Clinical Trial to Investigate the Efficacy and Safety of Ondansetron (Danset - Adwia) Versus Placebo Plus the Standard of Care in the Treatment of Nausea and Vomiting in Adult Patients With Acute Gastroenteritis

Inclusion Criteria: 1. Male or female patients aged between 18 and 65 years. 2. Patients diagnosed with acute gastroenteritis visiting the emergency room. 3. Patients considered by the attending physician to need an anti-emetic medication. 4. Patients able and willing to provide written informed consent. 5. Patients able and willing to complete the study procedures including compliance with the requirements and restrictions listed in the consent form. Exclusion Criteria: 1. Pregnant or lactating women. 2. Patients who received an anti-emetic medication during the past 24 hours. 3. History of hypersensitivity to any components of ondansetron or metoclopramide injection. 4. History of hypersensitivity to other selective 5HT3 receptor antagonists. 5. Patients with moderate or severe impairment of hepatic function. 6. Patients with moderate or severe renal impairment. 7. Patients with congenital long QT syndrome. 8. Patients who have or may develop prolongation of Qtc, including patients with electrolyte abnormalities, congestive heart failure, bradyarrhythmia, or patients taking other medicinal products that lead to QT prolongation or electrolyte imbalance. 9. Patients with hypokalemia or hypomagnesemia. 10. Patients with signs of subacute intestinal obstruction. 11. Patients currently using apomorphine hydrochloride. 12. Patients currently using levodopa or dopamine agonists. 13. Patients with gastrointestinal hemorrhage, mechanical obstruction, or gastrointestinal perforation. 14. Patients with a known history of neuroleptic- or metoclopramide-induced tardive dyskinesia. 15. Patients with epilepsy. 16. Patients with Parkinson's disease. 17. Patients with confirmed or suspected pheochromocytoma. 18. Patients with a known history of methemoglobinemia with metoclopramide or NADH-cytochrome b5 reductase deficiency. 19. Patients with a history of clinically-significant illness or any other major medical disorder that may interfere with subject treatment, assessment, or compliance with the protocol. 20. Patients with any chronic illness or prior treatment which in the opinion of the investigator should preclude participation in the trial. 21. Receipt of an investigational drug within 6 months prior to screening, or active enrolment in another investigational medication or device trial. 22. Inability to understand and cooperate with the investigators or to give valid consent.