Evaluation of the antiemetic efficacy of maropitant in dogs medicated with morphine and acepromazine

An assessment of the effects of neurokinin1 receptor antagonism against nausea and vomiting: Relative efficacy, sites of action and lessons for future drug development

A broad-spectrum anti-vomiting effect of neurokinin1 receptor antagonists (NK1 RA), shown in pre-clinical animal studies, has been supported by a more limited range of clinical studies in different indications. However, this review suggests that compared with vomiting, the self-reported sensation of nausea is less affected or possibly unaffected (depending on the stimulus) by NK1 receptor antagonism, a common finding for anti-emetics. The stimulus-independent effects of NK1 RAs against vomiting are explicable by actions within the central pattern generator (ventral brainstem) and the nucleus tractus solitarius (NTS; dorsal brainstem), with additional effects on vagal afferent activity for certain stimuli (e.g., highly emetogenic chemotherapy). The central pattern generator and NTS neurones are multifunctional so the notable lack of obvious effects of NK1 RAs on other reflexes mediated by the same neurones suggests that their anti-vomiting action is dependent on the activation state of the pathway leading to vomiting. Nausea requires activation of cerebral pathways by projection of information from the NTS. Although NK1 receptors are present in cerebral nuclei implicated in nausea, and imaging studies show very high receptor occupancy at clinically used doses, the variable or limited ability of NK1 RAs to inhibit nausea emphasizes: (i) our inadequate understanding of the mechanisms of nausea; and (ii) that classification of a drug as an anti-emetic may give a false impression of efficacy against nausea vs. vomiting. We discuss the potential mechanisms for the differential efficacy of NK1 RA and the implications for future development of drugs that can effectively treat nausea, an area of unmet clinical need.

Evaluation of the effectiveness of preoperative administration of maropitant citrate and metoclopramide hydrochloride in preventing postoperative clinical gastroesophageal reflux in dogs

OBJECTIVE

To investigate the prophylactic effectiveness of preoperative administration of maropitant citrate and metoclopramide hydrochloride in preventing postoperative clinical gastroesophageal reflux (GER) in dogs and to identify risk factors for clinical postoperative GER in dogs.

ANIMALS

93 client-owned dogs undergoing surgery at the Washington State University Veterinary Teaching Hospital between March 2016 and February 2017.

PROCEDURES

Dogs were randomly assigned to either the intervention group (preoperatively received maropitant and metoclopramide) or the control group (did not preoperatively receive maropitant and metoclopramide). After surgery, all dogs were recovered and monitored, and occurrences of GER were noted. The prophylactic effectiveness of maropitant and metoclopramide was evaluated, and univariate and multivariate logistic regression analyses were performed to identify variables associated with postoperative clinical GER in dogs.

RESULTS

No meaningful difference in the incidence of clinical GER during the postoperative period was detected between the control and intervention groups. Results indicated that variables associated with significantly increased odds of postoperative clinical GER included the male sex (OR, 9.2; 95% confidence interval [CI], 1.26 to 195.0), an overweight BCS (OR, 12.3; 95% CI, 2.1 to 135.1), gastrointestinal surgery (OR, 30.5; 95% CI, 3.0 to 786.9), and requirement for a dexmedetomidine constant rate infusion after surgery (OR, 9.6; 95% CI, 1.3 to 212.5).

CONCLUSIONS AND CLINICAL RELEVANCE

Findings indicated that incidence of clinical GER during the postoperative period was not lower for dogs that received preoperative prophylactic administration of metoclopramide and maropitant, compared with incidence dogs that did not receive the prophylactic treatment. Further research is required into alternative measures to prevent postoperative clinical GER in dogs.

Assessment of Dog Owner Concern Regarding Peri-operative Nausea and Vomiting and Willingness to Pay for Anti-emetic Treatment

Objective: The objective of this study was to assess dog owners' concern regarding peri-operative nausea and vomiting, and their willingness to pay for treatment.

Design: Descriptive survey.

Sample: A survey was administered to 104 dog owning clients with non-emergent surgical (52) or non-surgical (52) appointments at a University teaching hospital.

Procedure: Descriptive statistics were calculated. A Mann-Whitney U test was used to detect differences between clients expecting their pet to undergo elective general anesthesia and those that did not. A Spearman's Rank Co-efficient was used to correlate predictive data.

Results: Ninety-seven (93%) dog owners had at least some worry regarding their dog experiencing nausea associated with opioid analgesics and anesthesia, with 39/104 (37.5%) moderately to very worried. Forty-one owners (39%) would definitely and 59/104 (56.7%) would likely choose treatment to decrease or prevent signs of nausea. Ninety-four owners (90.4%) had at least some worry regarding vomiting, and 48/104 (46%) indicated they were moderately to very worried. Fifty-three owners (51.4%) would definitely and 49/103 (47.6%) would likely choose treatment to prevent vomiting. The median and mean amount owners were willing to pay was 50 and 76.47 USD, respectively. Ninety-five (91.3%) were likely or very likely to opt for treatment if required to arrive 1 h earlier for their appointment. There was no correlation between age, income, or owner's PONV experience with likelihood of choosing treatment but there was a significant positive correlation with the owner's level of education.

Conclusion: Canine owners are concerned with their pets experiencing nausea and vomiting in relation to opioid analgesics and anesthesia and are willing to pay and stay the required time for effective treatment.

Endogenous Opiates and Behavior: 2016

This paper is the thirty-ninth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2016 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.

Effect of metoclopramide on nausea and emesis in dogs premedicated with morphine and dexmedetomidine

OBJECTIVE

To evaluate whether subcutaneous (SC) metoclopramide (0.2 mg kg^-1) administered 30 minutes prior to (T30) or simultaneously with (T0) intramuscular (IM) morphine (0.2 mg kg^-1) and dexmedetomidine (0.003 mg kg^-1) reduces the incidence of nausea and emesis in healthy dogs.

STUDY DESIGN

Prospective, randomized and blinded study.

ANIMALS

A total of 45 dogs scheduled for elective procedures.

METHODS

Dogs were assigned randomly to three groups to be administered SC metoclopramide (0.2 mg kg^-1) 30 minutes before (group M30) or simultaneously (group M0) to IM morphine (0.2 mg kg^-1) and dexmedetomidine (0.003 mg kg^-1). Dogs in the control group (group C) were administered SC saline at T30 and T0. Dogs were observed for 30 minutes after premedication to evaluate signs of nausea (continuous lip-licking and sialorrhoea) and emesis. Signs of pain or discomfort caused by SC injections were also recorded.

RESULTS

There were no statistical differences amongst groups for age, body weight and sex. More dogs developed continuous lip-licking in group C (12/15, 80.0%) compared to dogs in group M30 (1/15, 6.7%) and dogs in group M0 (5/15, 33.3%; p = 0.0001 and p = 0.01, respectively). More dogs developed sialorrhoea in group M0 (8/15, 53.3%) and in group C (10/15, 66.7%) compared to dogs in group M30 (2/15, 13.3%; p = 0.03 and p = 0.004, respectively). More dogs vomited in group M0 (4/15, 26.7%) and in group C (9/15, 60.0%) compared to dogs in group M30 (0/15, 0.0%; p = 0.05 and p = 0.0003, respectively). None of the dogs demonstrated signs of pain or discomfort during SC metoclopramide injection.

CONCLUSIONS AND CLINICAL RELEVANCE

Subcutaneous metoclopramide at 0.2 mg kg^-1 may reduce IM morphine and dexmedetomidine-induced nausea and emesis if administered 30 minutes in advance. It is effective in reducing lip-licking even when administered concurrently with IM morphine-dexmedetomidine.

Spotlight on the perioperative use of maropitant citrate

Neurokinin-1 (NK-1) receptors are present in both the central nervous system and peripheral tissues. Substance P (SP) is the major ligand and is involved in multiple processes including pain transmission, vasodilation, modulation of the inflammatory response, as well as the sensory neuronal transmission involved in stress, anxiety, and emesis. The involvement of NK-1 and SP in the vomiting reflex has led to the development of NK-1 antagonists to prevent and treat vomiting in human and veterinary medicine. Maropitant is a potent, selective neurokinin (NK-1) receptor antagonist that blocks the pharmacologic action of SP in the central nervous system. Maropitant is available in both an injectable and tablet formulation and approved for use in dogs and cats for the treatment and prevention of vomiting from a variety of clinical causes and motion sickness. When administered prior to anesthetic premedication, maropitant prevents or significantly decreases the incidence of opioid-induced vomiting and signs of nausea in dogs and cats. Maropitant has also been shown to improve postoperative return to feeding and food intake in dogs. The minimum alveolar concentration of sevoflurage is decreased in both dogs and cats by maropitant, indicating a potential role as an adjunct analgesic, especially for visceral pain. This article will review the background information and literature, including clinical recommendations with respect to the perioperative use of maropitant in canine and feline veterinary patients.

Maropitant administered orally 2-2.5 h prior to morphine and dexmedetomidine reduces the incidence of emesis in cats

Objectives The main goal of this study was to test the antiemetic effects of maropitant administered orally 2-2.5 h prior to morphine and dexmedetomidine in cats. Methods Eighty-three healthy female cats were randomized to receive maropitant (8 mg orally; n = 39) or no treatment (control; n = 44), 2-2.5 h prior to morphine 0.1 mg/kg and dexmedetomidine 20 µg/kg intramuscularly. The incidence of sialorrhea, lip licking, retching and vomiting were recorded after morphine/dexmedetomidine injection. Results There were no differences between groups in terms of age or weight. The treated group received a mean ± SD dose of maropitant of 2.9 ± 0.6 mg/kg. The incidence of sialorrhea and lip licking was no different between groups. The incidence of retching (control 36% vs maropitant 13%; P = 0.012) and emesis (control 32% vs maropitant 13%; P = 0.03) was significantly reduced in cats treated with maropitant. Conclusions and relevance Maropitant 8 mg (total dose) administered orally 2-2.5 h prior to morphine and dexmedetomidine significantly reduced, but did not eliminate, the incidences of retching and vomiting. Maropitant did not decrease the occurrence of sialorrhea and lip licking, signs that may be indicative of nausea. Maropitant might be useful for morning administration to prevent emesis in outpatient cats requiring sedation or anesthesia; however, dose regimens or interval of administration might require improvement.