Useful drugs include Promethazine: For children > 2 years, 0.25 to 1 mg / kg (maximum 25 mg) orally, IM, IV, or rectally every 4 to 6 hours Prochlorperazine: For children > 2 years and weighing 9 to 13 kg, 2.5 mg orally every 12 to 24 hours; for those 13 to 18 kg, 2.5 mg orally every 8 to 12 hours; for those 18 to 39 kg, 2.5 mg orally every 8 hours; for those > 39 kg, 5 to 10 mg orally every 6 to 8 hours Metoclopramide: 0.1 mg / kg orally or IV every 6 hours (maximum 10 mg / dose) Ondansetron: 0.15 mg / kg (maximum 8 mg) IV every 8 hours or, if the oral form is used, for children 2 to 4 years, 2 mg every 8 hours; for those 4 to 11 years, 4 mg every 8 hours; for those ≥ 12 years, 8 mg every 8 hours Promethazine is an H1 receptor blocker (antihistamine) that inhibits the emetic center response to peripheral stimulants.