The use of ondansetron for the treatment of nausea in dogs with vestibular syndrome.

Background: Vestibular syndrome is often accompanied by nausea. Drugs currently approved for its treatment have been developed to stop vomiting but not nausea. The efficacy of 5-HT ₃ receptor antagonists to reduce nausea has been described for chemotherapy, but not for nausea secondary to vestibular disorders.
Methods: Sixteen dogs with vestibular syndrome-associated nausea were included in the open-label, multicentre study. The intensity of nausea-like behaviour was analysed before ondansetron administration (0.5 mg/kg i.v.) and 2 h afterwards, using a validated 5-point-scale. The occurrence and frequency of salivation, lip licking, restlessness, vocalisation, lethargy, and vomiting were assessed.
Results: All dogs initially showed signs of nausea, whereas only 31% showed vomitus. The intensity of nausea was significantly reduced in all dogs (p ≤ 0.0001) 2 h after ondansetron administration, including the clinical signs of nausea analysed in 11 dogs (salivation [p = 0.0078], lip licking [p = 0.0078], restlessness [p = 0.0039], and lethargy [p = 0.0078]) except for vocalisation (p > 0.9999).
Conclusions: The results provide preliminary evidence of the potential benefit of ondansetron in the treatment of nausea, which was present in all examined dogs. Vomiting was only observed in 5 dogs indicating that nausea can occur separately and should not be perceived only as a preceding stimulation of the vomiting centre.