Pharmacokinetics and Pharmacodynamics of Abused Drugs PDF

Preface

This volume discusses pharmacokinetics and pharmacodynamics. Chapters 1 through 4 discuss aspects of pharmacokinetics. Chapters 5 through 8 discuss aspects of pharmacodynamics.

Pharmacokinetics is defined as the study of the quantitative relationship between administered doses of a drug and the observed plasma/blood or tissue concentrations. The field of pharmacokinetics is concerned with drug absorption, distribution, biotransformation, and excretion or elimination. These processes, in addition to the dose, determine the concentration of drug at the effector or active site and, therefore, the intensity and duration of drug effect.

The practice of pharmacokinetics has been used in clinical medicine for many years in order to optimize the efficacy of medications administered to treat disease. Through a consideration of pharmacokinetics, physicians are able to determine the drug of choice, dose, route, frequency of administration, and duration of therapy in order to achieve a specific therapeutic objective. In the same manner, study of the pharmacokinetics of abused drugs aids investigators in addiction medicine, forensic toxicology, and clinical pharmacology in understanding why particular drugs are abused, factors that affect their potential for abuse, how their use can be detected and monitored over time, and also provides a rational, scientific basis for treatment therapies.

Pharmacodynamics is the study of the physiological and behavioral mechanisms by which a drug exerts its effects in living organisms. An effect is initiated by the drug binding to receptor sites in a cell's membrane, setting in motion a series of molecular and cellular reactions culminating in some physiological (e.g., opioid-induced analgesia) or behavioral (e.g., alcohol-induced impairment) effect. Drugs typically have multiple effects. For example, a benzodiazepine will produce its primary anxiolytic effect, but may also cause side effects of sedation and impaired performance.

The question of the behavioral effects of abused drugs has been the focus of research by behavioral pharmacologists for many decades. Because of the widespread use of psychoactive drugs throughout society, employers have become increasingly concerned about drugs in the workplace and the potential for impaired job performance and onsite drug-related accidents. There are now computerized tests that employers can use to aid in the detection of impaired employees. Some drugs of abuse also produce characteristic effects on the visual system, and for this reason, devices that detect eye movement and function are also being tested for their ability to predict drug ingestion and potential impairment in the workplace.

Knowledge of both pharmacokinetics and pharmacodynamics is central to an understanding of drug abuse and its treatment.