We do not have the funding or resources to complete the study at this time

To compare ondansetron, metoclopramide, diphenhydramine, and placebo in order to determine which anti-emetic is most efficacious as a "rescue therapy" for pediatric patients ages 3-18 who have post-operative vomiting after a standardized prophylactic regimen of ondansetron and dexamethasone. We hypothesize that anti-emetics with a different mechanism of action than the prophylactic regimen will be the most effective "rescue therapy" in children having surgery in an ambulatory surgery center.

1. Problem: Despite commonly-used anti-emetics for prophylaxis, some children still go on to develop post-operative vomiting (POV).

   Goal: To determine which anti-emetic--ondansetron, metoclopramide, diphenhydramine, or placebo--is most efficacious for pediatric patients in this situation.

2. Hypothesis: Anti-emetic medications that have a different mechanism of action than the prophylactic regimen will be the most efficacious "rescue therapy."

3. Hypothesis: Metoclopramide at the dose of 0.5 mg/kg (max dose 20 mg) will be more effective than ondansetron, diphenhydramine, or placebo as "rescue therapy."

Inclusion Criteria:

1. Pediatric patients 3-17 years old
2. Patients scheduled for tonsillectomy and/or adenoidectomy (with and without myringotomy) , or dental restoration,
3. Patients receiving a general anesthetic (inhaled agent without nitrous oxide) with POV prophylaxis with two agents (ondansetron and dexamethasone)
4. Post operative vomiting in PACU or second stage recovery requiring antiemetic rescue.

Exclusion Criteria:

1. Vomiting in the past 24 hours or antiemetics in previous 24 hours
2. Allergy or sensitivity to ondansetron, dexamethasone, metoclopramide, or diphenhydramine
3. Patients with diabetes
4. Patients with seizures
5. Patients receiving a benzodiazepine premedication