ABSTRACT
Most primary-care physicians understand the use of medicinal drugs from both their training and daily care of patients. In this chapter we review absorption, metabolism, some factors influencing entry into the central nervous system (CNS), and tolerance of addicting drugs. Details about each drug are provided in later chapters describing each class of agents. For most classes of abused drugs there are several similar chemical forms that may be abused. Opiates, amphetamines, barbiturates, and benzodiazepine drugs are families with many representatives. Within each family there is a similarity of mode of principal action, cross tolerance is exhibited, but the methods of removal and the side effects are often quite different. New substances in each class are discovered each year, both by the legitimate pharmaceutical industry and by hidden chemists making “designer drugs” with potential for illicit use and profits.
