Sickle cell disease is a genetic red blood cell disorder characterized by vaso-occlusion from sickling of red blood cells, that can lead to pain or organ complications such as acute chest syndrome. Sickle cell disease is associated with low amounts of nitric oxide, a compound important for dilating the blood vessel wall. Citrulline is a substance that is known to increase nitric oxide. The goal of this Phase I study are to find the highest safe dose of continuous IV citrulline that can be given to individuals with sickle cell disease experiencing a sickle cell pain crisis or acute chest syndrome without causing severe side effects.

Inclusion Criteria:

1. Sickle cell disease genotypes (HbSS, HbS/β0-thalassemia, HbS/β+-thalassemia, HbSC)
2. Ages 6 to 50 years old
3. Patients with sickle cell disease aged 6 to 50 years old Presence of sickle cell pain crisis defined by the presence of pain requiring hospitalization and parental opioid therapy
4. Presence of acute chest syndrome defined by the presence of a new CXR infiltrate and any one of the following respiratory symptoms of fever, shortness of breath, wheezing, chest pain, cough or new onset hypoxia.

Exclusion Criteria:

1. Presence of any other complication related to sickle cell disease requiring hospitalization such as splenic sequestration, hepatic sequestration, stroke, avascular necrosis of the hip/shoulder, acute priapism, etc.

2. Severe anemia (hemoglobin < 5g/dL)

3. History of red blood cell transfusion within the last 30 days

4. Systemic steroid therapy within the last 48 hours

5. Pregnant (as confirmed by a negative urine pregnancy test) or lactating female

6. Alanine/aspartate transferase >2x upper limit of normal laboratory range for age.

7. Subject has the following serum creatinine:

   • Age 6 to 13 years > 0.9 mg/dL
   • Age 14-17 years 1.0 mg/dL
   • Age 18 years >1.5mg/dL

8. Patients with an inability to give consent will be excluded

Adverse events were collected up to 4 weeks from study drug administration