PHARMACOLOGY. - The word, introduced into the medical vocabulary in the 1600s, in its etymology means the study of drugs (medicaments and poisons) and at first was confused with drug therapy. With the progress of knowledge, especially with the emergence of physiology, chemistry, and ultimately physical chemistry, the task of pharmacology has in turn become defined, and today by pharmacology is meant 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 (and therefore not through a physical modification). The purpose and the task of pharmacology 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." But for pharmacology the functional modifications are not the purpose of the investigation, but the means: functional variations are studied as a means of judging the chemical and physicochemical variations that produced those functional variations. In this sense functional variations have been happily compared by Sabbatani to the changing color of indicators in chemistry.
It is true that the drug as it is known, in its chemical and physicochemical characters, does not always remain unmodified when it comes into contact with the blood and the tissue; therefore the task of pharmacology is also to study how the drug is modified in the organism. The purpose of pharmacology as a biological science would be to arrive, through the study of the activity of substances of known chemical constitution, at knowing the structure and dynamism of the protoplasm, that is, at penetrating the mechanism of life. Meanwhile, more modestly, pharmacology serves to give a scientific basis (drawing it away from empiricism) to therapy with chemical means (distinct from physical therapy and from other forms of therapy).
From a conceptual point of view it may be observed that the definition that has been given of pharmacology has value only if one admits the independence of chemistry with respect to physics. 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 pharmacology, like chemistry, is a science of the macroscopic, the reason for the existence of pharmacology is the same as that of chemistry.
It is clear that pharmacology makes use of experimentation on living beings or on surviving parts. Pharmacological experiments are therefore performed on plants (the microorganisms on which disinfectants and certain chemotherapeutic agents are tested are plants), on protozoa and on animals of every type, class and species. Every species serves to bring the drug into contact with the living cell; but while the unicellular living being comes into contact with the drug through all the surfaces of the body, in the metazoan, to confine ourselves to animals, there are routes of introduction of drugs, natural or artificial.
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 on relatively small substrates can act at proportionally very small doses, thus serving to establish the nature and the dose of the drug used (biological investigation and assay of drugs). A fundamental concept in pharmacology is that of dose: "it is the dose that makes the poison"; because any substance whatsoever can, depending on the quantity, be food, drug, or poison. As an example, sodium chloride may serve, which normally takes part in metabolism, whose absence in foods is felt, with the need to introduce it, and of which a lethal quantity is also known. But since the concept of dose is ultimately that of a ratio between the living weight on which the drug acts and the weight of the drug, one must not be misled by the fact that extremely small weights of a drug act on proportionally small living weights. It is easy then to speak of minimal doses, and it is possible that homeopathic medicine seeks in these experimental results some support and pretext. But if one keeps in mind the ratio between the ponderable quantity of the active drug and the weight of the living matter on which it has acted, the so-called minimal doses prove to be such only in relation to the small quantity of living matter (for example, the mass of a red blood cell), and have nothing in common with the doses (concentration) of homeopathy.
One distinguishes general pharmacology, special pharmacology, and therapeutic pharmacology. The general treats of what is common to drugs, independently of their elective and specific action: absorption, modifications they undergo in the organism, distribution, elimination, conditions and factors that modify their action. The special treats of the action of drugs according to their chemical classification. The therapeutic "has a preparatory, critical, interpretive task with respect to the therapeutic applications of drugs" (Meneghetti).
Among the recent advances of pharmacology, those achieved by chemotherapy from Ehrlich onward to the discovery and application of "antibiotic" substances, such as penicillin and streptomycin, must be mentioned.
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Luigi Seremin