Study to Compare the Pharmacokinetics of Tacrolimus in Stable Pediatric Allograft Recipients Converted From Prograf® to Advagraf®

Part A: On Day 1 subjects will be converted from their routine Prograf®-based immunosuppressive regimen to a Prograf®-based immunosuppressive regimen supplied by the Sponsor as study medication and continue treatment until Day 7. The daily dose of the study medication must be the same \[1:1 (mg:mg)\] as the Prograf® dose received during the 30-day screening period. On Day 7 the first 24 hour PK profile will be started. Samples will be taken over a 24 hour period and will be completed on Day 8. On Day 8 subjects will be switched to once-daily Advagraf® on a 1:1 (mg:mg) total daily dose basis and continue treatment until Day 14. On Day 14 the second 24-hour PK profile will be started. Samples will be taken over a 24-hour period and will be completed on Day 15. Part B: One year follow-up period to evaluate safety and efficacy of tacrolimus when administered as an Advagraf®-based immunosuppressive regimen. Part C: Continuation of long-term follow-up (from Day 365 onwards). Patients who have completed Part B and to whom continued treatment with Advagraf® is not currently available, will be offered participation in a continuation of long-term follow-up (Part C). Part C will continue until Advagraf® becomes available to these patients or these patients' discontinuation, whichever is the earliest. Part C applies to patients in the following countries: United Kingdom, Czech Republic, Germany, Italy, and Poland only.