Shortening of the electromechanical window in the ketamine/xylazine-anesthetized guinea pig model to assess pro-arrhythmic risk in early drug development.

BACKGROUND: A negative electromechanical window (EMw) was recently proposed as a better preclinical tool than QTc interval to predict clinical pro-arrhythmic potential. As such, we utilized the ketamine/xylazine anesthetized guinea pig to characterize the EMw and QTc interval for a diverse set of reference agents with known clinical pro-arrhythmic potential. Then we determined the clinical proarrhythmia predictive capacity of EMw shortening compared to hERG inhibition or QTc interval prolongation alone. METHODS: Changes in EMw and QTc interval by 26 reference agents were evaluated in the ketamine/xylazine-anesthetized guinea pig. Confusion matrix analysis using the hERG, QTc and EMw indexes (hERG IC50, QTc EC5 or the EMw EC-10 divided by their respective free therapeutic maximal plasma concentration) at various folds the therapeutic concentrations was conducted to assess the concordance of each index to predict clinical pro-arrhythmic risk. RESULTS: Shortening of the EMw concomitant to an increase in QTc interval was observed in the GP with known pro-arrhythmic drugs. Non-torsadogenic compounds did not cause EMw shortening, although some prolonged the QTc interval. The preclinical:clinical concordance of the EMw index (88%) was similar (p>0.05) to using QTc interval prolongation alone (85%) but significantly greater (p<0.05) than using hERG inhibition alone (69%). In addition, the specificity when using the EMw (87%) was largely greater (p<0.05) than using QTc interval (73%) or hERG inhibition (60%) alone. When the components of the response (duration of left ventricular pressure (LVP) cycle (QLVPend) or QT interval) that caused EMw shortening were considered, the concordance is further improved (>95%). CONCLUSION: EMw shortening improves QTc interval prolongation recording in early drug development and increases the translatability over existing preclinical tools in predicting clinical arrhythmias.

Inter-study variability of preclinical in vivo safety studies and translational exposure-QTc relationships--a PKPD meta-analysis.

BACKGROUND AND PURPOSE: Preclinical cardiovascular safety studies (CVS) have been compared between facilities with respect to their sensitivity to detect drug-induced QTc prolongation (ΔQTc). Little is known about the consistency of quantitative ΔQTc predictions that are relevant for translation to humans. EXPERIMENTAL APPROACH: We derived typical ΔQTc predictions at therapeutic exposure (ΔQTcTHER ) with 95% confidence intervals (95%CI) for 3 Kv 11.1 (hERG) channel blockers (moxifloxacin, dofetilide and sotalol) from a total of 14 CVS with variable designs in the conscious dog. Population pharmacokinetic-pharmacodynamic (PKPD) analysis of each study was followed by a meta-analysis (pooling 2-6 studies including 10-32 dogs per compound) to derive meta-predictions of typical ΔQTcTHER . Meta-predictions were used as a reference to evaluate the consistency of study predictions and to relate results to those found in the clinical literature. KEY RESULTS: The 95%CIs of study-predicted ΔQTcTHER comprised in 13 out of 14 cases the meta-prediction. Overall inter-study variability (mean deviation from meta-prediction at upper level of therapeutic exposure) was 30% (range: 1-69%). Meta-ΔQTcTHER predictions for moxifloxacin, dofetilide and sotalol overlapped with reported clinical QTc prolongation when expressed as %-prolongation from baseline. CONCLUSIONS AND IMPLICATIONS: Consistent exposure-ΔQTc predictions were obtained from single preclinical dog studies of highly variable designs by systematic PKPD analysis, which is suitable for translational purposes. The good preclinical-clinical pharmacodynamic correlations obtained suggest that such an analysis should be more routinely applied to increase the informative and predictive value of results obtained from animal experiments.

In vivo higher glucuronidation of mycophenolic acid in male than in female recipients of a cadaveric kidney allograft and under immunosuppressive therapy with mycophenolate mofetil.

Mycophenolate mofetil (MMF), an immunosuppressant drug used in organ transplantation to prevent rejection, is being used increasingly in association with cyclosporine and tacrolimus. Mycophenolic acid (MPA) is primarily metabolized in the liver to its 7-O-glucuronide (MPAG) derivative. The concentrations of MPAG in serum are many times the concentrations of MPA. Although MPAG has not shown immunosuppressant activity, it was postulated that it could displace MPA from its binding sites on albumin and hence increase the biologic effects of MPA. This effect could be important for patients with acute renal failure; under this condition, MPAG was shown to accumulate. The goal of this study was to document the MPAG/MPA concentration ratio in 100 renal transplant patients under a mixed immunosuppressive therapy. Further, the study addressed the question of whether MPAG can displace MPA in vivo from bound albumin in a representative renal transplant patient population under immunosuppressive therapy. Levels of MPAG and MPA were measured by high-performance liquid chromatography. The distribution of the ratios was not parametric as it tailed toward elevated values. After a square root transformation of the data, parametric analysis was possible. The average MPAG/MPA ratio was 15.0 +/- 2.2 for men versus 7.7 +/- 0.9 for women. Men treated with MMF and tacrolimus showed a lower ratio than patients treated with MMF and cyclosporine, confirming that tacrolimus inhibits glucuronidation of MPA. Further, it was determined that at physiologic concentrations, MPAG does not increase the amount of free MPA. Because MPAG can favor the elimination of MPA, it can be concluded that gender differences and cotreatment with tacrolimus must be taken into consideration when MMF is being administered.

Is work a risk factor in the prescribed psychotropic drug consumption of female white-collar workers and professionals?

This article provides information on the prevalence and the characteristics of consumption of prescribed psychotropic drugs among unionized female white-collar workers and professionals in Montreal Canada. The objective of this paper is also to raise hypotheses on the contribution of certain professional factors to women's long-term use of psychotropic prescribed drugs. Data were collected through a questionnaire mailed to participants' homes. Results showed that prescribed psychotropic drugs are being used in the context of work. About 15% of the working women did use prescribed psychotropic drugs during the twelve months preceding the survey, and 5% of respondents reported a high level of consumption. Working women had a tendency to maintain consumption practices in line with their doctor prescription. Results also suggest that the work environment influenced prescribed drug consumption.

[Hypothesis on suicidal behavior as interpersonal communication.]. / Hypothèse sur le comportement suicidaire en tant que communication interpersonnelle.

Traditionnaly, suicidal behavior has been analysed through its individual and intrapsychic components and by its links with economic and social factors. To consider suicide as a message to the environment, then by highlighting its communicationnal aspect, is a new trend in the field. In fact, suicide often has a profound impact on the personal environment of the suicidal person. We therefore set forth the following hypothesis : suicide myths and tabous might be a social rationalization and defense mechanism against the violent impact of suicidal behavior. This paper explores the communication view point of suicidal behavior which interestingly open up new possibilities in the research and intervention on suicide.