Area-under-the-curve monitoring of prednisolone for dose optimization in a stable renal transplant population

Background: Renal transplant recipients were noted to appear cushingoid while on low doses of steroid as part of a triple therapy immunosuppression of cyclosporin A (CsA), prednisolone, and azathioprine. Methods: The study group comprised adult renal transplant recipients with stable graft function who had received their renal allograft a minimum of 1 year previously (43 studies undertaken in 22 men and 20 women) with median daily prednisone dose of 7 mg (range 3-10). The control group was healthy nontransplant subjects [median dose 10 mg (10-30)]. Prednisolone bioavailability was measured using a limited 6-hour area under the curve (AUC), with prednisolone measured using specific HPLC assay. Results: The median prednisolone AUC/mg dose for all transplant recipients was significantly greater than the control group by approximately 50% (316 nmol(.)h/L/mg prednisolone versus 218). AUC was significantly higher in female recipients (median 415 versus 297 for men) and in recipients receiving cyclospotin (348 versus 285). The highest AUC was in women on estrogen supplements who were receiving cyclosporin (median 595). A significantly higher proportion of patients on triple therapy had steroid side effects compared with those on steroid and azathioprine (17/27 versus 4/15), more women than men had side effects (14/16 versus 7/22), and the AUC/mg prednisone was greater in those with side effects than without (median 377 versus 288 nmol-h/L/mg). Discussion: The results are consistent with the hypothesis that CsA increases the bioavailability of prednisolone, most likely through inhibition of beta-glycoprotein. The increased exposure to steroid increased the side-effect profile of steroids in the majority of patients. Because the major contributor to AUC is the maximum postdose concentration, it may be possible to use single-point monitoring (2 hours postdose) for routine clinical studies.

High-Risk Merkel Cell Carcinoma of the Skin Treated With Synchronous Carboplatin/Etoposide and Radiation: A Trans-Tasman Radiation Oncology Group Study-TROG 96:07

Purpose: The effectiveness of synchronous carboplatin, etoposide, and radiation therapy was prospectively assessed in a group of patients with high-risk Merkel cell carcinoma (MCC) of the skin. Patients and Methods: Patients were eligible if they had disease localized to the primary site and nodes, and were required to have at least one of the following high risk features: recurrence after initial therapy, involved nodes, primary tumor size greater than 1 cm, gross residual disease after surgery, or occult primary with nodes. Radiation was delivered to the primary site and nodes to a dose of 50 Gy in 25 fractions over 5 weeks and synchronous carboplatin (area under the curve, 4.5) and intravenous etoposide 80 mg/m(2) days 1 to 3 was given in weeks 1, 4, 7, and 10. The median age of the group was 67 (range, 43-86) years, and there were 39 males and 14 females. Involved nodes (stage II) were present in 33 cases (62%). The sites involved were head and neck (22 patients), occult primary (13 patients), upper limb (eight patients), lower limb (eight patients), and trunk (two patients). Results: Fifty-three patients were entered between 1996 and 2001. The median potential follow-up was 48 months. There were no treatment related deaths. The 3-year overall survival, locoregional control, and distant control were 76%, 75%, and 76%, respectively. Tumor site and the presence of nodes were factors that were predictive for local control and survival. Multivariate analysis indicated that the major factor influencing survival was the presence of nodes; however, this was not a significant factor in locoregional control. Conclusion: High levels of locoregional control and survival have been achieved with the addition of chemotherapy to radiation treatment for high-risk MCC of the skin. The role of chemoradiotherapy for high-risk MCC warrants further investigation. (C) 2003 by American Society of Clinical Oncology.

Blunted prolactin response to D-fenfluramine in post-stroke major depression

Background: This study investigated whether patients suffering from post-stroke depressive disorder had a similar disturbance in central serotonergic function to that described in non-brain injured depressed patients. Methods: Twenty-three depressed patients (nine major, 14 minor) and 38 non-depressed patients were examined 4-8 weeks post-stroke with a structured interview, rating scales and MRI brain scans. Patients were administered 30 mg D-fenfluramine orally and plasma prolactin and D-fenfluramine concentrations were measured for 6 h post-dose. Results: The prolactin response was significantly blunted in major depression compared to minor depression and non-depressed patients as measured by both delta prolactin and area under the prolactin versus time curve. There was no significant relationship between prolactin response and lesion lateralization or any of the measured clinical characteristics. Limitations: The major limitation of the study is the relatively small number in each depressive group. Conclusions: Patients suffering from major depression in the post-stroke period have a blunted prolactin response to D-fenfluramine. This indicates a serotonergic abnormality consistent with that found in major depression where neurological disease is not present. (C) 2003 Elsevier B.V. All rights reserved.

Carboplatin pharmacokinetics following a single-dose infusion in sulphur-crested cockatoos (Cacatua galerita)

Objective To determine the pharmacokinetics of carboplatin in sulphur-crested cockatoos, so that its use in clinical studies in birds can be considered. Design A pharmacokinetic study of carboplatin, following a single intravenous (IV) or intraosseus (10) infusion over 3 min, was performed in six healthy sulphur-crested cockatoos (Cacatua galerita). Procedure Birds were anaesthetised and a jugular vein cannulated for blood collection. Carboplatin (5 mg/kg) was infused over 3 min by the IV route in four birds via the contralateral jugular vein, and by the 10 route in two birds via the ulna. Serial blood samples were collected for 96 h after initiation of the infusion. Tissue samples from 11 organs were obtained at necropsy, 96 h after carboplatin administration. Total Pt and filterable Pt in plasma and tissue Pt concentrations were assayed by inductively coupled plasma-mass spectrometry. A noncompartmental pharmacokinetic analysis was performed on the plasma data. Results The mean +/- SD for the C-max of filterable Pt was 27.3 +/- 4.06 mg/L and in all six birds occurred at the end of the 3 min infusion, thenceforth declining exponentially over the next 6 h to an average concentration of 0.128 +/- 0.065 mg/L. The terminal half-life (T-1/2) was 1.0 +/- 0.17 h, the systemic clearance (CI) was 5.50 +/- 1.06 mL/min/kg and the volume of distribution (Vss) was 0.378 +/- 0.073 L/kg. The extrapolated area under the curve (AUC(0-x)) was 0.903 +/- 0.127 mg/mL.min; the area extrapolated past the last (6 h) data point to infinite time averaged only 1.25% of the total AUC(0-x). The kidneys had the greatest accumulation of Pt (7.04 +/- 3.006 mug/g), followed by the liver (3.08 +/- 1.785 mug/g DM). Conclusions and clinical relevance Carboplatin infusion in sulphur-crested cockatoos produced mild, transient alimentary tract signs and the Pt plasma concentration was similar whether carboplatin was given intravenously or intraosseously. Filterable plasma Pt concentrations for carboplatin persisted longer than for cisplatin, due mostly to the difference in systemic clearance between these drugs in sulphur-crested cockatoos. The distribution of tissue Pt after carboplatin administration was similar to that reported for cisplatin in sulphur-crested cockatoos. Despite anatomical, physiological and biochemical differences among animal species, the pharmacokinetic disposition of filterable Pt in the sulphur-crested cockatoo shares some features with the kinetics reported previously in other animals and human beings.

Sampling times for monitoring tacrolimus in stable adult liver transplant recipients

The aim of this study was to determine the most informative sampling time(s) providing a precise prediction of tacrolimus area under the concentration-time curve (AUC). Fifty-four concentration-time profiles of tacrolimus from 31 adult liver transplant recipients were analyzed. Each profile contained 5 tacrolimus whole-blood concentrations (predose and 1, 2, 4, and 6 or 8 hours postdose), measured using liquid chromatography-tandem mass spectrometry. The concentration at 6 hours was interpolated for each profile, and 54 values of AUC(0-6) were calculated using the trapezoidal rule. The best sampling times were then determined using limited sampling strategies and sensitivity analysis. Linear mixed-effects modeling was performed to estimate regression coefficients of equations incorporating each concentration-time point (C0, C1, C2, C4, interpolated C5, and interpolated C6) as a predictor of AUC(0-6). Predictive performance was evaluated by assessment of the mean error (ME) and root mean square error (RMSE). Limited sampling strategy (LSS) equations with C2, C4, and C5 provided similar results for prediction of AUC(0-6) (R-2 = 0.869, 0.844, and 0.832, respectively). These 3 time points were superior to C0 in the prediction of AUC. The ME was similar for all time points; the RMSE was smallest for C2, C4, and C5. The highest sensitivity index was determined to be 4.9 hours postdose at steady state, suggesting that this time point provides the most information about the AUC(0-12). The results from limited sampling strategies and sensitivity analysis supported the use of a single blood sample at 5 hours postdose as a predictor of both AUC(0-6) and AUC(0-12). A jackknife procedure was used to evaluate the predictive performance of the model, and this demonstrated that collecting a sample at 5 hours after dosing could be considered as the optimal sampling time for predicting AUC(0-6).

Free mycophenolic acid should be monitored in renal transplant recipients with hypoalbuminemia

The current approach for therapeutic drug monitoring in renal transplant recipients receiving mycophenolate mofetil (MMF) is measurement of total mycophenolic acid (MPA) concentration. Because MPA is highly bound, during hypoalbuminemia the total concentration no longer reflects the free (pharmacologically active) concentration. The authors investigated what degree of hypoalbuminemia causes a significant change in protein binding and thus percentage free MPA. Forty-two renal transplant recipients were recruited for the study. Free and total concentrations of MPA (predose, and 1, 3, and 6 hours post-MMF dose samples) and plasma albumin concentrations were determined on day 5 posttransplantation. Six-hour area under the concentration-time curve (AUC(0-6)) values were calculated for free and total MPA, and percentage free MPA was determined for each patient. The authors found a significant relationship between low albumin concentrations and increased percentage free MPA (Spearman correlation = -0.54, P < 0.0001). Receiver operating characteristic (ROC) curve analysis was performed on the albumin versus percentage free MPA data. The cutoff value of albumin determined from the ROC analysis that differentiated normal from elevated percentage free MPA (defined as greater than or equal to3%) in this patient population was 31 g/L. At this cutoff value albumin was found to be a good predictor of altered free MPA percentage, with a sensitivity and specificity of 0.75 and 0.80, respectively, and an area under the ROC curve of 0.79. To rationalize MMF dosing regimens in hypoalbuminemic patients (plasma albumin less than or equal to 31 g/L), clinicians should consider monitoring the free MPA concentration.

Doxorubicin pharmacokinetics following a single-dose infusion to sulphur-crested cockatoos (Cacatua galerita)

Objective To determine the pharmacokinetics of doxorubicin in sulphur-crested cockatoos, so that its use in clinical studies in birds can be considered. Design A pharmacokinetic study of doxorubicin, following a single intravenous (IV) infusion over 20 min, was performed in four healthy sulphur-crested cockatoos (Cacatua galerita). Procedure Birds were anaesthetised and both jugular veins were cannulated, one for doxorubicin infusion and the other for blood collection. Doxorubicin hydrochloride (2 mg/kg) in normal saline was infused IV over 20 min at a constant rate. Serial blood samples were collected for 96 h after initiation of the infusion. Plasma doxorubicin concentrations were assayed using an HPLC method involving ethyl acetate extraction, reverse-phase chromatography and fluorescence detection. The limit of quantification was 20 ng/mL. Established non-parametric methods were used for the analysis of plasma doxorubicin data. Results During the infusion the mean +/- SD for the C-max of doxorubicin was 4037 +/- 2577 ng/mL. Plasma concentrations declined biexponentially immediately after the infusion was ceased. There was considerable intersubject variability in all pharmacokinetic variables. The terminal (beta-phase) half-life was 41.4 +/- 18.5 min, the systemic clearance (Cl) was 45.7 +/- 18.0 mL/min/kg, the mean residence time (MRT) was 4.8 +/- 1.4 min, and the volume of distribution at steady state (V-SS) was 238 131 mL/kg. The extrapolated area under the curve (AUC(0-infinity)) was 950 +/- 677 ng/mL.h. The reduced metabolite, doxorubicinol, was detected in the plasma of all four parrots but could be quantified in only one bird with the profile suggesting formation rate-limited pharmacokinetics of doxorubicinol. Conclusions and clinical relevance Doxorubicin infusion in sulphur-crested cockatoos produced mild, transient inappetence. The volume of distribution per kilogram and terminal half-life were considerably smaller, but the clearance per kilogram was similar to or larger than reported in the dog, rat and humans. Traces of doxorubicinol, a metabolite of doxorubicin, were detected in the plasma.

No relationship between low-density lipoproteins and endothelial function in hemodialysis patients

Background: Relationships between low-density lipoprotein cholesterol and endothelial function in hemodialysis patients have yet to be investigated. Furthermore, current reporting of endothelial function data using flow-mediated dilatation has recognised limitations. The aims of the study were to determine the relationship between low-density lipoproteins and endothelial function in hemodialysis patients and to investigate the validity of determining the area under the curve for data collected during the flow-mediated dilatation technique. Methods: Brachial artery responses to reactive hyperemia (endothelial-dependent) and glyceryl trinitrate (endothelial-independent) were assessed in 19 hemodialysis patients using high-resolution ultrasound. Lipid profiles and other factors known to effect brachial artery reactivity were also measured prior to the flow-mediated dilatation technique. Results: There were no significant relationships between serum low-density lipoproteins and endothelial-dependent or -independent vasodilation using absolute change (mm), relative change (%), time to peak change (s) or area under the curve (mm(.)s). In hemodialysis patients with atherosclerosis, area under the curve analysis showed a significantly (p < 0.05) decreased endothelial-dependent response (mean +/- S.D.: 19.2 +/- 17.4) compared to non-atherosclerotic patients (42.3 +/- 28.6). However, when analysing these data using absolute change, relative change or time to peak dilatation, there were no significant differences between the two groups. Conclusions: In summary, there was no relationship between low-density lipoproteins and endothelial function in hemodialysis patients. In addition, area under the curve analysis of flow-mediated vasodilatation data may be a useful method of determining the temporal vascular response during the procedure. (c) 2004 Elsevier Ireland Ltd. All rights reserved.

MULTIPRED: A computational system for prediction of promiscuous HLA binding peptides

MULTIPRED is a web-based computational system for the prediction of peptide binding to multiple molecules ( proteins) belonging to human leukocyte antigens (HLA) class I A2, A3 and class II DR supertypes. It uses hidden Markov models and artificial neural network methods as predictive engines. A novel data representation method enables MULTIPRED to predict peptides that promiscuously bind multiple HLA alleles within one HLA supertype. Extensive testing was performed for validation of the prediction models. Testing results show that MULTIPRED is both sensitive and specific and it has good predictive ability ( area under the receiver operating characteristic curve A(ROC) > 0.80). MULTIPRED can be used for the mapping of promiscuous T-cell epitopes as well as the regions of high concentration of these targets termed T-cell epitope hotspots. MULTIPRED is available at http:// antigen.i2r.a-star.edu.sg/ multipred/.

Relationships of tacrolimus pharmacokinetic measures and adverse outcomes in stable adult liver transplant recipients

Alternative measures to trough concentrations [non-trough concentrations and limited area under the concentration-time curve (AUC)] have been shown to better predict tacrolimus AUC. The aim of this study was to determine if these are also better predictors of adverse outcomes in long term liver transplant recipients. The associations between tacrolimus trough concentrations (C-0), non-trough concentrations (C-1, C-2, C-4, C-6/8), and AUC(0-12) and the occurrence of hypertension, hyperkalaemia, hyperglycaemia and nephrotoxicity were assessed in 34 clinically stable liver transplant patients. The most common adverse outcome was hypertension, prevalence of 36%. Hyperkalaemia and hyperglycaemia had a prevalence of 21% and 13%, respectively. A sequential population pharmacokinetic/pharmacodynamic approach was implemented. No significant association between predicted C-0, C-1, C-2, C-4, C-6/8 or AUC(0-12) and adverse effects could be found. Tacrolimus concentrations and AUC measures were in the same range in patients with and without adverse effects. Measures reported to provide benefit, preventing graft rejection and minimizing acute adverse effects in the early post-transplant period, were not able to predict adverse effects in stable adult liver recipients whose trough concentrations were maintained in the notional target range.

Application and evaluation of classification trees for screening unwanted plants

Risk assessment systems for introduced species are being developed and applied globally, but methods for rigorously evaluating them are still in their infancy. We explore classification and regression tree models as an alternative to the current Australian Weed Risk Assessment system, and demonstrate how the performance of screening tests for unwanted alien species may be quantitatively compared using receiver operating characteristic (ROC) curve analysis. The optimal classification tree model for predicting weediness included just four out of a possible 44 attributes of introduced plants examined, namely: (i) intentional human dispersal of propagules; (ii) evidence of naturalization beyond native range; (iii) evidence of being a weed elsewhere; and (iv) a high level of domestication. Intentional human dispersal of propagules in combination with evidence of naturalization beyond a plants native range led to the strongest prediction of weediness. A high level of domestication in combination with no evidence of naturalization mitigated the likelihood of an introduced plant becoming a weed resulting from intentional human dispersal of propagules. Unlikely intentional human dispersal of propagules combined with no evidence of being a weed elsewhere led to the lowest predicted probability of weediness. The failure to include intrinsic plant attributes in the model suggests that either these attributes are not useful general predictors of weediness, or data and analysis were inadequate to elucidate the underlying relationship(s). This concurs with the historical pessimism that we will ever be able to accurately predict invasive plants. Given the apparent importance of propagule pressure (the number of individuals of an species released), future attempts at evaluating screening model performance for identifying unwanted plants need to account for propagule pressure when collating and/or analysing datasets. The classification tree had a cross-validated sensitivity of 93.6% and specificity of 36.7%. Based on the area under the ROC curve, the performance of the classification tree in correctly classifying plants as weeds or non-weeds was slightly inferior (Area under ROC curve = 0.83 +/- 0.021 (+/- SE)) to that of the current risk assessment system in use (Area under ROC curve = 0.89 +/- 0.018 (+/- SE)), although requires many fewer questions to be answered.

Development of a semimechanistic model to describe the pharmacokinetics of gentamicin in patients receiving Hemodialysis

The aim of this study was to ascertain the most suitable dosing schedule for gentamicin in patients receiving hemodialysis. We developed a model to describe the concentrationtime course of gentamicin in patients receiving hemodialysis. Using the model, an optimal dosing schedule was evaluated. Various dosing regimens were compared in their ability to achieve maximum concentration (C-max, >= 8 mg/L) and area under the concentration time-curve (AUC >= 70 mg(.)h/L and <= 120 mg(.)h/L per 24 hours). The model was evaluated by comparing model predictions against real data collected retrospectively. Simulations from the model confirmed the benefits of predialysis dosing. The mean optimal dose was 230 mg administered immediately before dialysis. The model was found to have good predictive performance when simulated data were compared to data observed in real patients. In summary, a model was developed that describes gentamicin pharmacokinetics in patients receiving hemodialysis. Predialysis dosing provided a superior pharmacokinetic profile than did postdialysis dosing.

Predictive validity of three ActiGraph energy expenditure equations for children

Purpose: This Study evaluated the predictive validity of three previously published ActiGraph energy expenditure (EE) prediction equations developed for children and adolescents. Methods: A total of 45 healthy children and adolescents (mean age: 13.7 +/- 2.6 yr) completed four 5-min activity trials (normal walking. brisk walking, easy running, and fast running) in ail indoor exercise facility. During each trial, participants were all ActiGraph accelerometer oil the right hip. EE was monitored breath by breath using the Cosmed K4b(2) portable indirect calorimetry system. Differences and associations between measured and predicted EE were assessed using dependent t-tests and Pearson correlations, respectively. Classification accuracy was assessed using percent agreement, sensitivity, specificity, and area under the receiver operating characteristic (ROC) curve, Results: None of the equations accurately predicted mean energy expenditure during each of the four activity trials. Each equation, however, accurately predicted mean EE in at least one activity trial. The Puyau equation accurately predicted EE during slow walking. The Trost equation accurately predicted EE during slow running. The Freedson equation accurately predicted EE during fast running. None of the three equations accurately predicted EE during brisk walking. The equations exhibited fair to excellent classification accuracy with respect to activity intensity. with the Trost equation exhibiting the highest classification accuracy and the Puyau equation exhibiting the lowest. Conclusions: These data suggest that the three accelerometer prediction equations do not accurately predict EE on a minute-by-minute basis in children and adolescents during overground walking and running. The equations maybe, however, for estimating participation in moderate and vigorous activity.

Prediction of HLA-DQ3.2 beta ligands: evidence of multiple registers in class II binding peptides

Motivation: While processing of MHC class II antigens for presentation to helper T-cells is essential for normal immune response, it is also implicated in the pathogenesis of autoimmune disorders and hypersensitivity reactions. Sequence-based computational techniques for predicting HLA-DQ binding peptides have encountered limited success, with few prediction techniques developed using three-dimensional models. Methods: We describe a structure-based prediction model for modeling peptide-DQ3.2 beta complexes. We have developed a rapid and accurate protocol for docking candidate peptides into the DQ3.2 beta receptor and a scoring function to discriminate binders from the background. The scoring function was rigorously trained, tested and validated using experimentally verified DQ3.2 beta binding and non-binding peptides obtained from biochemical and functional studies. Results: Our model predicts DQ3.2 beta binding peptides with high accuracy [area under the receiver operating characteristic (ROC) curve A(ROC) > 0.90], compared with experimental data. We investigated the binding patterns of DQ3.2 beta peptides and illustrate that several registers exist within a candidate binding peptide. Further analysis reveals that peptides with multiple registers occur predominantly for high-affinity binders.

Folate supplementation fails to affect vascular function and carotid artery intima media thickness in cyclosporin A-treated renal transplant recipients

Background: Cyclosporin A (CsA)-treated renal transplant recipients (RTR) exhibit relative hyperhomocystinemia and vascular dysfunction. Folate supplementation lowers homocysteine and has been shown to improve vascular function in healthy subjects and patients with coronary artery disease. The aim of this study was to assess the effects of 3 months of folate supplementation (5 mg/day) on vascular function and structure in RTR. Methods: A double-blind, placebo-controlled crossover study was conducted in 10 CsA-treated RTR. Vascular structure was measured as carotid artery intima media thickness (IMT) and function was assessed as changes in brachial artery diameter during reactive hyperemia (RE) and in response to glyceryl trinitrate (GTN). Function data were analyzed as absolute and percent change from baseline and area under the diameter/time curve. Blood samples were collected before and after supplementation and analyzed for total plasma homocysteine, folate, vitamin B-12 and asymmetric dimethyl arginine (ADMA) in addition to regular measures of hemoglobin, hematocrit, mean corpuscular volume (MCV) and serum creatinine. Results: Folate supplementation significantly increased plasma folate by 687% (p < 0.005) and decreased homocysteine by 37% (p < 0.05) with no changes (p > 0.05) in vitamin B 12 or ADMA. There were no significant (p > 0.05) changes in vascular structure or function during the placebo or the folate supplementation phases; IMT; placebo pre mean +/- SD, 0.52 +/- 0.12, post 0.50 +/- 0.11; folate pre 0.55 +/- 0.17, post 0.49 +/- 10.20 mm 5% change in brachial artery diameter (RH, placebo pre 10 +/- 8, post 6 +/- 5; folate pre 9 +/- 7, post 7 +/- 5; GTN, placebo pre 18 +/- 10, post 17 +/- 9, folate pre 16 +/- 9, post-supplementation 18 +/- 8). Conclusion: Three months of folate supplementation decreases plasma homocysteine but has no effect on endothelial function or carotid artery IMT in RTR.