Diaphoretics

DIAPHERETICS, agents used to induce increased sweating. They can be of a physical (heat, warmth) or chemical (medicinal substances) nature. For the first, see Sweating. Medicinal diaphoretics (diaphoretics, sudorifica, or eudorifera, hidrotica) have been used for a long time in folk and scientific medicine, usually in combination with physical agents that enhance sweating. According to the point of application of their action, these medicinal substances can be divided into the following groups: I. D. that exert an excitatory action on the secretion of sweat glands through the nervous system: 1) excitatory endings of secretory nerves in the glands after absorption into the blood (pilocarpine, to a lesser extent arecoline, eserine, etc.), 2) excitatory sweat centers (in the brain and spinal cord) either by direct resorptive action (pilocarpine, camphor, many convulsive poisons like strychnine, coramine, etc.) or reflexively due to irritation of sensitive nerve endings (Ammonium aceticum and others); medicinal substances that cause nausea and vomiting while at the same time increasing sweating stand close to this subgroup. II. D. that cause sweating due to direct resorptive action on the secretory cells of sweat glands (salicylic acid and its preparations, substances that irritate the skin, etc.). III. D. that increase sweating due to increased skin blood circulation: 1) dilating skin vessels due to direct local action on them (mustard, camphor alcohol and other skin-irritating agents), 2) inhibiting the vasomotor center due to direct resorptive action on it (alcohol, and according to some authors also salicylic acid and its derivatives, antipyrin, antifebrin and other antipyretic agents, etc.) or reflexively from the stomach (expectorants, emetics, etc.) and other organs. Such a classification, although it covers very many of the known D., nevertheless suffers from essential deficiencies, since it does not fully reflect the mechanism of the diaphoretic effect of these agents, does not reveal their therapeutic significance and creates groups of agents divided by only one sign and therefore often entering simultaneously into different classification groups. However, at present this classification, mainly proposed by Sollmann, is still apparently the best, since it contains an attempt to shed some light on the mechanism of action of D., the pharmacodynamics of which are very little developed in most cases. This especially applies to the action of numerous medicinal plants, infusions and decoctions of which are widely used to increase sweating. Among them the following can be named: linden blossom, flowers of black elderberry, flowers of common chamomile, leaves of melissa (Folia Melissae), raspberry berries, carnation flowers, bugloss, or borage (Flores Borraginis officinalis), dandelion leaves, flowers and stems of wild pansies, roots of salsify, or white scorzonera, burdock, or horsetail, sorrel, sarsaparilla, guaiac wood, sassafras and many others. The diaphoretic action of some of these agents was attempted to be explained by the presence of essential oils in them, however this is hardly correct, since in linden blossom essential oil is contained only about 0.04%, in elderberry flowers even less, and in the decoction of dried raspberry it is not possible to detect at all. Since decoctions and infusions from these plants (1-3 teaspoons of dried flowers in 0.5 liters of water) are taken hot, the diaphoretic action of them must certainly be partly attributed to the relatively increased amount of warm (hot) water introduced inside; however such an explanation is clearly insufficient for understanding the entire effect caused by them. Therefore some assume the possibility of direct resorptive action of still unknown active principles of these plants on gland cells, sweat or vasomotor centers and skin vessels. Regarding antipyretic agents of the salicylic acid group, alcohol and some other D., it is known that sweating is promoted by their inhibition of the thermoregulatory center*, and through it the vasomotor center. In this case the strength of action of this group of agents increases significantly in the case where the central nervous system is in an excited state (for example during fever). Smaller and more transient effects are given by agents acting reflexively on the vasomotor center or exerting a local action on skin vessels (directly or through axon reflexes); their application is therefore more limited. Increased skin blood circulation undoubtedly takes place in the first group of D., since general sweating usually goes parallel with the degree of skin blood filling, however here the change in circulation is only a subsidiary moment in the diaphoretic action, since the terminal apparatus of secretory nerves, as is known, always respond better to central or peripheral irritation with warm than with cold skin; at the same time increased circulation creates better conditions for nutrition, and consequently for the activity of sweat glands. Of agents of this group the strongest is pilocarpine (see). It is possible that at least some of the above-mentioned D. contribute to the giving off of water by tissues and blood, as a result of which water is more easily excreted by sweat glands. This especially applies to those D. which at the same time are also diuretics. Depending on the properties or state of water metabolism in a given organism, the diaphoretic effect can therefore be different. Apparently the fact that D. under equal conditions act more strongly on children and less on old people is in a certain dependence on this. Large amounts of sweat often excreted when applying D. have obvious therapeutic significance in appropriate pathological states, since thanks to this increased giving off of water, increased giving off of heat into the surrounding environment and increased excretion of salts, metabolic products, toxins and poisons takes place. As a result, D. are applied in the following pathological states: 1) In edemas and exudates in various cavities (pleuritis, pericarditis, etc.). 2) In signs of intoxication by endogenous (metabolic diseases) or exogenous (infectious diseases, poisoning) poisons, since iodine, bromine, boron, phenol, salicylic acid, salol, antipyrin, methylene blue, arsenic, antimony, some heavy metals (Pb, Hg, Bi, Ag), quinine, lactic acid, benzoic acid, succinic acid, ether, camphor, essential oils, musk, etc. are excreted with sweat. D. are especially often applied in chronic poisoning by heavy metals/, 3) In disturbances of skin, blood circulation (rheumatic diseases, pneumonia, pleurisy, etc., cooling of the skin for various reasons), in order to influence the circulation of internal organs by increasing skin blood circulation and lower the body temperature or restore the nutrition of the skin itself, if it was insufficient (for example in some skin diseases). In hyperemia and exudative lesions of the vascular coat of the eye, in retinal detachment, in toxic blindness, etc. 4) In metabolic diseases (obesity, gout, etc.) with the calculation to increase metabolism. 5) With the aim to cause skin hyperemia to accelerate the appearance of exanthems in some acute infectious diseases and thus establish the presence of a certain disease. 6) Sometimes D. are applied to obtain skin hyperemia in order to enhance the absorption of ointments, etc. The effectiveness of action of D. in the overwhelming majority (except pilocarpine) is not great compared to physical methods of increasing sweating; moreover the strength of action of physical agents can be more easily regulated than chemical ones. Large doses of pilocarpine are dangerous due to the possibility of its side effect (see Pilocarpine); the same applies to salicylic preparations and especially to convulsive poisons (strychnine, etc.), the application of which as D. is now abandoned. Contraindications to the application of D. are far-advanced phenomena of degeneration of the heart muscle and vessels, general weakness, and for pilocarpine in addition pregnancy. Of the D. listed above, at present the most commonly used are hot infusions and decoctions from medicinal plants (linden blossom, elderberry blossom, chamomile, melissa, raspberry), salicylic acid preparations (aspirin, sodium salicylate, etc.), antipyrin, camphor.