Population pharmacokinetics of clomethiazole and its effect on the natural course of sedation in acute stroke patients

Variability Attribution for Automated Model Building

We investigated the possible advantages of using linearization to evaluate models of residual unexplained variability (RUV) for automated model building in a similar fashion to the recently developed method “residual modeling.” Residual modeling, although fast and easy to automate, cannot identify the impact of implementing the needed RUV model on the imprecision of the rest of model parameters. We used six RUV models to be tested with 12 real data examples. Each example was first linearized; then, we assessed the agreement in improvement of fit between the base model and its extended models for linearization and conventional analysis, in comparison to residual modeling performance. Afterward, we compared the estimates of parameters’ variabilities and their uncertainties obtained by linearization to conventional analysis. Linearization accurately identified and quantified the nature and magnitude of RUV model misspecification similar to residual modeling. In addition, linearization identified the direction of change and quantified the magnitude of this change in variability parameters and their uncertainties. This method is implemented in the software package PsN for automated model building/evaluation with continuous data.

Gamma aminobutyric acid (GABA) receptor agonists for acute stroke

BACKGROUND

Gamma aminobutyric acid (GABA) receptor agonists have been shown to have a neuroprotectant effect in reducing infarct size and improving functional outcome in animal models of cerebrovascular disease. However, the sedative effects of GABA receptor agonists have limited their wider application in people with acute stroke, due to the potential risk of stupor. This is an update of a Cochrane Review first published in 2013, and previously updated in 2014 and 2016.

OBJECTIVES

To determine the efficacy and safety of GABA receptor agonists in the treatment of acute stroke.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register (accessed May 2018), the Cochrane Central Register of Controlled Trials (CENTRAL) 2018, Issue 4 (accessed May 2018), MEDLINE (from 1949 to May 2018), Embase (from 1980 to May 2018), CINAHL (from 1982 to May 2018), AMED (from 1985 to May 2018), and 11 Chinese databases (accessed May 2018). In an effort to identify further published, unpublished, and ongoing trials we searched ongoing trial registers, reference lists, and relevant conference proceedings, and contacted authors and pharmaceutical companies.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) investigating GABA receptor agonists versus placebo for people with acute stroke (within 12 hours after stroke onset), with the primary outcomes of efficacy and safety.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the titles and abstracts of identified records, selected studies for inclusion, extracted eligible data, cross-checked the data for accuracy, and assessed the risk of bias. We used the GRADE approach to assess the quality of the evidence.

MAIN RESULTS

We included five trials with 3838 participants (acute ischemic or hemorrhagic stroke patients, 3758 analyzed). Most of the participants recruited had acute ischaemic stroke, with limited data available from participants with other stroke subtypes, including total anterior circulation syndrome (TACS). The methodological quality of the included trials was generally good, with an unclear risk for selection bias only. For death and dependency at three months, pooled results did not find a significant difference for chlormethiazole versus placebo (risk ratio (RR) 1.03, 95% confidence interval (CI) 0.96 to 1.11; four trials; 2909 participants; moderate-quality evidence) and for diazepam versus placebo (RR 0.94, 95% CI 0.82 to 1.07; one trial; 849 participants; moderate-quality evidence). The most frequent adverse events related to chlormethiazole were somnolence (RR 4.56, 95% CI 3.50 to 5.95; two trials; 2527 participants; moderate-quality evidence) and rhinitis (RR 4.75, 95% CI 2.67 to 8.46; two trials; 2527 participants; moderate-quality evidence).

AUTHORS' CONCLUSIONS

This review provides moderate-quality evidence that fails to support the use of GABA receptor agonists (chlormethiazole or diazepam) for the treatment of people with acute stroke. More well-designed RCTs with large samples of participants with total anterior circulation syndrome are required to determine if there are benefits for this subgroup. Somnolence and rhinitis are frequent adverse events related to chlormethiazole.

Model-Based Residual Post-Processing for Residual Model Identification

The purpose of this study was to investigate if model-based post-processing of common diagnostics can be used as a diagnostic tool to quantitatively identify model misspecifications and rectifying actions. The main investigated diagnostic is conditional weighted residuals (CWRES). We have selected to showcase this principle with residual unexplained variability (RUV) models, where the new diagnostic tool is used to scan extended RUV models and assess in a fast and robust way whether, and what, extensions are expected to provide a superior description of data. The extended RUV models evaluated were autocorrelated errors, dynamic transform both sides, inter-individual variability on RUV, power error model, t-distributed errors, and time-varying error magnitude. The agreement in improvement in goodness-of-fit between implementing these extended RUV models on the original model and implementing these extended RUV models on CWRES was evaluated in real and simulated data examples. Real data exercise was applied to three other diagnostics: conditional weighted residuals with interaction (CWRESI), individual weighted residuals (IWRES), and normalized prediction distribution errors (NPDE). CWRES modeling typically predicted (i) the nature of model misspecifications, (ii) the magnitude of the expected improvement in fit in terms of difference in objective function value (ΔOFV), and (iii) the parameter estimates associated with the model extension. Alternative metrics (CWRESI, IWRES, and NPDE) also provided valuable information, but with a lower predictive performance of ΔOFV compared to CWRES. This method is a fast and easily automated diagnostic tool for RUV model development/evaluation process; it is already implemented in the software package PsN.

Crowdsourced Asparagus Urinary Odor Population Kinetics

The consumption of asparagus is associated with the production of malodorous urine with considerable interindividual variability (IIV). To characterize the urinary odor kinetics after consumption of asparagus spears, we conducted a study with consenting attendees from two American Society for Clinical Pharmacology and Therapeutics (ASCPT) meetings. Subjects were randomized to eat a specific number of asparagus spears, and then asked to report their urinary odor perception. Eighty‐seven subjects were included in the final analysis. A mixed effect proportional odds model was developed that adequately characterized the dose‐response relationship. We estimated the half‐life of the asparagus effect on malodorous urine to be 4.7 hours (relative standard error (RSE) = 13.2%), and identified a dose‐response slope term with good precision (24.3%). Age was found as the predictor of IIV in slope estimates. This study design and tools can be used as a demonstration “crowdsourcing” project for studying population kinetics in organizational and educational settings.

A Minimal Continuous-Time Markov Pharmacometric Model

In this work, an alternative model to discrete-time Markov model (DTMM) or standard continuous-time Markov model (CTMM) for analyzing ordered categorical data with Markov properties is presented: the minimal CTMM (mCTMM). Through a CTMM reparameterization and under the assumption that the transition rate between two consecutive states is independent on the state, the Markov property is expressed through a single parameter, the mean equilibration time, and the steady-state probabilities are described by a proportional odds (PO) model. The mCTMM performance was evaluated and compared to the PO model (ignoring Markov features) and to published Markov models using three real data examples: the four-state fatigue and hand-foot syndrome data in cancer patients initially described by DTMM and the 11-state Likert pain score data in diabetic patients previously analyzed with a count model including Markovian transition probability inflation. The mCTMM better described the data than the PO model, and adequately predicted the average number of transitions per patient and the maximum achieved scores in all examples. As expected, mCTMM could not describe the data as well as more flexible DTMM but required fewer estimated parameters. The mCTMM better fitted Likert data than the count model. The mCTMM enables to explore the effect of potential predictive factors such as drug exposure and covariates, on ordered categorical data, while accounting for Markov features, in cases where DTMM and/or standard CTMM is not applicable or conveniently implemented, e.g., non-uniform time intervals between observations or large number of categories.

Gamma aminobutyric acid (GABA) receptor agonists for acute stroke

BACKGROUND

Gamma aminobutyric acid (GABA) receptor agonists have been shown to have a neuroprotectant effect in reducing infarct size and improving functional outcome in animal models of cerebrovascular disease. However, the sedative effects of GABA receptor agonists have limited their wider application in people with acute stroke, due to the potential risk of stupor. This is an update of a Cochrane review first published in 2013, and previously updated in 2014.

OBJECTIVES

To determine the efficacy and safety of GABA receptor agonists in the treatment of acute stroke.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register (accessed March 2016), the Cochrane Central Register of Controlled Trials (CENTRAL) 2016, Issue 3, part of the Cochrane Library (accessed March 2016), MEDLINE (from 1949 to March 2016), Embase (from 1980 to March 2016), CINAHL (from 1982 to March 2016), AMED (from 1985 to March 2016), and 11 Chinese databases (accessed March 2016). In an effort to identify further published, unpublished, and ongoing trials we searched ongoing trials registers, reference lists, and relevant conference proceedings, and contacted authors and pharmaceutical companies.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) investigating GABA receptor agonists versus placebo for people with acute stroke (within 12 hours after stroke onset), with the primary outcomes of efficacy and safety.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the titles and abstracts of identified records, selected studies for inclusion, extracted eligible data, cross-checked the data for accuracy, and assessed the risk of bias.

MAIN RESULTS

We included five trials with 3838 participants (3758 analyzed). The methodological quality of the included trials was generally good, with an unclear risk for selection bias only. Four trials (N = 2909) measured death and dependency at three months for chlormethiazole versus placebo; pooled results did not find a significant difference (risk ratio (RR) 1.03, 95% confidence interval (CI) 0.96 to 1.11). One trial (N = 849) measured this outcome for diazepam versus placebo (RR 0.94, 95% CI 0.82 to 1.07). The most frequent adverse events related to chlormethiazole were somnolence (RR 4.56, 95% CI 3.50 to 5.95; two trials; N = 2527) and rhinitis (RR 4.75, 95% CI 2.67 to 8.46; two trials; N = 2527).

AUTHORS' CONCLUSIONS

This review provides moderate-quality evidence that fails to support the use of GABA receptor agonists (chlormethiazole or diazepam) for the treatment of people with acute stroke. More well-designed RCTs with large samples of participants with total anterior circulation syndrome are required to determine if there are benefits for this subgroup. Somnolence and rhinitis are frequent adverse events related to chlormethiazole.

Selective Time- and NADPH-Dependent Inhibition of Human CYP2E1 by Clomethiazole

The sedative clomethiazole (CMZ) has been used in Europe since the mid-1960s to treat insomnia and alcoholism. It has been previously demonstrated in clinical studies to reversibly inhibit human CYP2E1 in vitro and decrease CYP2E1-mediated elimination of chlorzoxazone. We have investigated the selectivity of CMZ inhibition of CYP2E1 in pooled human liver microsomes (HLMs). In a reversible inhibition assay of the major drug-metabolizing cytochrome P450 (P450) isoforms, CYP2A6 and CYP2E1 exhibited IC50 values of 24 µM and 42 µM, respectively with all other isoforms exhibiting values >300 µM. When CMZ was preincubated with NADPH and liver microsomal protein for 30 minutes before being combined with probe substrates, however, more potent inhibition was observed for CYP2E1 and CYP2B6 but not CYP2A6 or other P450 isoforms. The substantial increase in potency of CYP2E1 inhibition upon preincubation enables the use of CMZ to investigate the role of human CYP2E1 in xenobiotic metabolism and provides advantages over other chemical inhibitors of CYP2E1. The KI and kinact values obtained with HLM-catalyzed 6-hydroxylation of chlorzoxazone were 40 µM and 0.35 minute(-1), respectively, and similar to values obtained with recombinant CYP2E1 (41 µM, 0.32 minute(-1)). The KI and kinact values, along with other parameters, were used in a mechanistic static model to explain earlier observations of a profound decrease in the rate of chlorzoxazone elimination in volunteers despite the absence of detectable CMZ in blood.

Methods and strategies for assessing uncontrolled drug-drug interactions in population pharmacokinetic analyses: results from the International Society of Pharmacometrics (ISOP) Working Group

The purpose of this work was to present a consolidated set of guidelines for the analysis of uncontrolled concomitant medications (ConMed) as a covariate and potential perpetrator in population pharmacokinetic (PopPK) analyses. This white paper is the result of an industry-academia-regulatory collaboration. It is the recommendation of the working group that greater focus be given to the analysis of uncontrolled ConMeds as part of a PopPK analysis of Phase 2/3 data to ensure that the resulting outcome in the PopPK analysis can be viewed as reliable. Other recommendations include: (1) collection of start and stop date and clock time, as well as dose and frequency, in Case Report Forms regarding ConMed administration schedule; (2) prespecification of goals and the methods of analysis, (3) consideration of alternate models, other than the binary covariate model, that might more fully characterize the interaction between perpetrator and victim drug, (4) analysts should consider whether the sample size, not the percent of subjects taking a ConMed, is sufficient to detect a ConMed effect if one is present and to consider the correlation with other covariates when the analysis is conducted, (5) grouping of ConMeds should be based on mechanism (e.g., PGP-inhibitor) and not drug class (e.g., beta-blocker), and (6) when reporting the results in a publication, all details related to the ConMed analysis should be presented allowing the reader to understand the methods and be able to appropriately interpret the results.

Gamma aminobutyric acid (GABA) receptor agonists for acute stroke

BACKGROUND

Gamma aminobutyric acid (GABA) receptor agonists have been shown to have a neuroprotectant effect in reducing infarct size and improving functional outcome in animal models of cerebral ischemia. However, the sedation effects of GABA receptor agonists have limited their wider application in acute stroke patients due to the potential risk of stupor.

OBJECTIVES

To determine the efficacy and safety of GABA receptor agonists in the treatment of acute stroke.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register (February 2014), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2014, Issue 5), MEDLINE (1949 to June 2014), EMBASE (1980 to June 2014), CINAHL (1982 to June 2014), AMED (1985 to June 2014) and 11 Chinese databases (June 2014). In an effort to identify further published, unpublished and ongoing trials we searched ongoing trials registers, reference lists and relevant conference proceedings, and contacted authors and pharmaceutical companies.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) investigating GABA receptor agonists versus placebo for acute stroke patients (within 12 hours after stroke onset), with the outcomes of death or dependency, functional independence and adverse events.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the titles and abstracts of identified records, selected studies for inclusion, extracted eligible data, cross-checked the data for accuracy and assessed the methodological quality.

MAIN RESULTS

We included five trials with 3838 patients. The methodological quality of the included trials was generally good, with low risk of bias. Four trials measured death and dependency at three months in chlormethiazole versus placebo without significant difference (risk ratio (RR) 1.03, 95% confidence interval (CI) 0.95 to 1.11). One trial measured this outcome between diazepam and placebo (RR 0.94, 95% CI 0.82 to 1.07). In the subgroup analysis of total anterior circulation syndrome (TACS), a higher percentage of functional independence was found in the chlormethiazole group (RR 1.33, 95% CI 1.09 to 1.64). The frequent adverse events related to chlormethiazole were somnolence (RR 4.56, 95% CI 3.50 to 5.95) and rhinitis (RR 4.75, 95% CI 2.67 to 8.46).

AUTHORS' CONCLUSIONS

This review does not provide the evidence to support the use of GABA receptor agonists (chlormethiazole or diazepam) for the treatment of patients with acute ischemic or hemorrhagic stroke. Chlormethiazole appeared to be beneficial in improving functional independence in patients with TACS according to the subgroup analysis, but this result must be interpreted with great caution. More well-designed RCTs with large samples of TACS would be required for further confirmation. However, somnolence and rhinitis are frequent adverse events related to chlormethiazole.

Gamma aminobutyric acid (GABA) receptor agonists for acute stroke

BACKGROUND

Gamma aminobutyric acid (GABA) receptor agonists have been shown to have a neuroprotectant effect in reducing infarct size and improving functional outcome in animal models of cerebral ischemia. However, the sedation effects of GABA receptor agonists have limited their wider application in acute stroke patients due to the potential risk of stupor.

OBJECTIVES

To determine the efficacy and safety of GABA receptor agonists in the treatment of acute stroke.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register (January 2012), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2012, Issue 1), MEDLINE (1949 to March 2012), EMBASE (1980 to March 2012), CINAHL (1982 to March 2012), AMED (1985 to March 2012) and 11 Chinese databases (March 2012). In an effort to identify further published, unpublished and ongoing trials we searched ongoing trials registers, reference lists and relevant conference proceedings, and contacted authors and pharmaceutical companies.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) investigating GABA receptor agonists versus placebo for acute stroke patients (within 12 hours after stroke onset), with the outcomes of death or dependency, functional independence and adverse events.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the titles and abstracts of identified records, selected studies for inclusion, extracted eligible data, cross-checked the data for accuracy and assessed the methodological quality.

MAIN RESULTS

We included five trials with 3838 patients. The methodological quality of the included trials was generally good, with low risk of bias. Four trials measured death and dependency at three months in chlormethiazole versus placebo without significant difference (risk ratio (RR) 1.03, 95% confidence interval (CI) 0.95 to 1.11). One trial measured this outcome between diazepam and placebo (RR 0.94, 95% CI 0.82 to 1.07). In the subgroup analysis of total anterior circulation syndrome (TACS), a higher percentage of functional independence was found in the chlormethiazole group (RR 1.33, 95% CI 1.09 to 1.64). The frequent adverse events related to chlormethiazole were somnolence (RR 4.56, 95% CI 3.50 to 5.95) and rhinitis (RR 4.75, 95% CI 2.67 to 8.46).

AUTHORS' CONCLUSIONS

This review does not provide the evidence to support the use of GABA receptor agonists (chlormethiazole or diazepam) for the treatment of patients with acute ischemic or hemorrhagic stroke. Chlormethiazole appeared to be beneficial in improving functional independence in patients with TACS according to the subgroup analysis, but this result must be interpreted with great caution. More well-designed RCTs with large samples of TACS would be required for further confirmation. However, somnolence and rhinitis are frequent adverse events related to chlormethiazole.

Guidelines for the early management of patients with acute ischemic stroke: a guideline for healthcare professionals from the American Heart Association/American Stroke Association

BACKGROUND AND PURPOSE

The authors present an overview of the current evidence and management recommendations for evaluation and treatment of adults with acute ischemic stroke. The intended audiences are prehospital care providers, physicians, allied health professionals, and hospital administrators responsible for the care of acute ischemic stroke patients within the first 48 hours from stroke onset. These guidelines supersede the prior 2007 guidelines and 2009 updates.

METHODS

Members of the writing committee were appointed by the American Stroke Association Stroke Council's Scientific Statement Oversight Committee, representing various areas of medical expertise. Strict adherence to the American Heart Association conflict of interest policy was maintained throughout the consensus process. Panel members were assigned topics relevant to their areas of expertise, reviewed the stroke literature with emphasis on publications since the prior guidelines, and drafted recommendations in accordance with the American Heart Association Stroke Council's Level of Evidence grading algorithm.

RESULTS

The goal of these guidelines is to limit the morbidity and mortality associated with stroke. The guidelines support the overarching concept of stroke systems of care and detail aspects of stroke care from patient recognition; emergency medical services activation, transport, and triage; through the initial hours in the emergency department and stroke unit. The guideline discusses early stroke evaluation and general medical care, as well as ischemic stroke, specific interventions such as reperfusion strategies, and general physiological optimization for cerebral resuscitation.

CONCLUSIONS

Because many of the recommendations are based on limited data, additional research on treatment of acute ischemic stroke remains urgently needed.

Therapeutic drug monitoring for drugs used in the treatment of substance-related disorders: literature review using a therapeutic drug monitoring appropriateness rating scale

BACKGROUND

The efficacy of drugs for the treatment of substance-related disorders is moderate at best. Therapeutic drug monitoring (TDM) could be an instrument to improve outcomes. Because TDM for most of those drugs is not established, the authors reviewed the literature and built a rating scale to detect the potential added value of TDM for these pharmacologic agents.

METHODS

A literature search was performed for acamprosate, bupropion, buprenorphine, clomethiazole, disulfiram, methadone, naltrexone, and varenicline. The rating scale included 22 items and was divided in five categories: efficacy, toxicity, pharmacokinetics, patient characteristics, and cost-effectiveness. Three reference substances with established TDM were similarly assessed for comparison: clozapine, lithium, and nortriptyline. The three reference substances achieved scores of 15, 12, and 14 points, respectively.

RESULTS

Drugs for treatment of substance-related disorders achieved 3 to 17 points, 17 for methadone, 11 for buprenorphine, 10 for disulfiram, also 10 for naltrexone for the indication opioid-dependence and 9 for the indication alcohol dependence as well as bupropion, 7 points for acamprosate, 6 points for clomethiazole, and 3 for varenicline.

CONCLUSIONS

It is concluded that systematic evaluation of drug- and patient-related variables with the new rating scale can estimate the appropriateness of TDM. Because their rating revealed similar scores as the three reference drugs, it is proposed that TDM should be established for bupropion, buprenorphine, disulfiram or a metabolite, methadone, and naltrexone. An objective rating of drug- and patient-related characteristics could help laboratories focus their method development on the most likely drugs to require TDM along with a thorough drug use evaluation.

Implementation and evaluation of the SAEM algorithm for longitudinal ordered categorical data with an illustration in pharmacokinetics-pharmacodynamics

Analysis of longitudinal ordered categorical efficacy or safety data in clinical trials using mixed models is increasingly performed. However, algorithms available for maximum likelihood estimation using an approximation of the likelihood integral, including LAPLACE approach, may give rise to biased parameter estimates. The SAEM algorithm is an efficient and powerful tool in the analysis of continuous/count mixed models. The aim of this study was to implement and investigate the performance of the SAEM algorithm for longitudinal categorical data. The SAEM algorithm is extended for parameter estimation in ordered categorical mixed models together with an estimation of the Fisher information matrix and the likelihood. We used Monte Carlo simulations using previously published scenarios evaluated with NONMEM. Accuracy and precision in parameter estimation and standard error estimates were assessed in terms of relative bias and root mean square error. This algorithm was illustrated on the simultaneous analysis of pharmacokinetic and discretized efficacy data obtained after a single dose of warfarin in healthy volunteers. The new SAEM algorithm is implemented in MONOLIX 3.1 for discrete mixed models. The analyses show that for parameter estimation, the relative bias is low for both fixed effects and variance components in all models studied. Estimated and empirical standard errors are similar. The warfarin example illustrates how simple and rapid it is to analyze simultaneously continuous and discrete data with MONOLIX 3.1. The SAEM algorithm is extended for analysis of longitudinal categorical data. It provides accurate estimates parameters and standard errors. The estimation is fast and stable.

Modeling subpopulations with the $MIXTURE subroutine in NONMEM: finding the individual probability of belonging to a subpopulation for the use in model analysis and improved decision making

In nonlinear mixed effects modeling using NONMEM, mixture models can be used for multimodal distributions of parameters. The fraction of individuals belonging to each of the subpopulations can be estimated, and the most probable subpopulation for each patient is output (MIXEST(k)). The objective function value (OFV) that is minimized is the sum of the OFVs for each patient (OFV(i)), which in turn is the sum across the k subpopulations (OFV(i,k)). The OFV(i,k) values can be used together with the total probability in the population of belonging to subpopulation k to calculate the individual probability of belonging to the subpopulation (IP(k)). Our objective was to explore the information gained by using IP(k) instead of or in addition to MIXEST(k) in the analysis of mixture models. Two real data sets described previously by mixture models as well as simulations were used to explore the use of IP(k) and the precision of individual parameter values based on IP(k) and MIXEST(k). For both real data-based mixture models, a substantial fraction (11% and 26%) of the patients had IP(k) values not close to 0 or 1 (IP(k) between 0.25 and 0.75). Simulations of eight different scenarios showed that individual parameter estimates based on MIXEST were less precise than those based on IP(k), as the root mean squared error was reduced for IP(k) in all scenarios. A probability estimate such as IP(k) provides more detailed information about each individual than the discrete MIXEST(k). Individual parameter estimates based on IP(k) should be preferable whenever individual parameter estimates are to be used as study output or for simulations.

Exposure-effect population model of inolimomab, a monoclonal antibody administered in first-line treatment for acute graft-versus-host disease

BACKGROUND AND OBJECTIVE

Inolimomab, a monoclonal antibody against interleukin (IL)-2Ralpha (CD25) has shown promising results in the treatment of corticosteroid-resistant acute graft-versus-host disease (GvHD). The objective of the present study was to characterise the pharmacokinetic and pharmacodynamic properties of inolimomab as first-line treatment in this condition.

METHODS

The data came from 21 patients with acute GvHD (8 with an International Bone Marrow Transplant Registry [IBMTR] score of B, 11 with a score of C and 2 with a score of D) following haematopoietic stem cell transplantation after a median delay of 26 days (range 10-127 days). Inolimomab was administered at 0.1, 0.2, 0.3 or 0.4 mg/kg daily in association with methylprednisolone (2 mg/kg) for 8 or 16 days depending on the status at day 9. Then, for responder patients, administrations were continued three times weekly until day 28. Inolimomab concentrations and pharmacodynamic data (acute GvHD scores) were recorded during the study. The pharmacodynamic data were assessed in four grades according to the IBMTR and Glucksberg classification in parallel with Karnofsky scores. A population analysis was developed using a nonlinear mixed-effects model to define the pharmacokinetic model, to test covariates and, when apparent, to model the exposure-effect relationship by a proportional odds model. The modelling was finally qualified by a predictive check.

RESULTS

The best pharmacokinetic model was two-compartmental. For each score, the most demonstrative exposure-effect graphics linked the cumulative area under the concentration-time curve to cumulated probabilities of observing a specific score. This relationship was identified as a maximum effect model for the skin (with two patient subpopulations: sensitive/less sensitive) and a linear model for the intestinal tract and liver. No covariate was identified as influencing any of these parameters.

CONCLUSION

Inolimomab exposure-effect relationships as first-line treatment for acute GvHD have been identified and modelled. The discovered dose-effect relationship allows confirmation of the treatment response, thereby establishing the first step towards optimising the inolimomab dosage in future trials.

The lasso--a novel method for predictive covariate model building in nonlinear mixed effects models

Covariate models for population pharmacokinetics and pharmacodynamics are often built with a stepwise covariate modelling procedure (SCM). When analysing a small dataset this method may produce a covariate model that suffers from selection bias and poor predictive performance. The lasso is a method suggested to remedy these problems. It may also be faster than SCM and provide a validation of the covariate model. The aim of this study was to implement the lasso for covariate selection within NONMEM and to compare this method to SCM. In the lasso all covariates must be standardised to have zero mean and standard deviation one. Subsequently, the model containing all potential covariate-parameter relations is fitted with a restriction: the sum of the absolute covariate coefficients must be smaller than a value, t. The restriction will force some coefficients towards zero while the others are estimated with shrinkage. This means in practice that when fitting the model the covariate relations are tested for inclusion at the same time as the included relations are estimated. For a given SCM analysis, the model size depends on the P-value required for selection. In the lasso the model size instead depends on the value of t which can be estimated using cross-validation. The lasso was implemented as an automated tool using PsN. The method was compared to SCM in 16 scenarios with different dataset sizes, number of investigated covariates and starting models for the covariate analysis. Hundred replicate datasets were created by resampling from a PK-dataset consisting of 721 stroke patients. The two methods were compared primarily on the ability to predict external data, estimate their own predictive performance (external validation), and on the computer run-time. In all 16 scenarios the lasso predicted external data better than SCM with any of the studied P-values (5%, 1% and 0.1%), but the benefit was negligible for large datasets. The lasso cross-validation provided a precise and nearly unbiased estimate of the actual prediction error. On a single processor, the lasso was faster than SCM. Further, the lasso could run completely in parallel whereas SCM must run in steps. In conclusion, the lasso is superior to SCM in obtaining a predictive covariate model on a small dataset or on small subgroups (e.g. rare genotype). Run in parallel the lasso could be much faster than SCM. Using cross-validation, the lasso provides a validation of the covariate model and does not require the user to specify a P-value for selection.

Guidelines for the Early Management of Adults With Ischemic Stroke

Purpose— Our goal is to provide an overview of the current evidence about components of the evaluation and treatment of adults with acute ischemic stroke. The intended audience is physicians and other emergency healthcare providers who treat patients within the first 48 hours after stroke. In addition, information for healthcare policy makers is included.

Methods— Members of the panel were appointed by the American Heart Association Stroke Council’s Scientific Statement Oversight Committee and represented different areas of expertise. The panel reviewed the relevant literature with an emphasis on reports published since 2003 and used the American Heart Association Stroke Council’s Levels of Evidence grading algorithm to rate the evidence and to make recommendations. After approval of the statement by the panel, it underwent peer review and approval by the American Heart Association Science Advisory and Coordinating Committee. It is intended that this guideline be fully updated in 3 years.

Results— Management of patients with acute ischemic stroke remains multifaceted and includes several aspects of care that have not been tested in clinical trials. This statement includes recommendations for management from the first contact by emergency medical services personnel through initial admission to the hospital. Intravenous administration of recombinant tissue plasminogen activator remains the most beneficial proven intervention for emergency treatment of stroke. Several interventions, including intra-arterial administration of thrombolytic agents and mechanical interventions, show promise. Because many of the recommendations are based on limited data, additional research on treatment of acute ischemic stroke is needed.

Guidelines for the early management of adults with ischemic stroke: a guideline from the American Heart Association/American Stroke Association Stroke Council, Clinical Cardiology Council, Cardiovascular Radiology and Intervention Council, and the Atherosclerotic Peripheral Vascular Disease and Quality of Care Outcomes in Research Interdisciplinary Working Groups: the American Academy of Neurology affirms the value of this guideline as an educational tool for neurologists

PURPOSE

Our goal is to provide an overview of the current evidence about components of the evaluation and treatment of adults with acute ischemic stroke. The intended audience is physicians and other emergency healthcare providers who treat patients within the first 48 hours after stroke. In addition, information for healthcare policy makers is included.

METHODS

Members of the panel were appointed by the American Heart Association Stroke Council's Scientific Statement Oversight Committee and represented different areas of expertise. The panel reviewed the relevant literature with an emphasis on reports published since 2003 and used the American Heart Association Stroke Council's Levels of Evidence grading algorithm to rate the evidence and to make recommendations. After approval of the statement by the panel, it underwent peer review and approval by the American Heart Association Science Advisory and Coordinating Committee. It is intended that this guideline be fully updated in 3 years.

RESULTS

Management of patients with acute ischemic stroke remains multifaceted and includes several aspects of care that have not been tested in clinical trials. This statement includes recommendations for management from the first contact by emergency medical services personnel through initial admission to the hospital. Intravenous administration of recombinant tissue plasminogen activator remains the most beneficial proven intervention for emergency treatment of stroke. Several interventions, including intra-arterial administration of thrombolytic agents and mechanical interventions, show promise. Because many of the recommendations are based on limited data, additional research on treatment of acute ischemic stroke is needed.

Modelling a spontaneously reported side effect by use of a Markov mixed-effects model

AIMS

To present a method for analyzing side-effect data where change in severity is spontaneously reported during the experiment.

METHODS

A clinical study in 12 healthy volunteers aimed to investigate the concentration-response characteristics of a CNS-specific side-effect was conducted. After an open session where the subjects experienced the side-effect and where the individual pharmacokinetic parameters were evaluated they were randomized to a sequence of three different infusion rates of the drug in a double-blinded crossover way. The infusion rates were individualized to achieve the same target concentration in all subjects and different drug input rates were selected to mimic absorption profiles from different formulations. The occurrence of the specific side-effect and any subsequent change in severity was self-reported by the subjects. Severity was recorded as 0 = no side-effect, 1 = mild side-effect and 2 = moderate or severe side-effect.

RESULTS

The side-effect data were analyzed using a mixed-effects model for ordered categorical data with and without Markov elements. The former model estimated the probability of having a certain side-effect score conditioned on the preceding observation and drug exposure. The observed numbers of transitions between scores were from 0 -> 1: 24, from 0- > 2: 11, from 1 - >, 2: 23, from 2- > 1: 1, from 2- > 0: 32 and from 1 - >0: 2. The side-effect model consisted of an effect-compartment model with a tolerance compartment. The predictive performance of the Markov model was investigated by a posterior predictive check (PPC), where 100 datasets were simulated from the final model. Average number of the different transitions from the PPC was from 0 - > 1: 26, from 0 - > 2: 11, from 1 - > 2: 25, from 2 - >1: 1, from 2 - >0: 35 and from 1 - > 0: 1. A similar PPC for the model without Markov elements was at considerable disparity with the data.

CONCLUSION

This approach of incorporating Markov elements in an analysis of spontaneously reported categorical side-effect data could adequately predict the observed side-effect time course and could be considered in analyses of categorical data where dependence between observations is an issue.

The pharmacology of chlormethiazole: a potential neuroprotective agent?

Chlormethiazole is a thiazole derivative with a long history of use as a sedative agent. The mode of action of the drug has been partly worked out and has been established with recognition that its mechanism of action involves potentiation of GABA activity, the major intrinsic inhibitory neurotransmitter. Animal models of stroke ranging from rodents to primates have suggested an optimistic role for chlormethiazole in preventing both anatomical and functional deleterious effects of stroke. Phase III clinical trials, therefore, proceeded but unfortunately with very little success. Recently, the animal models have been revisited in an attempt to identify causes for this discrepancy between the results from preclinical and clinical studies. This review studies the pharmacological roots of chlormethiazole from its origin through to its licensed and novel applications. Emphasis is placed on discussing the animal experiments which led to its grooming as a neuroprotective agent and also on the human trials. The review seeks to explain the discrepancies between animal and human studies, which include short survival times of experimental subjects, speed of drug administration and fundamental differences between species. The primate model of stroke perhaps offers the nearest alternative to phase III trials and has recently been used to compare a number of newer neuroprotective agents with greater efficacy than chlormethiazole. In addition, novel approaches involving human neurochemical analyses in vivo are described which may help bridge the gap between animal models and future phase III trials.