C2 blood concentrations of orally administered cyclosporine in pediatric liver graft recipients with a body weight below 10 kg

Pharmacokinetic studies in adult and pediatric liver transplant recipients have shown that the C 2 monitoring is superior to the traditional determination of CsA trough levels (C 0 ) as an estimate of CsA exposure. However, target reference values for C 2 in very small infants have not been established yet. The objective of our study was to assess the distribution of C 2 levels in the first week following Ltx and to analyze enteral absorption of CsA for this group of patients. We documented CsA C 0 and C 2 levels in 25 infants with a body weight below 10 kg (median 6.8 kg; range 3:0-9:8 kg) in the first 7 days after Ltx. The infants had a median age at transplantation of 7 months (range 0.3-20.0 months). The underlying diagnoses were biliary atresia (n = 17), acute liver failure (n = 4), metabolic disease (n = 4). All children received CsA microemulsion (Neoral, initial 10 mg/kg/day), prednisolone, and two single doses of basiliximab as immunosuppressive drugs. The mean C 0 and C 2 levels were as follows: day 1: C 0 77.0 ± 39.6, C 2 340.5 ± 140.0 ng/mL; day 2: C 0 135.5 ± 53.2, C 2 467.0 ± 168.2 ng/mL; day 3: C 0 146.5 ± 70.8, C 2 519.0 ± 219.1 ng/mL; day 4: C 0 168.5 ± 55.1, C 2 570.0 ± 163.7 ng/mL; day 5: C 0 156.5 ± 38.0, C 2 612.0 ± 132.4 ng/ mL; day 6: C 0 177.0 ± 41.1, C 2 606.0 ± 149.2 ng/mL; day 7: C 0 174.0 ± 27.2, C 2 622.0 ± 98.8 ng/mL (r = 0.82, p < 0.05). This analysis demonstrates that there is a good enteral absorption of CsA in very small children post-Ltx in the early post-operative period. Based on the C 2 levels achieved, we conclude that there is a good correlation between C 0 and C 2 levels even in very small infants.