Therapeutic drug monitoring of cyclosporine

Cyclosporine Monitoring

Cyclosporine is an important immunosuppressive agent in organ and bone marrow transplantation. The pharmacokinetics of cyclosporine are quite complex and are complicated by the availability of two assay systems that yield differing results. This article summarizes the views from two major solid organ transplant centers and one bone marrow transplant center on important cyclosporine monitoring questions. A general consensus exists in the four areas discussed that: (1) cyclosporine concentrations must be monitored due in part to the extreme variability in kinetics, (2) either blood or plasma can be used in monitoring programs, (3) the radioimmunoassay or high pressure liquid chromatography can be used in routine monitoring, and (4) the interpretation of cyclosporine concentrations must be performed in relation to patient variables that affect drug response and toxicity.

Cyclosporin A improves brain tissue oxygen consumption and learning/memory performance after lateral fluid percussion injury in rats

Traumatic brain injury (TBI) triggers a complex pathophysiological cascade, leading to cell death. A major factor in the pathogenesis of TBI is neuronal overloading with calcium, causing the opening of mitochondrial permeability transition pores (MPTP), which consequently inhibit normal mitochondrial function. The immunosuppressant Cyclosporin A (CsA) has been shown to block MPTPs, and to be neuroprotective in ischemia and TBI. However, the translation of these effects on mitochondrial function, into behavioral endpoints has not been investigated thoroughly. Therefore, we tested the effect of a low, clinically evaluated, CsA dose of 0.125 mg/kg (infused for 3 h) and a higher "known" neuroprotective dose of 18.75 mg/kg on brain tissue O(2) consumption, and on motor and cognitive performance following lateral fluid percussion injury (FPI) in rats. CsA at both concentrations abolished the 25% decrease in O(2) consumption (VO(2)), seen in saline-treated animals at 5 h post-FPI. Furthermore, the lower dose of CsA also ameliorated acute motor deficits (days 1-5 post-FPI) and learning and memory impairments in a Morris water maze test on days 11-15 post-FPI. Although, the higher dose of CsA improved cognitive performance, it worsened acute motor functional recovery. These results suggest, that the CsA-induced preservation of mitochondrial function, as assessed by tissue O(2) consumption, directly translated into improvements in motor and cognitive behavior.

Controlled release of cyclosporine from VP-HEMA copolymer systems of adjustable resorption monitorized by MEKC

Soluble, uncrosslinked and high molecular weight copolymers of vinylpyrrolidone, VP, with 2-hydroxyethyl methacrylate, HEMA, prepared by free radical copolymerization, are proposed as supports for the modulated release of drugs, taking cyclosporine as a model system. The copolymerization parameters described as reactivity ratios, rVP = 0.08 and rHEMA = 7.97, indicate that the copolymer systems prepared at high conversion have two main components with a microstructural arrangement which depends on the average composition, i.e., an initial HEMA-rich copolymer and a final PVP homopolymer or VP-rich copolymer. This microstructural distribution controls the resorption rate of the polymeric support and therefore the release process of cyclosporine which is demonstrated experimentally by the application of a modern technique known as micellar electrokinetic capillary chromatography (MEKC).

Fluoxetine and cyclosporine in organ transplantation. Failure to detect significant drug interactions or adverse clinical events in depressed organ recipients

Depression and anxiety disorders are common clinical problems in organ transplant recipients, but there is a paucity of clinical data to inform the selection of psychopharmacologic treatment. The authors retrospectively compared 13 depressed organ transplant recipients treated with fluoxetine with 13 nondepressed matched control recipients and 11 transplant recipients treated with tricyclic antidepressants (nortriptyline or desipramine). Blood level:dose ratios and dose-response relationships for cyclosporine were virtually identical in all three groups before and during treatment. No increase in adverse clinical events was detected in either active treatment group compared with the control subjects. Fluoxetine appeared to be well tolerated by this population of transplant patients, and the authors failed to detect significant alterations in cyclosporine levels or graft function.

A simple improved method for the measurement of cyclosporin by liquid-liquid extraction of whole blood and isocratic HPLC

The current HPLC methods of cyclosporin measurement have been reviewed and all aspects assessed. A simple isocratic C-18 reverse phase HPLC method with improved efficiency is described for the routine measurement of cyclosporin in whole blood. An alkaline ether extraction is followed by an acid wash, solvent evaporation and two hexane washes of the reconstituted extract. The turn-round time for a single sample is 1 h. Daily batches of up to 40 patient samples can be easily measured with this method. The results are compared with those from the Sandoz radioimmunoassay (RIA) method.

Saturable binding of cyclosporin A to erythrocytes: estimation of binding parameters in renal transplant patients and implications for bioavailability assessment

Cyclosporin (CyA) exhibits saturable binding to erythrocytes. A one-site binding model was fitted to data from renal transplant patients receiving CyA therapy. The average maximum binding capacity is 2560 micrograms CyA/liter of packed erythrocytes; the unbound CyA concentration associated with 50% saturation of the binding site is 67 micrograms/liter. Analysis indicates that whole-blood CyA measurement to monitor drug therapy should be viewed cautiously, particularly when the hematocrit varies considerably. The error in estimating absolute bioavailability at steady state from whole-blood measurements, resulting as a consequence of the saturable binding, has been explored. Although extrapolation to the therapeutic situation, which involves transient drug administration, is difficult, errors of up to 25% are anticipated. When an accurate estimate of bioavailability is required, analysis based on plasma data is proposed. For bioequivalence testing, both blood and plasma CyA data are equally acceptable.

Cyclosporine monitoring

Cyclosporine is an important immunosuppressive agent in organ and bone marrow transplantation. The pharmacokinetics of cyclosporine are quite complex and are complicated by the availability of two assay systems that yield differing results. This article summarizes the views from two major solid organ transplant centers and one bone marrow transplant center on important cyclosporine monitoring questions. A general consensus exists in the four areas discussed that: cyclosporine concentrations must be monitored due in part to the extreme variability in kinetics, either blood or plasma can be used in monitoring programs, the radioimmunoassay or high pressure liquid chromatography can be used in routine monitoring, and the interpretation of cyclosporine concentrations must be performed in relation to patient variables that affect drug response and toxicity.

Current status of renal transplantation--1986

During the course of 3 decades, and particularly during the past 5 years, clinical renal transplantation has improved to become a safe mode of therapy for end-stage renal disease. Currently, more than 95% 1-year survival can be expected, both in patients who receive allografts from living-related donors and in those who receive cadaver kidneys. One-year living-related donor graft survival is 98%, and 1-year cadaver graft survival is 87%. Cyclosporine has been an important adjunctive immunosuppressive agent not only because of improved results but also because it has shortened hospitalization time.

Cyclosporine blood concentrations determined by specific versus nonspecific assay methods

Cyclosporine blood concentrations were simultaneously determined by radioimmunoassay (RIA) and high-performance liquid chromatography (HPLC) at multiple points in time in two patients receiving cyclosporine for immunosuppression following liver transplantation. Radioimmunoassay levels always exceed those determined by HPLC; however, the divergence between the two methods increased as serum bilirubin concentration increased, with HPLC:RIA ratios generally less than 0.3 when serum bilirubin concentrations exceeded 10.0 mg/dL. These preliminary results suggest that retention of immunoactive cyclosporine metabolites due to imparied liver function may account for RIA-determined cyclosporine concentrations that greatly exceed those measured by HPLC.

Cyclosporine: a review of drug monitoring problems and presentation of a simple, accurate liquid chromatographic procedure that solves these problems

Many studies involving large numbers of patients prove the efficacy of cyclosporine to accomplish immunosuppression following hetertopic organ transplant. In long-term follow-up, cyclosporine produces a higher level of nephropathy than does conventional immunosuppression consisting of azathioprine and prednisone. The degree of nephropathy appears to be related to blood concentration and the effect can be minimized by maintaining therapeutic trough blood concentrations. Other significant side effects (central nervous system toxicity and hirsutism) can also be minimized by low blood concentrations. Development of lymphoma secondary to Epstein-Barr virus exposure is unrelated to blood concentration. Two methods are available for therapeutic drug monitoring: radioimmunoassay (RIA) and high pressure liquid chromatography (HPLC). RIA on plasma is a standard, rapid means of obtaining a result, but that result is inaccurate due to metabolite cross-reactivity. The concentration of cyclosporine in plasma is widely variable and unrepresentative of the whole blood concentration. Plasma concentration is dependent upon the temperature of plasma separation. Whole blood analysis avoids this problem. HPLC procedures allow for whole blood analysis but are tedious and time-consuming. We present here a simple, accurate HPLC procedure that is reproducible (CV = 4.9%), sensitive (to 50 ng/mL), and fast (preparation time - 5.7 minutes, chromatography time - 20 minutes). This procedure correlates (r = 0.98) with a reference HPLC procedure and has been used in our clinical laboratory for analysis of more than 4000 specimens without apparent problem. No interferences have been identified.