Analgesics

Analgesics, Analgetica (from Greek a- negative particle, and algos-pain), substances that selectively depress the brain centers that perceive pain. Morphine acts most specifically in this regard, often used in combination with other opium alkaloids (in pantopone, proposed by Sahli), as well as in combination with atropine. In recent times, substitutes for morphine as an analgetic have been proposed, for example, eucodal. In addition to morphine and chemically related substances that are nervina in the proper sense of the word, there is a large number, mainly centrally acting substances, belonging to the large pharmacological group of antipyretics; the latter have an effect on both the thermoregulatory center and the pain centers. Analgetically acting substances are found in all chemical groups of antipyretics: 1) in the salicylic acid group (especially aspirin), 2) of antipyrine (especially pyramidon), 3) of quinine (the latter group, as a quinoline derivative, should also include the analgetically acting atophan) and 4) in derivatives of aniline and paraaminophenol (especially phenacetin). Substances of these groups are very often combined in practice, because when this is done, a potentiation (mutual enhancement) of the therapeutic effect is observed. The same potentiation is observed when they are combined with morphine, as well as with narcotic hypnotics (for example, veramon proposed by Starkenstein - a combination of pyramidon with veronal). Cannabis preparations are significantly less specific as analgesics. The group of morphine and the group of antipyretics exhaust the analgetics in the proper sense of the word. However, a whole range of pharmacologically different acting substances are used to reduce pain sensitivity, which in medical practice constitute the large general group Antineuralgica (from Greek anti-against, neuron-nerve and algos-pain). In addition to substances acting on pain centers, substances that reduce the sensitivity of the peripheral nervous system are used as Antineuralgica, among them the so-called local anesthetics. These include substances acting mainly due to the cooling they cause, low-boiling narcotics, such as chloroethyl, as well as substances of the cocaine group, used for injection into the nerve trunk affected by neuralgia (for example, Eucain /3). The ability to reduce pain sensitivity of nerve endings is also possessed by a number of other substances applied to the skin: menthol and, to a lesser extent, preparations of belladonna and henbane. In addition, Anaesthetica dolorosa are used: aconitine, veratrine, gelsemine, delphinine, coniine. In practice, only the first two alkaloids are used almost exclusively, with veratrine only locally and aconitine administered internally. When using substances of the latter group, an attempt is made to achieve a more or less long-term disruption of nerve function. This tendency is even more pronounced in the case of using alcohol (70-80°) for injection into the nerve trunk (containing exclusively sensory fibers, for example, n. trigeminus), which leads to its degeneration. Since the sensation of pain is often associated with impaired blood supply to the affected organ, substances that directly or indirectly affect this function are also included among Antineuralgica. Pain-relieving effect most often occurs when prescribing substances that dilate blood vessels. These include the aforementioned antipyretics, which are almost always administered in combination with caffeine (or with diuretin) as a substance that also dilates peripheral vessels. In addition to those mentioned, vasodilating substances of the amyl nitrite group are also prescribed (for angina pectoris, etc.). The analgesic effect of substances that eliminate spasm of the smooth muscles of internal organs should also be mentioned. These substances, often called Spasmolytica, include atropine, adrenaline (often used locally where possible - in the form of suppositories, sticks, etc.), as well as papaverine, emetine and some others. In addition to the above substances that directly dilate blood vessels, a large group of skin-irritating substances that cause reflex dilation of blood vessels of both the skin itself and the underlying deep tissues is often used as Antineuralgica. The analgesic effect can also occur frequently with vasoconstriction, but only in the latter case is achieved by the action of cold, because substances possessing the specific property of vasoconstrictors (adrenaline) do not give a pronounced effect in this regard. In addition to skin-applied agents (see above about chloroethyl), the action of cold is used partly when injecting a cooled physiological solution into the nerve trunk. The substances considered, with the exception of the caffeine and amyl nitrite groups, also have anti-inflammatory properties, which is why they are especially valuable in pains of inflammatory origin. But if, in the case of using skin-irritating agents, these properties are associated with causing hyperemia that acts favorably on inflammatory processes, then in the case of using proper analgetics and local anesthetics, they are reduced precisely to the suppression of pain, which can prevent or weaken the intensity of the inflammatory reaction. In addition to the above, a number of etiotropically acting agents belong to the group of analgesics. Here, first of all, the same antipyretics should be named: quinine for malaria; quinine, substances of the salicylic acid group and, partly, antipyrine for influenza and rheumatic infections, i.e., precisely in diseases most often accompanied by neuralgias. This also includes methylene blue, which acts etiotropically in malaria, but is also prescribed for neuralgias of other etiology (the mechanism of analgesic action in the latter case is little studied and with the expressed neurotropy of the dye, its action on both central and peripheral sensory elements can be assumed); further, preparations of mercury, arsenic, iodine - in luetic neuralgias, etc. In addition, among Antineuralgica there are substances specifically prescribed for neuralgias of gouty origin: atophan and colchicine (the mechanism of action of the latter is unknown). Special mention should be made of the treatment of neuralgias in anemia and malnutrition. Here, in addition to general strengthening agents (iron, arsenic, glycerophosphates), not analgesics but preparations of bromine and valerian are often prescribed. Finally, in inflammatory neuralgias, protein therapy is used, with vaccineurin often recommended, which is a mixture of autolysates of Bac. prodigiosus and Staphylococcus. Being one of the many preparations proposed for non-specific therapy, it cannot be considered specific for the treatment of neuralgia. Lit.: Starkenstein E., Der Einfluss experimentell pharmakologischer Forschung auf die Erken-nung und Verhutung pharmakotherapeutischer Irrtu-mer, Lpz., 1923; Spiess &., Die Bedeutung der Anasthesie in der Entzundungstherapie, Miinchener medizinische Wochenschrift, 1906, №8; Bruce A., tJber die Beziehung der sensibelen Nervenendigungen zum Entztindungsvorgang, Archiv I. experimentelle Pathologie u. experimentelle Pharmakologie, B. XCIII, 1910; Vogt H., Handbuch d. Therapie d. Nervenlcrankheiten, B. II, Jena, 1916.