Abstract • 153

During post-transplant period, 5 mg/kg/d (for five days) then 3 mg/kg/d of cyclosporin A (CsA) are administered intravenously and the risk of CsA accumulation is higher because of possible incomplete correction of anemia. So, during the intravenous (IV)-oral (PO) transition period, CsA blood concentrations may be above the therapeutic range because of CsA release from peripheral tissues. We examined 20 children who received bone marrow transplantation (BMT) in our hospital between March 98 and December 98 and for whom bayesian adaptive control of CsA dosage regimens was performed to maintain CsA concentrations in the therapeutic range. We compared CsA dosage regimens during IV-PO transition with CsA dosage regimens administered at equilibration of blood concentrations and clinical status. CsA dosage regimen during IV-PO transition were 4.2 ± 1.3 mg/kg/d in patients treated with Neoral® (n=11) and 3.8 ± 2.0 mg/kg/d in patients treated with Sandimmun® (n=9), while later regimens were respectively 5.7 ± 2.5 mg/kg/d and 6.1 mg/kg/d. Thus, 65% of patients required a once-daily CsAregimen during IV-PO transition whereas it is usually prescribed twice-a-day. IV dosing regimens were not different in the two groups and IV-PO transition doses were not correlated to IV doses neither IV treatment duration. This study shows that the use of standard oral cyclosporin regimens (12 mg/kg/d) after IV treatment could lead to toxic blood concentrations in pediatric BMT, in contrary of solid organ transplants. So bayesian forecasting of PO doses after IV period can be particularly useful. In addition, Neoral® can be given at the same regimen than Sandimmun®. This study confirms the actual tendency to reduce CsA doses, especially in haematological malignancies.