ABSTRACT
The study of drugs for the treatment of a disease, that are commonly chemical-based identities, ranging from a simple element (e.g. lithium) or to more complex organic molecules such as a benzodiazepine (e.g. diazepam), is known as pharmacology. In this regard, it is generally accepted that once efficacy and toxicological profiles of a drug have been established, based on animal and/or human studies, interest shifts to establishing dosage regimen and product development. In this regard, the objective is to achieve and maintain optimum therapeutic response by delivering appropriate drug amounts. The therapeutic response is generally dependent upon the drug concentration at the site of action in the body. The study of effect or response in relation to drug amounts, more specifically drug concentrations in different tissues of the body such as blood or brain, may be described as the pharmacodynamics. Generally speaking, if one draws a graph of responses (e.g. blood pressure readings) on a y-scale (linear scale) with dose on an x-scale (log scale), the graph will resemble the profile shown in Figure 15.1. The S-shape of the curve is generally known as a sigmoid curve or plot and forms the fundamental basis of pharmacodynamics.
