Absorption kinetics of paracetamol are not influenced by high anxiety levels in preoperative patients

Prediction of dose-hepatotoxic response in humans based on toxicokinetic/toxicodynamic modeling with or without in vivo data: a case study with acetaminophen

In the present legislations, the use of methods alternative to animal testing is explicitly encouraged, to use animal testing only 'as a last resort' or to ban it. The use of alternative methods to replace kinetics or repeated dose in vivo tests is a challenging issue. We propose here a strategy based on in vitro tests and QSAR (Quantitative Structure Activity Relationship) models to calibrate a dose-response model predicting hepatotoxicity. The dose response consists in calibrating and coupling a PBPK (physiologically-based pharmacokinetic) model with a toxicodynamic model for cell viability. We applied our strategy to acetaminophen and compared three different ways to calibrate the PBPK model: only with in vitro and in silico methods, using rat data or using all available data including data on humans. Some estimates of kinetic parameters differed substantially among the three calibration processes, but, at the end, the three models were quite comparable in terms of liver toxicity predictions and close to the usual range of human overdose. For the model based on alternative methods, the good adequation with the two other models resulted from an overestimated renal elimination rate which compensated for the underestimation of the metabolism rate. Our study points out that toxicokinetics/toxicodynamics approaches, based on alternative methods and modelling only, can predict in vivo liver toxicity with accuracy comparable to in vivo methods.

The effect of stress on absorption of acetaminophen

RATIONALE

There is a large variability in the response to pharmacological treatment. Some studies have linked this variability to stress levels, i.e., stress may slow and/or reduce absorption of drugs.

OBJECTIVES

The present experiment investigated the hypothesis that stress slows absorption of drugs.

METHODS

Twenty-four volunteers participated in a within-subjects design with three conditions, each lasting 70 min. Subjects watched a movie hypothesized to induce stress, subjects listened to music hypothesized to reduce stress, and in a control condition no stimuli were presented. Each condition was spaced 2 days or more apart. In each condition, subjects received 500 mg oral acetaminophen. Measures of stress and acetaminophen levels were obtained every 10 min.

RESULTS

Indices of subjective stress and arousal and cortisol, were increased during the movie compared to control. Subjective arousal and cortisol were decreased during music compared to control. However, acetaminophen levels were the same across time in all three experimental conditions.

CONCLUSIONS

There was no effect of the experimental manipulations on acetaminophen absorption, indicating that stress was not related to drug absorption. However, stress could play a role in other processes related to drug pharmacokinetics.