Pharmacology

PHARMACOLOGY. In English-speaking countries, and by the majority of German writers, the term pharmacology is applied to the study of the action of chemical substances (as apart from foods) on all kinds of animals, from bacteria up to man; it is, in fact, a comparative study of the action of chemical bodies on in vertebrate and vertebrate animals.

Pharmacology is a branch of biology; it is also closely con nected with pathology and bacteriology, for certain drugs produce structural as well as functional changes in the tissues, and in germ diseases the peculiar symptoms are caused by foreign substances (toxins) formed by the infective organisms present in the body. The effects of many of these toxins bear a close resemblance to the action of certain well-known drugs, as in the case of tetanus toxin and strychnine, and are studied by the same methods.

The rapid growth of the science of pharmacology has been one of the most striking features of the development of the science of medicine during the twentieth century.

Organic Chemistry.

The only substances available for medi cal use a century ago were certain inorganic salts and crude vegetable extracts. The development of organic chemistry pro vided therapeutics with purified active principles of the crude vegetable extracts, and thus the use of crude preparations of unknown strength was replaced to a large extent by the use of chemical substances of known composition. Organic chemistry rendered a still more important service to pharmacology with the synthesis of organic compounds by which the number of sub stances available for use in therapeutics was increased indefinitely.

The anaesthetics, ether (1846) and chloroform (1847), were the first synthetic organic compounds to be used extensively in medicine. Twenty years later the first synthetic hypnotic, chloral hydrate, was introduced, and about 1885 the coal tar antipyretics, acetanilide and antipyrin, were discovered. Since then hundreds of new and valuable synthetic drugs have been discovered.

Salvarsan.

The discovery by Ehrlich in 1910 of salvarsan (q.v.), a potent remedy for syphilis, established a new method of research which has since yielded other results of great impor tance and promises to produce even greater successes.

In his search for a substance which would kill the infectious organism of syphilis (q.v.), the Treponema pallidum, without in juring the patient, Ehrlich started with the knowledge that allied organisms, the trypanosomes, were killed by certain dyes and organic arsenic compounds. Not content with a random examina

tion of the known compounds, he determined quantitatively which types of compounds were the most satisfactory for his purpose and then got new compounds prepared according to a definite plan. He made a systematic examination of a long series of organic arsenic compounds, determining in each case the minimal dose of the drug which would cure an animal infected with trypanosomes (minimal curative dose) and the maximal dose which the animal could tolerate (maximal tolerated dose). He termed the ratio:— (maximal tolerated dose) (minimal curative dose) the therapeutic index, and sought for a drug with the highest possible therapeutic index. The compound salvarsan or arseno benzole was the 606th arsenic preparation investigated, and in 1910 it was introduced as a remedy for syphilis. Two years later, Ehrlich introduced neosalvarsan or novarsenobenzole, which has to a large extent replaced salvarsan in the treatment of syphilis (see VENEREAL DISEASES). Ehrlich's brilliant success stimulated an intensive investigation of the action of organic metallic com pounds upon diseases due to infections by animal parasites.

New Methods.

A number of important new methods of treat ment have been discovered. Intramuscular injections of bismuth salts have been found to be of value in the treatment of cases of syphilis which are refractory to the organic arsenicals. Salts of antimony also have been found to have important new therapeutic actions. A century ago the production of subacute antimony poisoning by large doses of tartar emetic was a routine treatment for a very large number of diseases, but the revolt against the "heroic'' methods of treatment of disease, in the middle of last century led to tartar emetic being almost abandoned as a thera peutic agent. The drug was discovered to possess the new and important therapeutic action of acting like arsenic as a specific disinfectant for animal parasites (see HOOKWORM). Intravenous injections of antimony salts have been found of great value in treating various diseases due to trypanosomal infection, and also have been found to cure the disease bilharziasis (q.v.).