Modified Pre-operative Oral Doses Acetaminophen Versus Intravenous Acetaminophen

Inclusion Criteria: * Patients ages 3 years to 17 years scheduled for tonsillectomy and adenoidectomy for obstructive sleep apnea with or without additional minor procedures such as sleep endoscopy, unilateral or bilateral myringotomy, insertion of tympanostomy tubes and/or ear exam. ( Minor additional procedures that are frequently combined with tonsillectomy and adenoidectomy but are not commonly considered to have pain that is significantly greater than the tonsillectomy and adenoidectomy). Exclusion Criteria: * Patients who meet University of California Davis Children's Hospital (UCDCH) criteria for Pediatric Intensive Care Unit (PICU) admission: on home oxygen pre-operatively, exhibit airway obstruction when awake (stertor above larynx, stridor at larynx), sleep study with apnea hypoxia index greater than 25 or sleep oxygen saturation nadir \<80%, cardiac disease, difficult intubation. * Patients with a known allergy to acetaminophen * Patients with known hepatic insufficiency or severe hepatic disease * Patients with known Glucose-6-phosphate dehydrogenase (G6PD) deficiency * Patients who are malnourished (ie lower levels of glutathione) * Patients with severe renal impairment as defined by calculated creatinine clearance \<20 ml/min (per modified Schwarz equation) * Patients who are pregnant