1. They are unwilling to use contraception unless tubal ligation, hysterectomy or vasectomy has been performed (in the patient or partner(s)).
2. They are receiving prescriptions for more than 30 oxycodone capsules (or equivalent-see section 6.2) at a time from clinic personnel.
3. Creatinine is >1.7 mg/dL;
4. Transfusions have been received within 2 months of enrollment, or the patient is on a chronic transfusion program; or the patient is likely to begin chronic transfusion therapy in the next two years;
5. Active liver disease is present, as defined by alanine aminotransferase (ALT) or aspartate aminotransferase (AST)>300 units or abnormal and increasing on serial samples;
6. There is a contraindication for potentially immunosuppressive therapy (HIV antibody testing is required for eligibility and a positive test will result in patient ineligibility);
7. Serum B12, ferritin or folate is abnormally low (patients are acceptable after treatment of deficiency states);
8. Hydroxyurea therapy has been or is currently being administered;
9. The patient is pregnant (tested for in all women before randomization) or breast-feeding;
10. S/ß0 thalassemia is known to be present;
11. The patient is receiving theophylline, androgen, estrogen, progestin (except for birth control), calcium channel blockers, danazol, or any other drug suspected to have an anti-sickling effect
12. The patient has a history of cerebrovascular accident (stroke) and has been on a chronic transfusion program
13. The patient has a history of congestive heart failure and has been on a chronic transfusion program
14. There has been failure to obtain informed consent
15. Hemoglobin-A greater than 15%.