FARMACOLOGIA. — The word, introduced into the medical vocabulary in 1600, in its etymology means the study of drugs (medicaments and poisons), and at first was confused with medicinal therapy. With the progress of knowledge, especially with the emergence of physiology, chemistry, and finally physical chemistry, the task of f. was in turn progressively defined, and today f. is understood as the biological science that studies drugs, understood as chemically defined substances capable of determining a functional variation through a chemical or physicochemical modification of the cellular protoplasm (not, therefore, through a physical modification). The purpose and task of f. are better appreciated by comparing them with those of physiology. Chemically defined substances are used in physiology for the purpose of studying functional modifications, and in this sense Cl. Bernard coined (1856) the significant expression that medicaments and poisons are, in the hands of the experimental physiologist, « true reagents of life ». For f., however, functional modifications are not the object of the investigation but its means: functional variations are studied as a means of assessing the chemical and physicochemical variations that have produced those functional variations. In this sense, functional variations have aptly been compared by Sabbatani to the changing of the colour of indicators in chemistry.
It is true that the drug as it is known, in its chemical and physicochemical characteristics, does not always remain unmodified when it comes into contact with the blood and tissue; hence it is also the task of f. to study how the drug is modified in the organism. The purpose of f. as a biological science would be to arrive, through the study of the activity of substances of known chemical constitution, at knowledge of the structure and dynamism of the protoplasm, that is, at penetrating the mechanism of life. In the meantime, more modestly, f. serves to provide a scientific basis (removing it from empiricism) for therapy by chemical means (as distinct from physical therapy and other forms of therapy).
From a conceptual point of view, it may be observed that the definition given of f. has value only if the independence of chemistry vis-à-vis physics is admitted. If chemistry were reduced to physics, the definition would have to be modified. But remembering that it is the scale of observation that creates (or delimits?) the phenomenon, and that f., like chemistry, is a science of the macroscopic, the reason for the existence of f. is the same as that of chemistry.
It is clear that f. makes use of experimentation on living beings or on surviving parts. Pharmacological experiments are therefore carried out on plants (microorganisms on which disinfectants and certain chemotherapeutic agents are tested are plants), on protozoa, and on animals of every type, class, and species. Each species serves to bring the drug into contact with the living cell; but whereas the unicellular organism comes into contact with the drug through all the surfaces of its body, in the metazoan, to confine ourselves to animals, there are natural or artificial routes for introducing drugs.
Isolated cells of metazoans, such as red blood cells, and surviving organs (heart, frog’s eye) are in turn excellent reagents for the biological investigation of drugs, which can act on relatively small substrates in proportionally minute doses, thus serving to establish the nature and dose of the drug used (biological investigation and dosage of drugs). A fundamental concept in f. is that of dose: « it is the dose that makes the poison »; for any substance may, depending on the quantity, be food, a drug, or a poison. Sodium chloride may serve as an example: it normally takes part in metabolism, its absence from food is felt through the need to introduce it, and a quantity of it is nevertheless known to be lethal. But since the concept of dose ultimately concerns a relationship between the live weight on which the drug acts and the weight of the drug, the fact that extremely small weights of a drug act on proportionally small living weights must not be misleading. It is then easy to speak of minimum doses, and it is possible that homoeopathic medicine may seek in these experimental results some support and pretext. But if one keeps in mind the relationship between the ponderal quantity of active drug and the weight of the living matter on which it has acted, the so-called minimum doses prove to be such only in relation to the small quantity of living matter (e.g., the mass of a red blood cell), and have nothing in common with the doses (concentrations) of homoeopathy.
A distinction is made between general f., special f., and therapeutic f. General f. deals with what is common to drugs, independently of their elective and specific action: absorption, the modifications they undergo in the organism, distribution, elimination, and the conditions and factors that modify their action. Special f. deals with the action of drugs according to their chemical classification. Therapeutic f. « has a preparatory, critical, and interpretive task with regard to the therapeutic applications of drugs » (Meneghetti).
Among the recent advances in f., those achieved by chemotherapy from Ehrlich onward should be mentioned, culminating in the discovery and application of « antibiotic » substances such as penicillin and streptomycin.