Pharmacology is derived from the ancient Greek word for a drug, pharmakon, and is the study of how drugs and xenobiotics affect body function and also how the body will act on the drug. The use of chemicals to induce a response on the body is as old as time itself, whether through the use of herbal remedies as the earliest forms of medicine, or perhaps the dubious creation of poisons to rid individuals of enemies. Thus the (unintentional) practice of pharmacology might have been considered earlier in history as magic. The intentional formation of pharmacology as a scientific discipline has evolved from our need to apply scientific principles to create better medicines to improve clinical practice, emanating from an understanding of physiology and pathology, and the earlier exploits of apothecaries to the present creation of a pharmaceutical industry ( Fig. 2.1 ). Pharmacology requires an understanding of other disciplines such as pathology, physiology, biochemistry, synthetic chemistry and molecular biology, and it is underpinned by fundamental physical concepts of mass action and mathematics.
As with the emergence of any scientific discipline, there are a set of codifying rules and an identifiable taxonomy to allow drugs with similar clinical uses, or actions on classes of receptors, to be grouped and classified together via the use of a common naming system.
Drugs will have brand names that are identifiable to consumers and follow no consistent naming pattern. Furthermore, brand names for the same drug may vary from country to country and from manufacturer to manufacturer and therefore should generally not be used. On the other hand chemical names are exact and follow the strict criteria based on their molecular structure by the International Union of Pure and Applied Chemistry (IUPAC). Chemical names are necessary because they allow scientists to interpret the exact structure of a chemical, needed during their synthesis by chemists and by regulatory agencies. Drugs approved for marketing and pharmacological tools used in research will also often have another non-chemical generic name that identifies their pharmacological classification usually by one of the criteria set out below:
Pharmacological or molecular mechanism of action
Chemical nature or source
Of course, not all compounds have a therapeutic indication, as many are used as research tools, and some compounds might not have a known molecular mechanism of action. However, using the different classifications above, salmeterol would be classed as a bronchodilator/sympathomimetic, β 2 adrenoceptor agonist, or a phenylethanolamine. Most β 2 adrenoceptor agonist names end in rol. The registered brand commercial name for salmeterol is Serevent, a name that provides distinctiveness in the marketplace. Its IUPAC name on the other hand is 2-(hydroxymethyl)-4-[1-hydroxy-2-[6-(4-phenylbutoxy)hexylamino]ethyl]phenol. Perhaps the most useful classification of all these names is the use of β 2 adrenoceptor agonist: from this we understand the type of receptor salmeterol acts on, and therefore its primary pharmacological effect. The use of rol in salmeterol also informs us of this precise pharmacological action.
Some examples of pharmacological drug classifications are listed in Table 2.1 . The naming of antibodies is also codified, based on structure, and the taxonomy of ‘biologics’ is shown in Figure 8.5 ( Chapter 8 ).