Intravenous L-Citrulline for Vaso-occlusive Pain Episode in Sickle Cell Disease

Inclusion Criteria: * Sickle cell disease (all genotypes) * Patients with sickle cell disease ages 4 to 21 years old * Presence of sickle cell vaso-occlusive pain episode requiring hospitalization and parenteral opioid therapy * Able to randomize to study drug/placebo within 12 hours of first dose of parenteral opioid in the Emergency Department Exclusion Criteria: * Current pain lasting \>3 days. * \>9 hospitalizations in the prior year * Presence of any other complication related to sickle cell disease requiring the hospitalization such as splenic sequestration, hepatic sequestration, stroke, transient ischemic attack, etc. * History of opioid use disorder, chronic pain or medical regimen requiring daily opioid use. * Severe anemia (hemoglobin \<6g/dL) * Pregnant (as confirmed by a positive urine pregnancy test) or lactating female. * Alanine/aspartate transferase \>2x upper limit of normal laboratory range for age. * Subject has the following serum creatinine: * Age 4 to 13 years \> 0.9 mg/dL * Age 14 to 17 years 1.0 mg/dL * Age ≥18 years \>1.5mg/dL * Presence of acute chest syndrome, sepsis, bacterial infection, hemodynamic instability * Use of L-glutamine * History of allergic reaction to L-citrulline products