Population pharmacodynamics of doxacurium

Assumption testing in population pharmacokinetic models: illustrated with an analysis of moxonidine data from congestive heart failure patients

Deriving a population pharmacokinetic model from real data is always associated with numerous assumptions. Violations of these assumptions, especially if undetected, may lead to inappropriate conclusions being made from the analysis. Routinely, only a few of the assumptions are explicitly stated and justified in the reporting of a population model. Here, we attempt to be exhaustive in the presentation of the assumptions made in the course of an analysis of moxonidine pharmacokinetics. The different ways that assumptions were justified, through experience, graphical examination, or additional modeling, are outlined. Models for relaxing assumptions regarding the covariate and statistical submodels, not previously reported in the area of population pharmacokinetic modeling, are also described.

Anaesthetic drugs in the elderly

The outcome of surgery in the elderly depends on the skill of the surgeon and the expertise of the anaesthetist caring for the patient. This anaesthetic proficiency depends initially on the application of the detailed knowledge of the drugs used during anaesthesia, and on the understanding of the way changes in the elderly patients' physiology with ageing affects both kinetic and dynamic facets of pharmacology. However, the very diversity of the elderly population makes their precise response to drugs unpredictable, and, therefore, clear, unequivocal guidance on practice is limited. The important changes in both physiology and pharmacokinetics with ageing are discussed before covering the specific drugs used in current anaesthetic practice in the United Kingdom. This review covers the drugs used primary for the induction and maintenance of anaesthesia, and only covers related fields where there are changes in recent practice that raise issues of importance during surgery. This review, therefore, deals mainly with the anaesthetic vapours and intravenous drugs, and with neuromuscular blocking agents. The restriction of space and the enormity of the subject demand that the areas covered in this review are solely limited to the major classes of drugs used routinely in general anaesthetic practice in the United Kingdom. The detailed pharmacokinetics and pharmacodynamics of drugs also used in the post-operative period, such as the wide variety of opiates, and of drugs mainly used in general medical practice, but occasionally used as premedicants or supplements during anaesthesia, have been monitored only in passing.

Pharmacokinetic and pharmacodynamic data and models in clinical trials

There is current emphasis for extended integration of pharmacokinetics (PK) and pharmacodynamics (PD) into all phases of new drug development, including large-scale clinical trials. In this paper, we focus on study design and data analysis issues for the investigation of pharmacokinetic/pharmacodynamic and blood level/effect relationships in patients. The application of descriptive and model-based regression statistical methodology for including sparse drug systemic concentration data in the analysis of efficacy and safety is illustrated by examples chosen from diverse therapeutic areas. The population approach, based on mixed-effects modelling, is one such methodology, which also provides new tools for analysis of response vs dose and response vs time data. The existence of a variety of statistical techniques for handling complex PK/PD time-varying data should increase the impact of such data analysis on future drug development.