Immunologic recovery in thalassemic marrow graft recipients following high-dose busulfan and cyclophosphamide

A Clinical Decision Support Tool to Find the Best Initial Intravenous Cyclosporine Regimen in Pediatric Hematopoietic Stem Cell Transplantation

To optimize cyclosporine A (CsA) dosing regimen in pediatric patients undergoing hematopoietic stem cell transplantation (HSCT), we aimed to provide clinicians with a validated decision support tool for determining the most suitable first dose of intravenous CsA. We used a 10-year monocentric data set of pediatric patients undergoing HSCT. Discretization of all variables was performed according to literature or thanks to algorithms using Shannon entropy (from information theory) or equal width intervals. The first 8 years were used to build the Bayesian network model. This model underwent a 10-fold cross-validation, and then a prospective validation with data of the last 2 years. There were 3.3% and 4.1% of missing values in the training and the validation data set, respectively. After prospective validation, the Tree-Augmented Naïve Bayesian network shows interesting prediction performances with an average area under the receiver operating characteristic curve of 0.804, 32.8% of misclassified patients, a true-positive rate of 0.672, and a false-positive rate of 0.285. This validated model allows good predictions to propose an optimized and personalized initial CsA dose for pediatric patients undergoing HSCT. The clinical impact of its use should be further evaluated.

Higher plasma bilirubin predicts veno-occlusive disease in early childhood undergoing hematopoietic stem cell transplantation with cyclosporine

AIM: To analyze the association between plasma bilirubin levels and veno-occlusive disease (VOD) in non-adult patients undergoing hematopoietic stem cell transplantation (HSCT) during cyclosporine therapy.

METHODS: A total of 123 patients taking cyclosporine were evaluated using an electronic medical system at the Seoul National University Children’s Hospital from the years 2004 through 2011. Patients were grouped by age and analyzed for incidence and type of adverse drug reactions (ADRs) including VOD.

RESULTS: The HSCT patients were divided into three age groups: G#1 ≥ 18; 9 ≤ G#2 ≤ 17; and G#3 ≤ 8 years of age). The majority of transplant donor types were cord blood transplantations. Most prevalent ADRs represented acute graft-vs-host disease (aGVHD) and VOD. Although the incidences of aGVHD did not vary among the groups, the higher frequency ratios of VOD in G#3 suggested that an age of 8 or younger is a risk factor for developing VOD in HSCT patients. After cyclosporine therapy, the trough plasma concentrations of cyclosporine were lower in G#3 than in G#1, indicative of its increased clearance. Moreover, in G#3 only, a maximal total bilirubin level (BILmax) of ≥ 1.4 mg/dL correlated with VOD incidence after cyclosporine therapy.

CONCLUSION: HSCT patients 8 years of age or younger are more at risk for developing VOD, diagnosed as hyperbilirubinemia, tender hepatomegaly, and ascites/weight gain after cyclosporine therapy, which may be represented by a criterion of plasma BILmax being ≥ 1.4 mg/dL, suggestive of more sensitive VOD indication in this age group.

Cyclosporine use in hematopoietic stem cell transplantation: pharmacokinetic approach

Cyclosporine is one of the most vital agents in the process of successful allogeneic hematopoietic stem cell transplantation. Despite a long history and worldwide extent of cyclosporine use for prevention of graft versus host disease, currently there are lots of uncertainties about its optimal method of application to reach the best clinical outcome. A major portion of this problem stems from complicated cyclosporine pharmacokinetics. Study of cyclosporine pharmacokinetic behavior can significantly help recognition of its effectiveness and consequently, optimization of dosing, administration, monitoring and management of adverse effects. In this review, highly accredited but sparse scientific data are gathered in order to provide a better insight for preparation of practice guidelines and directing future studies for allogeneic hematopoietic cell recipients.

Bayesian approach for the estimation of cyclosporine area under the curve using limited sampling strategies in pediatric hematopoietic stem cell transplantation

BACKGROUND

The optimal marker for cyclosporine (CsA) monitoring in transplantation patients remains controversial. However, there is a growing interest in the use of the area under the concentration-time curve (AUC), particularly for cyclosporine dose adjustment in pediatric hematopoietic stem cell transplantation. In this paper, we develop Bayesian limited sampling strategies (B-LSS) for cyclosporine AUC estimation using population pharmacokinetic (Pop-PK) models and investigate related issues, with the aim to improve B-LSS prediction performance.

METHODS

Twenty five pediatric hematopoietic stem cell transplantation patients receiving intravenous and oral cyclosporine were investigated. Pop-PK analyses were carried out and the predictive performance of B-LSS was evaluated using the final Pop-PK model and several related ones. The performance of B-LSS when targeting different versions of AUC was also discussed.

RESULTS

A two-compartment structure model with a lag time and a combined additive and proportional error is retained. The final covariate model does not improve the B-LSS prediction performance. The best performing models for intravenous and oral cyclosporine are the structure ones with combined and additive error, respectively. Twelve B-LSS, consisting of 4 or less sampling points obtained within 4 hours post-dose, predict AUC with 95th percentile of the absolute values of relative prediction errors of 20% or less. Moreover, B-LSS perform better for the prediction of the 'underlying' AUC derived from the Pop-PK model estimated concentrations that exclude the residual errors, in comparison to their prediction of the observed AUC directly calculated using measured concentrations.

CONCLUSIONS

B-LSS can adequately estimate cyclosporine AUC. However, B-LSS performance is not perfectly in line with the standard Pop-PK model selection criteria; hence the final model might not be ideal for AUC prediction purpose. Therefore, for B-LSS application, Pop-PK model diagnostic criteria should additionally account for AUC prediction errors.

The safety and efficacy of acute graft-versus-host disease prophylaxis with a higher target blood concentration of cyclosporine around 500 ng/mL

Cyclosporine (CsA) is the most widely used immunosuppressive agent for the prevention of acute graft-versus-host disease (GVHD). In a previous report, the incidence of acute GVHD was decreased by increasing the target blood concentration of CsA during a continuous infusion from 300 to 500 ng/mL without excessive toxicities. To confirm these results, we retrospectively analyzed 69 patients who received a continuous infusion of CsA at a higher target CsA level between 450 and 550 ng/mL (CsA500 group) and compared the clinical outcome with 29 patients who received CsA with a lower target concentration between 250 and 350 ng/mL (CsA300 group). The target concentration was determined based on the status of background diseases. Multivariate analysis revealed that the incidence of grade III-IV acute GVHD was significantly lower in the CsA500 group, although the incidence of grade II-IV acute GVHD was not different. Toxicities were equivalently observed between the two groups. Concomitant administration of voriconazole or itraconazole and higher hematocrit were identified as independent significant factors for higher concentration/dose ratio of CsA. The average dose of CsA to maintain CsA level around 500 ng/mL was higher compared with the previous study (3.4 mg/kg vs. 2.7 mg/kg at three wk), probably due to the difference in measuring method of CsA concentration. We conclude that continuous infusion of CsA with a target level between 450 and 550 ng/mL is a feasible and effective GVHD prophylaxis, but caution should be paid for the difference in measuring method.

Population pharmacokinetics of cyclosporine in transplant recipients

A number of classical pharmacokinetic studies have been conducted in transplant patients. However, they suffer from some limitations, for example, (1) the study design was limited to intense blood sampling in small groups of patients during a certain posttransplant period, (2) patient factors were evaluated one at a time to identify their association with the pharmacokinetic parameters, and (3) mean pharmacokinetic parameters often cannot be precisely estimated due to large intraindividual variability. Population pharmacokinetics provides a potential means of addressing these limitations and is a powerful tool to evaluate the magnitude and consistency of drug exposure. Population pharmacokinetic studies of cyclosporine focused solely on developing limited sampling strategies and Bayesian estimators to estimate drug exposure, have been summarized before, and are, therefore, not a subject of this review. The major focus of this review is to describe factors (demographic factors, hepatic and gastrointestinal functions, drug-drug interactions, genetic polymorphisms of drug metabolizing enzymes and transporters) that have been identified to contribute to the large portion of observed variability in the pharmacokinetics of cyclosporine in transplant patients. This review summarizes and interprets the conclusions as well as the nonlinear mixed-effects modeling methodologies used in such studies. A highly diversified collection of structural models, variability models, and covariate submodels have been evaluated and validated using internal or external validation methods. This review also highlights areas where additional research is warranted to improve the models since a portion of model variability still remains unexplained.

Obesity and psoriasis: inflammatory nature of obesity, relationship between psoriasis and obesity, and therapeutic implications

Obesity, particularly abdominal obesity, is currently considered a chronic low-grade inflammatory condition that plays an active role in the development of the pathophysiologic phenomena responsible for metabolic syndrome and cardiovascular disease through the secretion of proinflammatory adipokines and cytokines. In recent years clear genetic, pathogenic, and epidemiologic links have been established between psoriasis and obesity, with important implications for health. The relationship between the 2 conditions is probably bidirectional, with obesity predisposing to psoriasis and psoriasis favoring obesity. Obesity also has important implications in the treatment of psoriasis, such as a greater risk of adverse effects with conventional systemic drugs and reduced efficacy and/or increased cost with biologic agents, for which dosage should be adjusted to the patient's weight.

An update on the management of severe idiopathic aplastic anaemia in children

The current outlook for a child with severe idiopathic aplastic anaemia (AA) is very much better than in previous decades. In part, this may reflect better differentiation of idiopathic and inherited marrow failure. For children with idiopathic AA and a human leucocyte antigen (HLA)-matched sibling donor (MSD), allogeneic haematopoietic stem-cell transplantation (AHSCT) is the primary therapy of choice, offering long-term disease-free survival of 90%, although graft-versus-host disease remains a cause of long-term morbidity. A greater treatment challenge remains for those children without a MSD. Combination immunosuppressive therapy (IST) is associated with response rates of 70% or more. However, relapse and clonal evolution with transformation to myelodysplasia or acute myeloid leukaemia remain significant problems after IST and long-term event-free survival rates are less impressive. For children who do not have a sustained response to IST, alternate donor AHSCT should be considered. New HLA typing technologies, novel stem cell sources, reduced-intensity conditioning and graft engineering have reduced toxicity and improved the outcome after alternate donor AHSCT. Emerging therapies that capitalise on recent advances in our understanding of the pathophysiology of idiopathic AA and the immunobiology of AHSCT and IST may further improve the long-term outcome of this disease.

Population Pharmacokinetics of Cyclosporine in Chinese Cardiac Transplant Recipients

STUDY OBJECTIVE

To characterize the population pharmacokinetics of cyclosporine in Chinese patients undergoing cardiac transplantation and to identify the demographic and clinical covariates affecting cyclosporine clearance.

DESIGN

Population pharmacokinetic analysis using data from a retrospective chart review.

SETTING

Specialty hospital in Hong Kong for treatment of cardiac and pulmonary diseases.

PATIENTS

Thirty-eight Chinese adult patients (mean age 46 yrs) who had undergone routine cyclosporine therapeutic drug monitoring after cardiac transplantation between January 1, 1991, and December 31, 2003.

MEASUREMENTS AND MAIN RESULTS

Data regarding dosing, demographics, clinical laboratory values, and concurrent drugs were collected retrospectively. Data were included if patients had blood cyclosporine concentrations determined for at least 12 weeks after transplantation; an average of 18 blood samples/patient were collected. Population modeling was performed using a one-compartment linear model with first-order absorption and elimination. Various demographic and clinical covariates were tested for their significant effects on the apparent oral clearance (Cl/F) of cyclosporine. The stability of the final population model was evaluated by using the bootstrap resampling method. Statistically significant associations were observed between Cl/F and each of the following covariates: body weight (BW), use of diltiazem (DIL), and hematocrit value (HCT). The final model was Cl/F=5.00*(1-DIL)+365/HCT+(0.144*BW). The interindividual variabilities of Cl/F and apparent volume of distribution were 14.5% and 40.2%, respectively. The mean parameter estimates obtained from bootstrap analyses were highly consistent with those obtained with the original data set.

CONCLUSION

The estimated Cl/F values of cyclosporine in our Chinese cardiac transplant recipients appeared to be similar to those reported for Caucasian cardiac transplant recipients. Thus, our data provide support that a cyclosporine dosage regimen similar to that in Caucasian patients may be needed in Chinese cardiac transplant recipients. However, further studies are required to determine the optimum cyclosporine dosage regimen in the Chinese population.

Posttransplant day significantly influences pharmacokinetics of cyclosporine after hematopoietic stem cell transplantation

Cyclosporine-based immunosuppression is common after allogeneic hematopoietic stem cell transplantation (HSCT). Elevated cyclosporine concentrations are associated with significant toxicity and often result in the temporary cessation or discontinuation of cyclosporine. Low blood concentrations also result in significant immunologic risks, primarily graft-versus-host disease and loss of stem cell graft. The pharmacokinetics of cyclosporine are highly complex, and maintaining therapeutic and safe cyclosporine concentrations are challenging. Several clinical factors are known to independently influence in vivo cyclosporine pharmacokinetic behavior. However, in the critically ill patient, several of these clinical factors are generally present simultaneously. Unfortunately, there are no studies that have evaluated the combined effects of these clinical factors on cyclosporine disposition in HSCT. The objective of our study is to determine the population pharmacokinetic parameters of intravenous and oral cyclosporine, evaluate the effects of clinical covariates on cyclosporine pharmacokinetics, and develop a model that estimates clearance (Cl) and dose requirements for an individual HSCT patient with these clinical covariates. The authors analyzed 740 cyclosporine steady-state whole blood concentrations in 129 adult patients obtained between day 0 and discharge or 60 days posttransplant, whichever came first. Patients received intravenous cyclosporine at 2.5 mg/kg every 12 hours if body weight was greater than 50 kg, 2.5 mg/kg every 8 hours if less than 50 kg, or 5 to 7.5 mg/kg/d given as a continuous infusion, beginning on day-3. Patients were converted to oral therapy as tolerated. The influence of clinical covariates on the Cl of cyclosporine was tested with a nonlinear mixed effects model (NONMEM). The tested clinical covariates were age, height, body weight on admission, body surface area, sex, type of hematologic malignancy, transplant type, preparative regimen, baseline serum creatinine, T-cell depletion of graft, number of methotrexate doses, day of onset, and maximum grade of acute graft-versus-host disease. The route and frequency of cyclosporine administration, day posttransplant, total bilirubin level, serum creatinine level, actual body weight, presence of concurrent CYP450 enzyme inhibitors and inducers, or nephrotoxins on the day of the cyclosporine blood measurement were also evaluated. Cyclosporine Cl significantly decreased each week posttransplant. The authors found no significant effect of any of the other tested covariates including total bilirubin on Cl. The final regression model for the estimation of Cl is: Cl (L/hr) = ([body weight in kg - 70] * 0.183 + 22.3) * (day posttransplant factor). The corresponding day posttransplant factor estimates are 1.46, 1.32, 1.20, and 1.0 during days 0 to 7, 8 to 14, 15 to 21 and greater than 21 posttransplant, respectively. The interindividual variability in Cl was 27.7%. The dose of intravenous or oral cyclosporine can be calculated using the estimated Cl. Understanding cyclosporine pharmacokinetics and the clinical events that lead to alterations in Cl and exposure is critical in optimizing immunosuppressive therapy. The authors found that cyclosporine Cl significantly decreased posttransplant until day 21. A pharmacokinetics model was developed that incorporates the day posttransplant to predict cyclosporine Cl. Cyclosporine dose requirements in an individual HSCT patient to achieve the desired therapeutic blood target can be estimated using this model.

Effects of iron overload and hepatitis C virus positivity in determining progression of liver fibrosis in thalassemia following bone marrow transplantation

To identify the role of iron overload in the natural history of liver fibrosis, we reviewed serial hepatic biopsy specimens taken annually from patients cured of thalassemia major by bone marrow transplantation. The patients underwent transplantation between 1983 and 1989 and did not receive any chelation or antiviral therapy. Two hundred eleven patients (mean age, 8.7 +/- 4 years) were evaluated for a median follow-up of 64 months (interquartile range, 43-98 months) by a median number of 5 (interquartile range, 3-6) biopsy samples per patient. Hepatic iron concentration was stratified by tertiles (lower, 0.5-5.6 mg/g; medium, 5.7-12.7 mg/g; upper, 12.8-40.6 mg/g dry weight). Forty-six (22%) patients showed signs of liver fibrosis progression; the median time to progression was 51 months (interquartile range, 36-83 months). In a multivariate Cox proportional hazard model, the risk for fibrosis progression correlated to medium hepatic iron content (hazard rate, 1.9; 95% confidence interval [CI], 0.74-5.0), high hepatic iron content (hazard rate, 8.7; 95% CI, 3.6-21.0) and hepatitis C virus (HCV) infection (hazard rate, 3.1; 95% CI, 1.5-6.5). A striking increase in the risk for progression was found in the presence of both risk factors. None of the HCV-negative patients with hepatic iron content lower than 16 mg/g dry weight showed fibrosis progression, whereas all the HCV-positive patients with hepatic iron concentration greater than 22 mg/g dry weight had fibrosis progression in a minimum follow-up of 4 years. Thus, iron overload and HCV infection are independent risk factors for liver fibrosis progression, and their concomitant presence results in a striking increase in risk.

Successful transplant outcome in a morbidly obese patient with acute myeloblastic leukemia

We report a case of matched unrelated bone marrow transplant (BMT) in a morbidly obese patient with acute myeloblastic leukaemia. The challenges presented in the management of this case included the calculation of chemotherapy and radiotherapy doses and the acute presentation of obstructive sleep apnea. Despite these difficulties, an ultimately successful outcome was obtained, indicating that although associated with increased risk of peri-transplant morbidity, obesity need not represent a contraindication to BMT.

Pharmacokinetics of two oral cyclosporin a formulations in clinically stable heart-transplant patients

In order to evaluate the pharmacokinetics of cyclosporine A comparing the traditional (CsA-SCG) with the microemulsion formulation (CsA-ME), 20 clinically stable heart-transplant patients were enrolled in the study. All patients were on a thrice-daily dosage regimen (mean single dose 1.14 +/- 0.4 mgkg(-1)body weight) of CsA-SCG. The steady-state area under the concentration-time curve during a dosage interval was calculated during three sequential periods: (1) the first after the morning oral dose of CsA-SCG; (2) the second (8 days later) after 2 hours intravenous infusion of cyclosporine; (3) the third after the CsA-ME morning oral dose (30 days after the milligram-to-milligram dose conversion). After switching from standard formulation CsA-SCG to CsA-ME, significant changes were observed in C(max)(ss)( 732 +/- 178 vs 935 +/- 250 ng ml(-1), P< 0.001) and t(max)( 2.63 +/- 1.21 vs 1.36 +/- 0.49 h, P< 0.001). The CsA-ME mean bioavailability was higher than CsA-SCG ( 75 +/- 19 vs 66 +/- 16%;P< 0.001). The main CsA pharmacokinetic parameters of both formulations in clinically stable heart-transplant patients presented evident differences from data obtained in other transplant-patient populations.

Parenteral nutrition and cyclosporine: do lipids make a difference? A prospective randomized crossover trial

AIMS

This prospective, controlled, randomized crossover trial was conducted to assess the effects of parenteral nutrition, with or without lipids, in cyclosporine (CyA) pharmacokinetics.

METHODS

10 adult patients were randomized on the day of allogeneic bone marrow transplantation to receive isocaloric and isonitrogenous parenteral nutrition admixtures without (regimen A) or with lipids (regimen B). Admixtures were started on average by day + 7.4; 5 patients received regimen A followed by B, 5 in reverse order. Blood samples were collected at day 4 after transplantation, under oral diet, and 4 days after the initiation of each regimen as the sole nutrition support. At each time point, 8 whole blood samples were analysed for CyA to evaluate: area under the curve (AUC), trough concentration and systemic clearance. Clinical/laboratory events were recorded until 31 months of follow-up.

RESULTS

There was no evidence of a period or treatment-by period interaction, thus results were combined for further analysis. There were no statistically significant differences between regimens in any CyA pharmacokinetic parameters; there were no significant differences from baseline values, except for a higher systemic clearance of CyA with regimen A (0.40+/-0.09 vs 0.29+/-0.06 L/Kg/h, p=0.03).

CONCLUSIONS

The provision of 0.8 g/Kg/d of a 50:50 mixture of medium and long chain triglycerides did not affect CyA parameters, which were closer to baseline. In the short or long term there were no attributable side effects.

Surgical implications of obesity

Obesity is perhaps the most significant public health problem facing the United States today. Obese patients are at increased risk for numerous medical problems, which can adversely affect surgical outcome. However, these risks have not uniformly translated into increased or prohibitive operative morbidity and mortality in this population. With appropriate perioperative precautions and monitoring, the incidence of serious cardiovascular and pulmonary complications can be minimized. Obese patients can be treated as safely and effectively as their normal weight counterparts under most circumstances and should not be denied surgical treatment for any disorder when surgery constitutes the most appropriate therapy. When indicated, surgical treatment should be considered for patients with clinically severe obesity, since currently it appears to offer the best long-term results for weight control and amelioration of comorbidity.

Pharmacokinetics of orally and intravenously administered cyclosporine in pre-kidney transplant patients

The pharmacokinetics of cyclosporine (CSA) and four metabolites were evaluated in eight hemodialysis subjects awaiting renal transplantation to compare metabolic patterns with those observed in post-transplant patients and normal volunteers. Each subject received a single 4-mg/kg intravenous and a single 10-mg/kg oral dose separated by a 1-week washout period. Blood samples were collected before and at .5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 10, 12, 14, and 24 hours after CSA dosing. Cyclosporine blood, plasma, and metabolite (M17, M1, M18, M21) levels were determined by high-pressure liquid chromatography. Mean (+/- standard deviation) CSA blood clearance was .47 +/- .15 L/hour/kg, steady-state volume of distribution (Vss) was 1.9 +/- .5 L/kg, and mean residence time (MRT) was 4.4 +/- 1.8 hours after intravenous dosing. With plasma, mean clearance was .70 +/- .31 L/hour/kg, Vss was 2.4 +/- 1.2 L/kg, and MRT was 3.7 +/- 2.2 hours. Cyclosporine bioavailability (F) averaged 24 +/- 11 and 24 +/- 15%, using blood and plasma, respectively. Values for clearance and Vss were approximately 30 to 100% greater than comparable estimates in healthy volunteers, but F and MRT were not altered to this extent. These changes might be explained on the basis of decreased protein binding in uremic patients. The area under the curve ratio for M17 and M1 to CSA increased an average of 1.7- and 3.9-fold, respectively, after oral dosing compared with intravenous administration, indicating increased conversion during first-pass metabolism.

Pharmacokinetic strategies for cyclosporin therapy in organ transplantation

Marked interindividual variations in cyclosporin (CsA) produce disparate clinical results in organ transplant recipients. In an attempt to eliminate marked deviations of insufficient or excessive CsA concentrations consequent to the administration of uniform drug doses, test dose pharmacokinetics were performed on each potential organ transplant candidate. An intravenous 3 mg/kg test dose delivered over 3 h proved to be readily performed, namely 53% perfect studies, and relatively reliable, namely 73% of observed concentrations within 10% of the predicted values. Furthermore, the use of CsA doses predicted by pretransplant studies reduces the incidence of delayed graft function, early rejection episodes and transplant loss. The oral test dose study predicted a suitable amount of CsA to achieve sufficient gastrointestinal absorption but was less accurate than the iv prediction method: namely, 40% of observed post-transplant concentrations were within 10% of the predicted target value. Furthermore, patients who received oral doses predicted by the test dose strategy showed no improvement in the incidence of acute rejection episodes between 7 and 60 days, and only modestly improved serum creatinine values. The lower accuracy of predictions from oral test dose studies may reflect the impact of non-linear oral (as opposed to iv) drug pharmacokinetics, of variable diet, and/or of altered postoperative gastrointestinal function.

Pharmacokinetics of cyclosporine in bone marrow transplantation: longitudinal characterization of drug in lipoprotein fractions

The pharmacokinetics of cyclosporine (CSA; 2 mg/kg given iv over a period of 2 h every 12 h) in whole blood, plasma, high-density lipoproteins (HDL), and low-density lipoproteins (LDL) were studied after single (n = 10) and multiple (31 days; n = 6) doses in patients receiving allogeneic bone marrow transplants. Whereas HDL-cholesterol levels decreased significantly, LDL-cholesterol levels increased from day 1 to day 31 of CSA dosing. The mean area under the concentration-time curve and half-life values of CSA in whole blood or total plasma did not differ after single or multiple doses. Greater amounts of CSA were contained in the HDL relative to the LDL fraction over the 24-h period after a single dose; the reverse was found after multiple dosing. Cyclosporine was not detectable in the very LDL fractions. The percentage of total plasma CSA contained in each lipoprotein fraction was independent of the concentration of CSA in total plasma or whole blood. The pharmacokinetics of CSA in the various biologic matrices were not associated with measurements of kidney and liver function. Taken together, the variability of CSA pharmacokinetics previously reported in whole blood or total plasma was also found in lipoprotein fractions. The relative changes in CSA content of lipoproteins may offer an explanation for differences in drug effect with multiple dosing.