Calcineurin antagonists: cyclosporine

The evolution of therapeutic drug monitoring of cyclosporine¹

Whole blood levels 2 hours after Neoral (C₂) administration were observed to correlate better with area under the curve (AUC_0–4) than trough levels (C₀), suggesting that C₂ may be the best single time point predictor of Neoral absorption. Owing to concerns about drug toxicity due to excessive immunosuppression, C₂ adjustments to target blood levels may represent an advance. The present study measured C₂ and levels to determine which correlated more closely with AUC_0–4.

Between August 2003 and July 2004, 40 adult liver transplantations were performed in our center. All patients received Neoral twice daily. They were maintained at a C₀ level of about 200 ng/mL. C₀ levels were measured daily. C₂ levels were estimated on postoperative days 3, 5, 7, 14, and 28. AUC_0–4 performed on postoperative days 3, 7, and 28 was calculated using the trapezoidal rule.

The mean AUC_0–4, C₀, C₁, C₂, C₃, and C₄ were 1100.3 ± 484.8 ng/mL, 197.1 ± 84.7 ng/mL, 240.7 ± 166.2 ng/mL, 307.8 ± 162.6 ng/mL, 302.8 ± 138.9 ng/mL, and 300.3 ± 142.8 ng/mL, respectively. C₂ correlated with AUC_0–4 (R² = 0.868: P < .05) better than C₀ (R² = 0.245: P < .05), C₁ (R² = 0.604: P < .05), or C₄ (R² = 0.583: P < .05).

Neoral dose monitoring according to a mean C₂ range of 307.8 ± 162.6 ng/mL correlated better with AUC_0–4. Further studies are required to determine suitable C₂ levels in liver transplant patients.

The strategies currently used to monitor concentrations of cyclosporine (CsA) in transplanted patients include whole blood trough (C0), total or abbreviated area under the curve (AUC) concentration and population pharmacokinetic approaches. Recently, a single blood concentration measurement at 2 hours (C2) after CsA administration has been shown to be helpful to predict clinical effects during the first weeks after transplantation of liver and kidney grafts. However, this approach has raised multiple questions about pharmacokinetic variability, analytical methods, and organizational requirements. From a pharmacokinetic point of view, the variability of CsA blood concentrations may relate to circadian variations. The present study sought to characterize the circadian variation in C0 and C2 CsA levels among 20 liver transplant recipients during the first 2 weeks posttransplant. All patients received two equal oral doses of CsA microemulsion formulation every 12 hours. Blood samples were collected before and 2 hours after CsA administration in the morning (am) and in the evening (pm). Whole blood concentrations of CsA were assayed using the monoclonal fluorescence polarization immunoassay system. During the first 2 weeks posttransplant, C2 am mean levels were significantly higher than C2 pm levels (542 ± 241 vs 383 ± 182 ng/mL, P = .005), while the C0 am mean level was not statistically different from the C0 pm (285 ± 174 vs 223 ± 124 ng/mL, P = .367). Our results suggest that morning CsA blood samples may afford a better approach to optimize the CsA dosage, especially based on C2 values.