42 mg tramadol (P=0.511) after 1 h, 211 ± 122 vs. 198 ± 109 mg cumulative tramadol (P=0.610) after 4 h, 244 ± 150 vs. 231 ± 134 mg cumulative tramadol (P= 0.793) after 8 h, 250 ± 156 vs. 247 ± 153 mg cumulative tramadol (P=0.972) after 12 h, and 294 ± 190 vs. 284 ± 178 mg cumulative tramadol (P=0.791) after 24 h, postsurgery. Tramadol plus ramosetron was shown to be not significantly inferior to tramadol alone in alleviating the postoperative pain.

Conclusions

The analgesic effect of tramadol combined with ramosetron was found to be noninferior to tramadol alone for postoperative PCA after laparoscopic gynecologic surgery.

Efficacy of Tramadol for Pain Management in Patients Receiving Strong Cytochrome P450 2D6 Inhibitors

STUDY OBJECTIVE

Tramadol is metabolized by cytochrome P450 (CYP) 2D6 to form an active metabolite that exhibits its analgesic effect. Medications that inhibit this enzyme are used often in practice, yet the clinical impact of this interaction on the analgesic effects of tramadol has yet to be fully described. The objective was to determine whether a clinically relevant decrease in pain control is observed in patients taking scheduled tramadol concomitantly with a strong CYP2D6 inhibitor.

DESIGN

Retrospective cohort study.

SETTING

Large health care system.

PATIENTS

One hundred fifty-two adult inpatients who received scheduled tramadol for at least 24 hours with (76 patients) or without (76 patients) a strong CYP2D6 inhibitor between January 1, 2012, and February 28, 2017, were included in the analysis. Patients hospitalized for opioid use disorder or those receiving substandard dosing of tramadol were excluded.

MEASUREMENTS AND MAIN RESULTS

The primary outcome was mean breakthrough opiate consumption in the presence and absence of CYP2D6 inhibitors. Secondary outcomes included mean pain scores, length of hospital stay, tramadol discontinuation rates, and prespecified subgroup analyses based on patient sex, race, and specific CYP2D6 inhibitor administered. Patients receiving concurrent CYP2D6 inhibitors required significantly more breakthrough morphine milligram equivalents per day compared with patients receiving scheduled tramadol without CYP2D6 inhibitors (geometric mean ± SD 18.2 ± 6.3 vs 5.7 ± 6.7 mg morphine milligram equivalents, p<0.001). No significant differences existed between cohorts for mean pain score, length of hospital stay, or tramadol discontinuation rate.

CONCLUSION

This study demonstrated a clinically relevant decrease in the efficacy of tramadol when used for pain control in patients receiving a strong CYP2D6 inhibitor. These results should encourage clinicians to review medication lists for this interaction and adjust regimens accordingly to ensure adequate pain control.

Comparision of Analgesic Efficacy of Tramadol Infusion Versus Tramadol Plus Ondansetron Infusion In Medical Intensive Care Unit

Background:

Tramadol, a preferred analgesic due to its less respiratory depression. It also has a central action that blocks the reuptake and enhances the release of serotonin at spinal antinociceptive pathways. Ondansetron, an antiemetic is a serotonin receptor antagonist. Due to the contradictory actions of the two drugs, co-administration of these drugs resulted in higher usage of tramadol. All these studies were done in the postoperative period.

Aim:

The aim of this study is to evaluate the analgesic efficacy of tramadol infusion versus tramadol plus ondansetron infusion in Medical Intensive Care Unit (ICU) patients.

Materials and Methods:

After Institutional Ethical Committee approval, 50 patients who experience pain other than postoperative pain were enrolled and randomized into two groups. Both the groups initially received 50 mg of tramadol intravenously over 10 min followed by Group T+O received 10 mg/h tramadol + 0.4 mg/h ondansetron as an infusion. Group T received 10 mg/h tramadol as infusion. Hemodynamic parameters along with pain assessment using Verbal Rating Scale (VRS) were analyzed at 0, 3, 6, 12, and 24 h. Rescue analgesia was administered if VRS >4. Side effects were noted by condition scoring criteria (CSC) scale.

Results:

Rescue analgesia was administered at 3 h, for three patients in T+O Group and 1 patient in T Group, but this is not statistically significant (P = 0.153). No rescue analgesia was required in both the groups at any other point of time. There was fall in heart rate, systolic and diastolic blood pressures, respiratory rate at 0, 3, 6, 12, and 24 h in both the groups but not statistically significant. Grade 1 sedation of CSC scale was observed in two patients of Group T+O and one patient in Group T but not statistically significant (P = 0.153). No nausea and vomiting were seen.

Conclusions:

We conclude that co-administration of tramadol and ondansetron can be practiced in medical ICU patients without any higher requirement in dosage of tramadol.

Comparative Pharmacology and Guide to the Use of the Serotonin 5-HT3 Receptor Antagonists for Postoperative Nausea and Vomiting

Since the introduction of the serotonin 5-hydroxy tryptamine 3 (5-HT₃) receptor antagonists in the early 1990s, the incidence of postoperative nausea and vomiting (PONV) and post-discharge nausea and vomiting (PDNV) has decreased, yet continues to be a problem for the surgical patient. The clinical application of the 5-HT₃ receptor antagonists has helped define the approach and role of these antiemetics in the prevention and treatment of PONV and PDNV. Pharmacological and clinical differences exist among these medications resulting in corresponding differences in effectiveness, safety, optimal dosage, time of administration, and use as combination and rescue antiemetic therapy. The clinical application of the 5-HT₃ receptor antagonist antiemetics has improved the prevention and treatment of PONV and PDNV. The most recent consensus guidelines for PONV published in 2014 outline the use of these antiemetics. The 5-HT₃ receptor antagonists play an important role to help prevent PONV and PDNV in perioperative care pathways such as Enhanced Recovery After Surgery (ERAS). Comparisons and guidelines for use of the 5-HT₃ receptor antagonists in relation to the risk for PONV and PDNV are reviewed.

Role of CYP2D6 Polymorphisms in the Outcome of Postoperative Pain Treatment

OBJECTIVE

To investigate the role of CYP2D6 phenotype in the outcome of postoperative (PO) pain (POP) treatment.

DESIGN

Longitudinal cohort study. Open-label trial with post hoc analysis.

SETTING

General Hospital Surgery and Recovery Units.

PATIENTS

Ninety unrelated Caucasians submitted to abdominal/thoracic surgery.

INTERVENTIONS

Standard multimodal POP treatment including opioids (tramadol) and nonsteroidal anti-inflammatory drugs (ketoprofen) at different dosages and infusion rates according to the predicted mild, moderate, or severe POP.

OUTCOME MEASURES

Pain (Numeric Rating Scale-NRS) and sedation (Ramsay Sedation Scale-RSS) up to 24 hours after surgery. By genotyping 16 CYP2D6 alleles, the four CYP2D6 phenotypes poor metabolizer (PM), intermediate metabolizers (IM), extensive metabolizers (EM) and ultrarapid metabolizers (UM) were predicted.

RESULTS

As compared with the CYP2D6-EM phenotype, in the early PO time (30 min) a higher RSS mean score in IM was observed (P = 0.035). A suggestion towards higher mean score in PM (P = 0.091) and a minor mean score in UM (P = 0.091) was also detected. No difference in the outcome of pain across the CYP2D6 phenotypes was observed.

CONCLUSIONS

In respect to the normal CYP2D6 phenotype, our results suggested that slowly metabolizers (IMs and PMs) might have a major sedation, whereas more rapid metabolizers (UM) a minor sedation, in the early time after surgery. A minor role of CYP2D6 phenotype in PO analgesia may be suggested.

The effect of ondansetron on the efficacy of postoperative tramadol: a systematic review and meta-analysis of a drug interaction

Several studies have investigated the presence of a drug interaction between tramadol and ondansetron that reduced the efficacy of tramadol postoperatively. Most of these studies were small and the results inconsistent, so we performed a systematic review and meta-analysis of randomised controlled trials comparing the cumulative dose of tramadol administered by patient-controlled analgesia within the first 24 h after surgery between subjects receiving tramadol alone and those who received tramadol with ondansetron. Six studies, with a total of 340 participants, met the selection criteria and were included in the meta-analysis. There was an increased tramadol requirement in patients receiving ondansetron. The standardised mean difference in tramadol requirements, expressed in terms of standard deviations (95% CI), was 1.03 (0.54-1.53) (p < 0.001) at 4 h, 0.66 (0.06-1.25) (p = 0.03) at 8 h, 0.86 (0.41-1.31) (p < 0.001) at 12 h and 0.45 (0.01-0.90) (p = 0.046) at 24 h postoperatively, where the mean pooled standard deviations were 79.5, 157.7, 238.1 and 289.4 mg at 4, 8, 12 and 24 h, respectively. There was a significant linear time effect over the 24 h, indicating that the effect of ondansetron on tramadol consumption diminished with time. The results support the presence of a drug interaction between tramadol and ondansetron in the early postoperative period that potentially decreases the effectiveness of tramadol.

Ondansetron: a review of pharmacokinetics and clinical experience in postoperative nausea and vomiting

INTRODUCTION

Postoperative nausea and vomiting (PONV) is associated with poor patient satisfaction and delayed recovery after general anesthesia. Multiple neurotransmitters are involved in the mediation of PONV but despite the introduction of new antiemetics, no completely effective drug exists for its prevention or treatment.

AREAS COVERED

This review provides a detailed description of ondansetron's chemistry, pharmacokinetics, pharmacodynamics, toxicity and a brief review of clinical trials involving ondansetron and the management of PONV. We searched reviews, meta-analysis and randomized controlled trials (Medline, Embase and article reference lists).

EXPERT OPINION

According to current literature, administering ondansetron 4 mg i.v. near the end of surgery provides sufficient protection against PONV in low- and moderate-risk patients, comparable to traditional antiemetics such as antihistamines and droperidol. High-risk patients require a multimodal approach since one quarter of them will not respond to monotherapy. In the future, transdermal formulation or formulations for nasal or buccal delivery will be available. The development of non-racemic mixture consisting of R-ondansetron would enhance the safety profile and probably the efficacy too.

Tramadol Extended-Release for the Management of Pain due to Osteoarthritis

Current knowledge on pathogenesis of osteoarticular pain, as well as the consequent several, especially on the gastrointestinal, renal, and cardiovascular systems, side effects of NSAIDs, makes it difficult to perform an optimal management of this mixed typology of pain. This is especially observable in elderly patients, the most frequently affected by osteoarthritis (OA). Tramadol is an analgesic drug, the action of which has a twofold action. It has a weak affinity to mu opioid receptors and, at the same time, can result in inhibition of the reuptake of noradrenaline and serotonin in nociceptorial descending inhibitory control system. These two mechanisms, "opioidergic" and "nonopioidergic," are the grounds for contrasting certain types of pain that are generally less responsive to opioids, such as neuropathic pain or mixed OA pain. The extended-release formulation of tramadol has good efficacy and tolerability and acts through a dosing schedule that allows a high level of patients compliance to therapies with a good recovery outcome for the patients' functional status.

Systemic metoclopramide to prevent postoperative nausea and vomiting: a meta-analysis without Fujii's studies

Previous evidence suggested that 10 mg systemic metoclopramide is not effective to prevent postoperative nausea and/or vomiting (PONV) in patients receiving general anaesthesia. However, the evidence included data with questioned validity by the author Yoshitaka Fujii. The objective of the current study was to examine the effect of a systemic dose of 10 mg metoclopramide to prevent PONV. This quantitative systematic review was performed according to the PRISMA guidelines. A wide search was performed to identify randomized clinical trials that evaluated systemic 10 mg metoclopramide as a prophylactic agent to reduce PONV. Meta-analysis was performed using a random-effect model. Thirty trials evaluating the effect of 10 mg systemic metoclopramide in 3328 subjects on PONV outcomes were included. Metoclopramide reduced the incidence of 24 h PONV compared with control, odds ratio (OR) [95% confidence interval (CI)] of 0.58 (0.43-0.78), number needed to treat (NNT)=7.8. When evaluated as separate outcomes, metoclopramide also decreased the incidence of nausea over 24 h, OR (95% CI) of 0.51 (0.38-0.68), NNT=7.1, and vomiting over 24 h, OR (95% CI) of 0.51 (0.40-0.66), NNT=8.3. A post hoc analysis examining three studies with questioned validity performed by the author Yoshitaka Fujii that would meet criteria for inclusion in the current study did not demonstrate a significant benefit of metoclopramide compared with control on the incidence of 24 h PONV. Our findings suggest that metoclopramide 10 mg i.v. is effective to prevent PONV in patients having surgical procedures under general anaesthesia. Metoclopramide seems to be a reasonable agent to prevent PONV.

Involvement of mast cells in a mouse model of postoperative pain

Recent studies have indicated that nearly half of all surgical patients still have inadequate pain relief; therefore, it is becoming increasingly more important to understand the mechanisms involved in postoperative pain in order to be better treated. Previous studies have shown that incisions can cause mast cell degranulation. Thus, the aim of this study was to investigate the involvement of mast cells in a model of postoperative pain in mice. The depletion of mast cell mediators produced by pre-treatment with compound 48/80 (intraplantar (i.pl.)) widely (98 ± 23% of inhibition) and extensively (up to 96 h) prevented postoperative nociception and reduced histamine and serotonin levels (88 ± 4% and 68 ± 10%, respectively) in operated tissue. Furthermore, plantar surgery produced immense mast cell degranulation, as assessed by histology and confirmed by the increased levels of serotonin (three-fold higher) and histamine (fifteen-fold higher) in the perfused tissue, 1h after surgery. Accordingly, pre-treatment with the mast cell membrane stabilizer cromoglycate (200 μg/paw, i.pl.) prevented mechanical allodynia (inhibition of 96 ± 21%) and an increase in histamine (44 ± 10% of inhibition) and serotonin (73 ± 5% of inhibition) levels induced by plantar surgery. Finally, local treatment with H(1) (promethazine, 100 μg/paw, i.pl.), 5-HT(3) (ondansetron, 10 μg/paw, i.pl.) or 5-HT(2A) (ketanserin, 5 μg/paw, i.pl.) receptor antagonists partially decreased postoperative nociception in mice, but when co-administered together it completely reversed the mechanical allodynia in operated mice. Thus, mast cell activation mechanisms are interesting targets for the development of novel therapies to treat postoperative pain.