Cyclosporine Trough Concentrations Research Articles

Aerosol cyclosporine prevents acute allograft rejection in experimental lung transplantation

Background: The incidence of acute rejection and the morbidity of systemic cyclosporine (INN: ciclosporin) after lung transplantation is significant. Experimental evidence suggests that the allograft locally modulates the immune mechanisms of acute rejection. The purpose of this study was to determine whether aerosolized cyclosporine would prevent acute cellular rejection, achieve effective graft concentrations with low systemic drug delivery, and locally affect production of the inflammatory cytokines involved in acute rejection. Methods: Unilateral orthotopic left lung transplantation was performed in 64 rats (ACI to Lewis), which were divided into eight groups (each group, n = 8): group A, no treatment; groups B to D, aerosol cyclosporine 1 to 3 mg/kg per day, respectively; groups E to H, systemic cyclosporine 2, 5, 10, and 15 mg/kg per day, respectively. After the animals were killed on postoperative day 2, 4, or 6, the transplanted lung, native lung, spleen, and blood were collected. Histologic studies, high-pressure liquid chromatography for trough cyclosporine concentrations, and reverse-transcriptase polymerase chain reaction for cytokine gene expression were performed. Results: Untreated animals showed grade 4 rejection by postoperative day 6. Aerosol cyclosporine prevented acute rejection in a dose-dependent fashion, with group D animals (3 mg/kg per day) showing minimal grade 1 changes. Among animals receiving systemic cyclosporine, only group H (15 mg/kg per day) controlled (grade 1) rejection. However, aerosol cyclosporine, at an 80% lower dose, achieved significantly lower concentrations of cyclosporine in the graft (12,349 vs 28,714 ng/mg, p = 0.002004) and blood (725 vs 3306 ng/ml, p = 0.000378). Group F (systemic 5 mg/kg per day) had higher cyclosporine concentrations in the blood than group D ( p = 0.004572) and similar tissue concentrations ( p = 0.115180), yet had grade 2 rejection. Reverse-transcriptase polymerase chain reaction demonstrated equivalent suppression of inducible nitric oxide synthase but a 20- to 25-fold higher expression of interleukin-6, interleukin-10, and interferon-γ in group D versus group H recipient allografts. Conclusion: Local delivery of cyclosporine by aerosol inhalation dose-dependently prevented acute pulmonary allograft rejection. Effective graft levels and low systemic drug delivery required significantly lower doses than systemic therapy alone. The gene expression of proinflammatory cytokines involved in allograft rejection was suppressed by aerosol cyclosporine therapy. (J Thorac Cardiovasc Surg 1998;115:28-37.)

Cyclosporine monitoring in allogeneic bone marrow transplantation

Objective. To review the benefits and limitations of cyclosporine concentration monitoring to maximize efficacy of graft-versus-host disease prophylaxis and minimize risk of cyclosporine toxicity. Data Sources. A CANCERLIT search of articles published from 1980 to 1995, using the MESH head ings "cyclosporine," and "bone marrow transplant." References listed in the identified publications were reviewed for additional pertinent literature. Study Selection. Human clinical trials and re view articles evaluating cyclosporine pharmacokinet ics and pharmacodynamics in patients status follow ing bone marrow transplantation. Data synthesis. Cyclosporine concentration monitoring has been proposed due to the critical need for drug efficacy, substanial drug-induced toxic ity, and high pharmacokinetic variability. Selection of biological fluid (blood, serum, or plasma) for moni toring as well as the selectivity of the assay employed for cyclosporine versus its metabolites, is a critical factor in evaluating this literature. Both the relation ship between cyclosporine trough concentration and clinical outcome has been evaluated in this patient population. Conclusions. Cyclosporine trough concentra tion monitoring, especially in the blood using an assay specific for the parent compound, has a role in the care of the allogeneic bone marrow transplantation patient. Cyclosporine levels have been correlated with risk for nephrotoxicity and to a lesser extent hepatotoxicity. Low cyclosporine levels are one fac tor contributing to the risk for acute graft-versus-host disease in these patients. Proper evaluation of cyclo sporine levels with due consideration to patient spe cific factors can assist the clinician in maximizing the chances for graft-versus-host disease prevention while reducing the risk of cyclosporine side effects.

Comparison of the dapsone recovery ratio and the erythromycin breath test as in vivo probes of CYP3A activity in patients with rheumatoid arthritis receiving cyclosporine*

Cytochrome P4503A (CYP3A) is primarily responsible for the metabolism of cyclosporine and that of many other drugs. Several substrates of CYP3A have been investigated for use as pharmacologic probes to predict the CYP3A-metabolizing capacity of an individual and, therefore, the disposition of other CYP3A substrate drugs. One such measure of CYP3A activity is the 14C erythromycin breath test, which has been applied to the prediction of cyclosporine disposition. However, the test has practical limitations. Because of this, the 0- to 8-hour urinary dapsone recovery ratio has been studied as an alternative and more practical probe of CYP3A activity. The dapsone recovery ratio and the 14C erythromycin breath test were correlated with cyclosporine concentrations in 16 patients with rheumatoid arthritis to determine the usefulness of the dapsone recovery ratio as an alternative to the 14C erythromycin breath test. The erythromycin breath test showed a fourfold variation between subjects and correlated weakly with trough cyclosporine concentrations (r = -0.50, p < 0.05), whereas the dapsone recovery ratio varied only approximately twofold between subjects and did not correlate with trough cyclosporine concentrations (r = 0.02, p = 0.94). The correlation between the dapsone recovery ratio and the erythromycin breath test (r = 0.22, p = 0.41) was not significant. These data suggest that results obtained with one probe in vivo may not apply to another CYP3A substrate. The poor quantitative relationship between cyclosporine concentrations and the erythromycin breath test limits its usefulness in the prediction of an individual's cyclosporine dose requirement.

Cyclosporin. A review of the pharmacokinetic properties, clinical efficacy and tolerability of a microemulsion-based formulation (Neoral).

The microemulsion-based formulation of cyclosporin (Neoral; referred to as the microemulsion formulation in this review) is a microemulsion preconcentrate which has been developed to overcome problems associated with the poor and unpredictable absorption of the standard oral formulation of this drug. These include marked intra- and interpatient variability in the extent of absorption, a poor correlation between trough blood concentrations of cyclosporin and total systemic exposure, and the need for regular monitoring of blood cyclosporin concentrations. In healthy volunteers and renal or liver transplant recipients, administration of the microemulsion formulation resulted in cyclosporin absorption which was significantly faster, more extensive and more predictable than that seen with the standard oral formulation. Furthermore, measurement of whole-blood trough cyclosporin concentrations provided a better estimate of systemic drug exposure in renal transplant recipients who received the microemulsion formulation than in those who received the standard formulation. Systemic exposure of cyclosporin delivered by the new formulation appears to be relatively unaffected by food intake. Initial data suggest that drug absorption from the microemulsion formulation is enhanced in comparison with that achieved from the standard formulation in liver transplant recipients undergoing biliary diversion or with cholestasis, although absorption from the new formulation does not appear to be completely independent of bile. Preliminary results from other groups that experience cyclosporin malabsorption from the standard formulation (patients with cystic fibrosis or diabetes, and children) are also encouraging. Clinical trials specifically designed to investigate the relative immunosuppressive efficacy of the microemulsion formulation have not been reported; further data are required to fully establish the relationship between the more rapid and extensive absorption of cyclosporin from the microemulsion formulation and the probability of graft rejection or adverse events (including nephrotoxicity and hypertension). However, no statistically significant differences have been noted between the 2 formulations in the incidence of these events in studies to date. The incidence of rejection in new renal or liver transplant recipients treated for a minimum of 3 months was approximately 31 to 50% in those receiving the microemulsion formulation and approximately 24 to 56% in those receiving the standard formulation. Thus, although confirmation of existing efficacy and tolerability data is required, the characteristic pharmacokinetic properties of the microemulsion formulation make it an attractive option for the oral delivery of cyclosporin in transplant recipients, offering more predictable and more extensive drug absorption than the standard formulation. The microemulsion formulation may be of particular benefit in patients who show poor absorption of cyclosporin from the standard oral formulation, such as liver transplant recipients with biliary diversion or cholestasis.

Pharmacokinetics of a New Oral Formulation of Cyclosporine in Liver Transplant Recipients

Trough concentrations of cyclosporine can be highly variable because of its poor bioavailability in current oral formulations, Sandimmune (SIM). Neoral (N-SIM) a new microemulsion of cyclosporine is more readily absorbed than SIM in healthy controls. The present study compared the pharmacokinetic profiles of SIM and N-SIM following orthotopic liver transplantation. In 16 patients with partial biliary diversion, 1 week after transplantation, the bioavailability and peak concentration of a single 300 mg dose of N-SIM were greater than SIM by 724% (p = 0.0019) and 800% (p = 0.0001), respectively. In 39 patients who were on stable doses of cyclosporine 1 month after transplantation, the bioavailability of N-SIM was higher than that of SIM under both fasting (+64%, p = 0.001) and fed (+37%, p = 0.004) conditions. Trough concentrations were similar for the two formulations. However, peak concentrations were higher for N-SIM in both fasting (+119%, p = 0.003) and fed (+53%, p = 0.003) patients. Also, time to peak was shorter for N-SIM in both fasting (-21%, p = 0.027) and fed (-59%, p = 0.0001) patients. The correlation between trough concentrations and bioavailability was greater for N-SIM than for SIM in fasted (r = 0.80, p = 0.0001 versus r = 0.75, p = 0.0001) and fed patients (r = 0.65; p = 0.002 versus r = 0.55; p = 0.012). We conclude that the rate of absorption and the bioavailability of N-SIM is significantly and consistently better than SIM and may, therefore, improve the therapeutic index of cyclosporine after liver transplantation.

Fluconazole therapy in transplant recipients receiving FK506.

Fluconazole therapy in transplant recipients receiving FK506.

Cyclosporine Monitoring Improves Graft-Versus-Host Disease Prophylaxis after Bone Marrow Transplantation

The principal objective of this study was to determine whether a relationship exists between trough cyclosporine concentrations measured by HPLC and the development of acute graft-versus-host disease (GVHD) after allogeneic bone marrow transplantation. A retrospective analysis of 59 consecutive human leukocyte antigen-matched bone marrow transplants. Patients received uniform GVHD prophylaxis with cyclosporine and methotrexate. Whole blood trough cyclosporine concentrations were measured at least twice weekly during hospitalization and weekly after discharge. A dedicated bone marrow transplant unit in an academic center. The means of cyclosporine concentrations were assessed for each patient on a weekly basis during the first 50 days after transplant. These means were compared between patients developing grade 2-4 acute GVHD and patients without significant GVHD. Eighteen patients developed acute GVHD at a median of 25 days after bone marrow transplant (range 10-50). There was no correlation between the development of GVHD and patient age, diagnosis, donor age, donor gender, donor-recipient gender mismatch, and time to neutrophil engraftment (> 1000 x 10(6) cells/L). Although mean weekly cyclosporine concentrations were consistently lower in patients developing acute GVHD, the difference in values compared with those of patients with GVHD was not statistically significant. Mean weekly cyclosporine concentrations at the time of neutrophil engraftment were statistically associated with the development of GVHD. Patients with GVHD had mean +/- SD concentrations of 174 +/- 69 ng/mL, significantly lower than 254 +/- 114 ng/mL in patients without GVHD. Furthermore, the rate of GVHD was 82 percent in patients with mean concentrations < 200 ng/mL at the time of neutrophil engraftment as compared with a rate of 34 percent in patients with concentrations > or = 200 ng/mL (relative risk = 2.4). Also, mean cyclosporine concentrations measured during the week of onset of GVHD were significantly lower compared with mean cyclosporine concentrations of all other patients at risk of GVHD during that week. Cyclosporine concentrations are associated with the development of acute GVHD. Patients with HPLC whole blood concentrations < 200 ng/mL are at significantly higher risk of developing GVHD, particularly if these concentrations are observed during the week of neutrophil engraftment. More effective GVHD prophylaxis could be achieved by careful monitoring of cyclosporine concentrations after transplant.

Trough concentrations of cyclosporine in blood following administration with grapefruit juice.

Components of grapefruit juice have been shown to inhibit CYP3A4 activity, the enzyme involved in cyclosporine metabolism. Eleven medically stable patients (seven males, four females) receiving cyclosporine following kidney transplantation were instructed to take their usual dose of cyclosporine with water for 1 week (Phase 1), with grapefruit juice (8 ounces) for 1 week (Phase 2) and again with water for 1 week (Phase 3). Trough blood samples were obtained at the end of each phase for measurement of cyclosporine concentration using a specific monoclonal whole blood radioimmunoassay. Cyclosporine trough concentrations averaged 116.9 +/- 51.6 ng ml(-1) in the first phase, 145.3 +/- 44.7 ng ml(-1) with grapefruit juice (P < 0.05 compared with the first and third phases) and 111.2 +/- 56.1 ng ml(-1) in the third phase. Cyclosporine concentrations increased in 8 of 11 patients when given with grapefruit juice (mean increase 32%; range -4 to 97%) and declined in 10 of 11 when subjects resumed taking cyclosporine with water (mean decrease 27%). These results suggest that grapefruit juice increases trough concentrations of cyclosporine in blood, possibly by inhibiting pre-hepatic gut wall metabolism, and could be useful in optimizing therapy with this drug.

Influence of cyclosporine pharmacokinetics, trough concentrations, and AUC monitoring on outcome after kidney transplantation

To assess the importance of cyclosporine pharmacokinetics on graft outcome and acute rejection episodes, pretransplant and a total of 1868 posttransplant whole-blood cyclosporine pharmacokinetic profiles were performed in 160 consecutive kidney transplant recipients. The following posttransplant pharmacokinetic risk factors were associated with a poorer graft survival and a higher incidence of acute rejection: F, < 25%; clearance, > 325 ml/min; steady-state cyclosporine concentrations, < 350 ng/ml during intravenous infusion; or average cyclosporine concentrations, < 400 ng/ml during the first oral study. Although the discrimination between rejecting and nonrejecting patients was greatest for cyclosporine concentrations obtained at 24 hours after drug administration, measurements at 6 and 14 hours, as well as average concentrations, were all highly predictive. Because of the strong association between the cyclosporine concentrations and outcome, an equation is described to provide initial oral dose prediction. Furthermore, this association suggests that improved cyclosporine pharmacokinetic monitoring may aid in improving outcome after kidney transplantation.

Is the Monoclonal Fluorescence Polarization Immunoassay for Cyclosporine Specific? Comparison with Specific Radioimmunoassay

Trough concentrations of cyclosporine (CsA) in whole blood were measured by specific monoclonal 3H-radioimmunoassay (S-RIA) and compared with those obtained by monoclonal fluorescence polarization immunoassay (S-FPIA) in 89 transplant recipients. Differences in the S-RIA:S-FPIA relationship between kidney transplant (KT, n = 59) and heart transplant (HT, n = 24) recipients were investigated. Mean concentrations of CsA were significantly higher by S-FPIA than by S-RIA [191 +/- 127 vs. 166 +/- 124 ng/ml (mean +/- SD), p less than 0.001], with a S-FPIA:S-RIA ratio of 1.25 +/- 0.33. Higher ratios were observed either in patients with low CsA concentrations or in those with a high proportion of metabolites. HT recipients had higher S-FPIA:S-RIA ratios than did KT recipients (1.37 vs. 1.22, t = 1.87, p = 0.065). Within-assay coefficients of variation were lower for S-FPIA than for S-RIA (2.4% vs. 12.3%, p less than 0.001). Monoclonal FPIA is a precise and fast method, more suitable than RIA for therapeutic CsA monitoring in clinical practice. However, our results indicate a 25% higher mean CsA concentration by S-FPIA than by S-RIA (37% in HT recipients), which should be borne in mind until therapeutic and toxic ranges are established or a more specific FPIA method is developed.

PHARMACODYNAMIC STUDIES OF CYCLOSPORINE IN MARROW TRANSPLANT RECIPIENTS

We investigated the correlation between trough cyclosporine concentration in plasma measured by polyclonal fluorescence polarization immunoassay (FPIA) and polyclonal radioimmunoassay (RIA) or in whole blood measured by high-performance liquid chromatography (HPLC) and the risk of renal dysfunction or acute graft-versus-host disease in 29 patients undergoing allogeneic bone marrow transplantation for leukemia. The FPIA and RIA values were highly correlated (r = 0.93) and on the average CsA concentrations measured by FPIA were 1.56 times higher than those measured by RIA. Ten patients developed renal dysfunction and 10 developed grades II-IV acute GVHD. Although univariate analysis showed that plasma CsA concentrations measured by either FPIA or RIA were significantly correlated with renal dysfunction, the association was stronger with FPIA. Plasma CsA concentrations measured by FPIA but not RIA remained a significant risk factor for renal dysfunction in a multivariate relative risk model. Amphotericin therapy was significantly associated with renal dysfunction in the univariate analysis but not in the multivariate analysis. No significant associations were found between whole blood CsA or CsA M1 concentration, patients' age, gender, or CsA dose and the risk of renal dysfunction. None of the covariates analyzed significantly correlated with the development of acute GVHD. These data suggest that plasma CsA concentrations measured by nonspecific assays may more accurately correlate with renal dysfunction than whole-blood CsA concentrations measured by HPLC in marrow transplant recipients.

Abbreviated kinetic profiles in area-under-the-curve monitoring of cyclosporine therapy

Abbreviated kinetic profiles can reduce the number of phlebotomies and drug assays, and thereby the cost of area-under-the-curve (AUC) monitoring. In the present investigation, we used two independent data sets: group 1, 101 AUC profiles from 77 stable renal-transplant patients, which included a 5-h sample in addition to the usual 0-, 2-, 4-, 6-, 10-, 14-, and 24-h samples; and group 2, 100 profiles from 50 stable renal-transplant patients before and after a change in their daily oral dose of cyclosporine. Group I demonstrated a fair correlation between cyclosporine trough concentrations and the AUC calculated from a complete set of seven concentrations (r2 = 0.820 and 0.758 for the 24- and 0-h samples, respectively). Stepwise multiple linear-regression analysis revealed that the abbreviated set of three time points (2, 6, and 14 h) explained 96% of the variance in AUC values calculated from the full set of seven samples; additional time points increased the accuracy only slightly. For group 2, we examined the difference between the observed and the predicted concentrations by linear extrapolation; the error in the observed AUC value, compared with the predicted value calculated from seven time points (-13.2% to -1.2%), was similar to the error from just three time points (-11.5% to 4.5%). Abbreviated AUC profiles involving three time points used with a model equation seem to provide a reliable alternative to full seven-point profiles.

Comparison of Cyclosporine Blood Levels Measured by Radioimmunoassay and TDx Assay Using Monoclonal Antibodies

Whole blood steady-state trough concentrations of cyclosporine were measured by radioimmunoassay (RIA) and TDx assays employing monoclonal antibodies in 82 samples from 39 renal transplant patients. Intra- and interassay coefficients of variation for the new TDx technique averaged 3.2 and 5.4%, respectively. In the concentration range of 40 to 717 ng/ml, there was a linear correlation (r = 0.884, p less than 0.001) between both assays [slope of 0.863; y intercept (RIA values) = 15 ng/ml], indicating that the methods can be used interchangeably. Since the automated TDx assay is faster and causes less waste problems, this reliable technique offers some definite advantages for routine clinical use.

INTERACTION BETWEEN CYCLOSPORINE AND FLUCONAZOLE IN RENAL ALLOGRAFT RECIPIENTS

To determine the effect of fluconazole on cyclosporine concentrations, we used a randomized, double-blind, placebo-controlled study design to evaluate 16 stable renal transplant recipients receiving a constant cyclosporine dose. The two groups of patients were given identical capsules of either placebo or fluconazole 200 mg daily for 14 days. Compliance with the protocol was ensured by watching each patient take all the drug doses. Frequent whole-blood cyclosporine trough concentrations, measured by high-performance liquid chromatography, and two area under the blood concentration time curves were determined before and after 14 days of fluconazole or placebo. The results show that cyclosporine trough concentrations, in patients given fluconazole, increased from a mean +/- SD of 27 +/- 16 to 58 +/- 28 ng/ml (P = 0.001) while patients given placebo did not change--35 +/- 26 vs. 37 +/- 35 ng/ml (P = 0.7). Mean cyclosporine AUC increased in the fluconazole patients from 2167 +/- 1039 to 3989 +/- 1675 ng.hr/ml (P = 0.02) while the placebo patients did not change, 3089 +/- 2439 vs. 2954 +/- 2216 ng.hr/ml (P = 0.9). The pre- and post-treatment cyclosporine AUC difference (day 16 minus day 2) for fluconazole vs. placebo was 1822 +/- 1083 vs. -134 +/- 831 ng.hr/ml (P = 0.001). Mean cyclosporine clearance decreased an average of 55% in the fluconazole patients from 1.2 +/- 0.5 to 0.7 +/- 0.4 ml/hr.kg (P = 0.03); the placebo patients did not change--1.4 +/- 1.1 vs. 1.7 +/- 2.3 ml/hr.kg (P = 0.07). During the study period, serum creatinine concentrations did not increase after fluconazole vs. placebo treatment; they were 1.4 +/- 0.3 vs. 1.3 +/- 0.3 mg% (P = 0.8) initially, and 1.4 +/- 0.2 vs. 1.3 +/- 0.3 mg% (P = 0.5) after 14 days. This study indicates that fluconazole 200 mg daily can slowly increase cyclosporine concentrations over two weeks of therapy, approximately doubling the cyclosporine trough concentrations. The management of this interaction requires prospective planning for adjustments in the cyclosporine dosage, guided by cyclosporine concentrations, while transplant recipients are receiving fluconazole.

Investigation of potential interaction of ciprofloxacin with cyclosporine in bone marrow transplant recipients

The effect of the 4-quinolone antimicrobial agent ciprofloxacin on the concentration in plasma and the pharmacokinetics of the immunosuppressive agent cyclosporine was studied in 10 bone marrow transplant recipients. There were no statistically or clinically significant changes in cyclosporine trough concentrations or areas under the concentration-time curve following oral doses of 500 mg of ciprofloxacin every 12 h for 4 days. The data suggest a lack of relevant pharmacokinetic interaction of ciprofloxacin with cyclosporine. There was no indication of an enhanced nephrotoxicity for this drug combination.

Influence of lovastatin on the pharmacokinetics, toxicity and immunologic response of cyclosporine in the obese zucker rat

The combined use of lovastatin, a hypolipidemic agent effective in the reduction of cholesterol levels, and the lipophilic immunosuppressant, cyclosporine, was studied in the obese rat model. Pharmacokinetics, immunosuppressive activity, lipid levels, and creatinine clearances were compared between groups administered drug-free vehicle, lovastatin or cyclosporine alone, or concomitant cyclosporine and lovastatin. All groups were pre-treated with either oral lovastatin 2.5 mg kg-1 day-1 or propylene glycol vehicle for 1 week. Although no differences in renal function were observed in rat groups administered cyclosporine or lovastatin alone, there was a significant reduction in baseline creatinine clearance following combination therapy compared to placebo controls (70 +/- 18 vs 121 +/- 16 per cent of baseline; p less than 0.05). No differences in trough cyclosporine concentrations were observed between groups. Similarly, mean areas under the whole blood concentration-time profiles were not significantly different with or without concomitant lovastatin (61823 +/- 27295 vs 41470 +/- 10312 ng h ml-1; p = 0.13). No differences in systemic clearance or volume of distribution of parent cyclosporine were observed with combination therapy. Furthermore, lipid levels and T-lymphocyte activity were unchanged with the addition of lovastatin. Per cent increases in creatine kinase were significantly correlated with percentage drop in baseline renal function, suggesting the development of rhabdomyolysis. The present data support the interaction between cyclosporine and lovastatin observed clinically, resulting in acute renal dysfunction. Caution should be exercised in their combined use.

Pharmacokinetics and clinical tolerance of intravenous and oral cyclosporine in the immediate postoperative period.

The clinical tolerance and pharmacokinetics of cyclosporine during a prolonged intermittent intravenous infusion (3.5 mg/kg/day three times) followed by an 8 mg/kg daily oral dose was evaluated in eight renal transplant recipients in the immediate postoperative period. Cyclosporine was analyzed from whole blood samples by HPLC. Despite peak drug concentrations of 1463 +/- 754 ng/ml during the infusion period, no adverse pulmonary effects were noted; renal function, urine output, and mean arterial pressure also appeared to have been unaffected. The mean trough cyclosporine concentration was 141 +/- 50 ng/ml; however, two patients had trough values below sensitivity. Kinetic analysis after the third dose of intravenous cyclosporine revealed a mean total body clearance of 0.31 +/- 0.1 L/min and a volume of distribution of 2.88 +/- 1.1 L/kg, whereas the elimination half-life was 12.8 +/- 3.8 hours and the mean residence time was 9.5 +/- 5.1 hours. After conversion to oral therapy the bioavailability ranged from 0.11 to 0.47, with a mean value of 0.27. Subsequently there was an unpredictable pattern of bioavailability within patients, with mean values of 0.27 +/- 0.13 and 0.30 +/- 0.25 during the second and third oral study periods, respectively. These data suggest that despite adjusting the intravenous cyclosporine dosage to account for acute changes in patient body weight, variable kinetics may result in subtherapeutic trough values, even when cyclosporine is administered by prolonged infusion. The clinical implications of fluctuating cyclosporine bioavailability and a potential alternative approach to dosing are discussed.

Serum cyclosporine concentration and risk of acute graft-versus-host disease after allogeneic marrow transplantation.

To determine the relation between the serum cyclosporine concentration and the risk of acute graft-versus-host disease (GVHD), we studied 179 recipients of bone marrow grafts from HLA-identical sibling donors who received prophylaxis with cyclosporine, either by itself or combined with methotrexate. Cyclosporine was given either orally or intravenously at full doses from the day before transplantation until day 50; it was then tapered off and discontinued on day 180. Trough concentrations of serum cyclosporine were measured by radioimmunoassay. The relation between patients' characteristics and the risk of acute GVHD was analyzed with a relative-risk regression model. In 66 patients (37 percent), grades II to IV of acute GVHD developed 7 to 66 days (median, 13) after transplantation. The trough cyclosporine concentration for a given week was significantly associated with the risk that acute GVHD would develop during the following week. The relative risks were 0.7 (i.e., there was a 30 percent reduction in risk) for every increase of 100 ng per milliliter in cyclosporine concentration and 1.0, 0.60, and 0.20 for concentrations of less than 100, 100 to 199, and 200 or more ng per milliliter, respectively (P less than 0.01). A patient's age, prophylaxis regimen, and year of transplantation also influenced the risk of acute GVHD significantly. These data indicate that low cyclosporine concentrations can be a cause of treatment failure and that concentrations should be monitored in recipients of marrow transplants.

Correlation of serum cyclosporine concentration with renal dysfunction in marrow transplant recipients.

We retrospectively analyzed the relationship of serum cyclosporine concentration to renal dysfunction in 63 marrow transplant recipients who received cyclosporine for prophylaxis of acute graft-versus-host disease. Patients were divided into three groups according to their mean trough cyclosporine concentration for the first 28 days of therapy: less than 150, 150-250, and greater than 250 ng/ml. Baseline renal function and exposure to nephrotoxic antibiotics was comparable in the three groups. Renal dysfunction was defined as doubling of baseline serum creatinine. The likelihood of developing renal dysfunction was analyzed with Kaplan-Meier product limit estimates. The log-rank test was used to compare the three groups. Fifty-four (86%) of the patients developed renal dysfunction. The incidence of renal dysfunction was 73%, 95%, and 100%, and it developed at a median of 46, 29, and 20 days in patients with a mean trough concentration of less than 150, 150-250, and greater than 250 ng/ml, respectively (P less than 0.001). Eight of the nine patients who did not develop renal dysfunction had a mean trough concentration of less than 150 ng/ml. These data indicate that the incidence and the rate of development of renal dysfunction are related to serum cyclosporine concentration.