Calcineurin activity in children with renal transplants receiving cyclosporine.

BACKGROUND: The major immunosuppressive effect of cyclosporine is through the inhibition of calcineurin, an enzyme important in the activation of T lymphocytes. In children, neither calcineurin activity nor its inhibition by cyclosporine (CsA) has been investigated. METHODS: Calcineurin activity, was measured in stable pediatric renal transplant patients, with healthy children used as controls. Whole blood CsA concentrations were measured by monoclonal radioimmunoassay. Simultaneous calcineurin and CsA levels were measured before and 1, 2, 3.5, 5, and 12 hr after their routine morning CsA dose. RESULTS: Calcineurin activity was approximately 50% inhibited at trough blood concentrations (148 microg/L); moreover, inhibition increased as CsA concentrations rose and declined as concentrations fell. Maximum calcineurin inhibition was about 70% at concentrations of about 431 microg/L. Linear regression analysis revealed a significant correlation between mean CsA blood concentration and the mean degree of inhibition of calcineurin activity (P=0.005, one-tailed). CONCLUSION: We conclude that inhibition of calcineurin activity by CsA in pediatric renal transplant recipients correlates with CsA blood concentrations.

Reduced cyclosporine absorption preceded acute allograft rejection in a child with a liver transplant.

This case report correlates impaired cyclosporine absorption from the traditional oral formulation in a 9-year-old liver transplant recipient with subsequent acute allograft rejection. Although impaired absorption in this patient was documented by cyclosporine pharmacokinetic profiling (steady-state area under the cyclosporine concentration-time curve or AUC), no indication was evident from the pre-dose cyclosporine trough level, which was within the typical target range of blood concentrations. However, when the subject received the microemulsion formulation of cyclosporine the AUC value reflected an adequate absorption pattern. We recommend that if malabsorption is suspected in the de novo pediatric liver transplant patient, then single-sample pre-dose trough cyclosporine levels should not be relied on as an indicator of sufficient immunosuppression and that a limited sampling strategy be used to confirm or rule out impaired absorption.

Absorption characteristics of a microemulsion formulation of cyclosporine in de novo pediatric liver transplant recipients.

In pediatric liver transplant recipients, oral cyclosporine (CsA) therapy may be complicated by impaired or delayed absorption during the initial weeks posttransplant. Neoral (NL) is a microemulsion preconcentrate formulation of CsA expected to increase the rate and extent of absorption of CsA and have less pharmacokinetic variability. The absolute bioavailability (F) of CsA from NL was compared with that of the currently marketed Sandimmune (SM) formulation in a double-blind, crossover study conducted in 9 pediatric liver transplant recipients (age 6 months to 11 years) between 8 and 20 days posttransplant. After determination of CsA pharmacokinetics for a steady-state intravenous dose, patients were randomized to receive a single oral dose of NL or SM in period I and the alternative formulation in period II. Clearance (Clt) and volume of distribution (Vss) values (mean +/- s.d.) calculated from the i.v. dose were similar to that previously reported for pediatric patients (Clt = 12.0 +/- 1.3 ml/min/kg; Vss = 2.2 +/- 0.2 L/kg). Mean F (+/- SD) for NL was significantly higher than SM (NL = 37.6 +/- 14.6%; SM = 24.7 +/- 8.0%; P = 0.05). Although not reaching statistical significance, the observed maximum blood concentration (Cmax) was higher, and the time to Cmax (Tmax) was shorter for NL in 8 or 9 patients. There were no significant correlations between age and any pharmacokinetic parameter for the group as a whole--however, there were statistically significant correlations between age and F for NL (r = 0.87; P = 0.02), and for age and Vss (r = 0.91; P = 0.01) for the 6 patients aged 2 years or less. In this pediatric liver transplant population, Neoral demonstrated improved absorption (% increase in F) compared to Sandimmune. In liver transplant recipients aged 2 years or less, absorption of Neoral may be a function of age and/or bowel length.