This research trial will measure how useful Aprepitant is in preventing nausea and vomiting in children having surgery to correct scoliosis (curvature of the spine).

Detailed Description: This prospective, randomized, controlled trial will test whether adding Aprepitant to standard multimodal therapy regimen can further reduce the incidence and severity of post-operative nausea and vomiting (PONV) in children undergoing posterior spinal instrumentation and fusion. The primary outcome of the study will be anti-nausea rescue medication administration post-surgery, with secondary outcomes being the first instance of post-surgery anti-nausea rescue medication administration, emesis, headache, flatus, bowel movement, and sensation of itch; incidence of treatment-emergent adverse events; and worst nausea and pain scores post-surgery .

Inclusion Criteria:

• Posterior Spinal Instrumentation and Fusion (PSIF) for idiopathic scoliosis
• The fusion must include at least 6 vertebral levels.
• Children greater than or equal to 8 years old, and less than 19 years old on the day of surgery
• Weight > 40kg - for ease of pharmacy preparation (PONV dose 1mg per kg to max 40mg)

Exclusion Criteria:

• Patient/ Parent refusal
• Hypersensitivity to Aprepitant or any ingredient in the formulation or oral solution. (previous allergy or adverse reaction to Aprepitant)
• Developmental delay as reported by parents
• Pregnant - Pregnancy test done as standard of care pre-operative
• Severe systemic disease ASA classification III or greater
• Concurrent use of any medication with severe interaction with Aprepitant as outlined in product monograph.
• Neuromuscular or congenital scoliosis
• Inability to take PO medications

Treatment arm of participants will be masked until data collection is complete.