Therapeutic monitoring of cyclosporine in kidney transplantation: the Halifax experience

Single time point measurement by C2 or C3 is highly predictive in cyclosporine area under the curve estimation immediately after lung transplantation

BACKGROUND

The two h post-dose cyclosporine (CsA) concentration has been advocated as the optimal time point measurement for CsA area under the curve (AUC) estimation after solid organ transplantation. The aim of the study was to investigate whether intensified CsA monitoring is necessary, or if a single time point measurement is accurate to estimate the AUC in the very early period following lung transplantation (LuTX).

METHODS

Within the first two wk following transplantation, daily AUCs were calculated by serial CsA measurements at zero, one, two, three, four, and six h (C0-C6) in 12 consecutive lung transplant recipients. Correlation of single CsA measurements and AUC as well as linear regression analysis was performed to evaluate the most predictive single CsA blood level regarding the AUC.

RESULTS

A total of 606 CsA concentration measurements were performed and the 101 corresponding AUCs were calculated for each patient. Mean AUC was 3443 +/- 1451 microg/L. C0: 361 +/- 118 microg/L, C1: 481 +/- 231 microg/L, C2: 682 +/- 314 microg/L, C3: 715 +/- 347 microg/L, C4: 658 +/- 271 microg/L, C6: 571 +/- 260 microg/L. The correlation of CsA serum levels with AUC was the lowest at trough levels (C0) with a correlation coefficient (r = 0.31) and highest at three h (C3: r = 0.89) and two h (C2: r = 0.88).

CONCLUSIONS

Similar to a stable post-transplant period, CsA trough levels turned out to have poor correlation with the corresponding AUC early after LuTX. The highest correlation of C3 with the AUC may be explained by delayed intestinal resorption immediately post-operative, however C2 is a peer parameter. Optimum AUCs and corresponding C2 or C3 levels in the immediate post-operative phase however remain to be determined.

Cyclosporine monitoring in renal transplant recipients with induction therapy: C2 levels in patients monitored on C0

The aim of this retrospective study was to compare the cyclosporine C(2) blood levels in renal transplant recipients with induction therapy, monitored on C(0) levels during the early and long-term post-transplantation periods in different French transplantation centres, to the target values recommended by the International Consensus on Neoral and used in the Mo2art study. A retrospective study was conducted by the therapeutic drug monitoring (TDM) committee of the French Pharmacological Society. Cyclosporine C(0) and C(2) concentrations from 168 renal transplant recipients were collected at different post-transplantation periods by six TDM laboratories of transplantation centres from April 2001 to April 2002. Cyclosporine blood levels were determined by fluorescence polarization immunoassay (mFPIA, AxSYM, Abbott) or enzyme immunoassay (EMIT, Dade Behring). Most patients had C(0) values in the recommended target ranges, with C(2) levels below the targets used in the Mo2art study or proposed by the International Consensus Conference, both during the early and long-term post-transplantation periods. Sixty-eight per cent of patients had C(2) below 1,500 microg/L +/- 20% in the first 2 months post-transplantation and 55% had C(2) below 800 microg/L +/- 20% in the late post-transplantation period (>1 year). Cyclosporine dose should be increased by 40% on average during the first week post-transplantation period and by 50% during the maintenance period to achieve the C(2) targets. In France, most renal transplant recipients receiving induction agents monitored on C(0) had C(2) levels below the targets recommended by the International Consensus Conference. In clinical practice, the optimal therapeutic windows for CsA monitoring based on C(2) needs to be more precisely defined, both during the early and long-term post-transplantation periods in renal transplant recipients receiving induction agents.

Is Absorption Profile of Cyclosporine Really Important for Effective Immunosuppression?

The clinical significance of cyclosporine (CsA) concentration 2 h postdose (C(2)) monitoring is widely recognized in organ transplantation, because C(2) value is considered to be a predictable surrogate marker of full area under the concentration-time curve (AUC), and/or a peak concentration value exhibits potent inhibition of calcineurin activity. However, the pharmacological advantage of absorption profile (AP) has not been fully elucidated. In a rat skin allotransplantation model, the authors evaluated the efficacy of AP by different dosage regimens (20, 25 or 30 mg/kg/d, once or twice daily) and routes (p.o. or i.v.), and examined whether high C(2) or AUC(0-4) is intrinsically valuable for effective immunosuppression. Graft survival was CsA dose-dependent and correlated with full AUC(0-24), rather than AP. The difference between the once and twice daily administrations did not influence full AUC(0-24) or immunosuppressive effect. Continuous intravenous infusion with flat pharmacokinetics also produced adequate immunosuppression as was observed in enteral administration at the same level of total exposure. The impact of high peak concentration in AP on immunosuppressive effect could not be found. It was suggested that AP would not have intrinsic pharmacodynamic value. However, absorption profiling was considered to be clinically useful in that C(2) value is a good surrogate marker of total exposure (AUC(0-24)).

Immunosuppressant Drug Monitoring: Is the Laboratory Meeting Clinical Expectations?

OBJECTIVE:

To review the literature relating to immunosuppressant drug measurement as performed in therapeutic drug monitoring laboratories associated with transplantation centers and consider whether the assay methods widely used for patient dosage management achieve acceptable quality criteria in the context of other sources of variability with these drugs.

DATA SOURCES:

Articles used were accessed primarily through MEDLINE, as well as references cited in related publications. Searches were restricted to organ transplantation in humans.

STUDY SELECTION AND DATA EXTRACTION:

Emphasis was placed on the literature relating to the quality of immunosuppressant drug assays, their limitations, and evidence of clinical benefit in dosage individualization.

DATA SYNTHESIS:

There is a dilemma evident between the quality of the analytical services offered by some diagnostic immunoassay manufacturers and the ability of a significant number of clinical laboratories globally to select only appropriate assay methods.

CONCLUSIONS:

In many cases, clinical laboratories fail to meet the reasonable clinical expectations required for interpretation of immunosuppressant drug assay results as an adjunct to optimal dosage individualization and patient care.