Magnesium

Magnesium, Magnesium, chemical element, symbol Mg, a silver-white metal belonging to the group of alkaline earth metals; atomic number 12. Atomic weight 24.32; specific gravity 1.75. When burned in air, it forms a white powder of magnesium oxide or magnesia. M. is widely distributed in nature, being a component of minerals: magnesite, dolomite, kieserite, asbestos, talc, and others. The chloride and sulfate salts of magnesium are present in seawater. Being widely distributed in the environment in which organisms live, M. is also constantly present in their blood and tissues. However, while the ratio of sodium, potassium, and calcium in blood serum is approximately the same as in seawater (for 100 atoms of Na, about 2 atoms of K and 2 atoms of Ca), the relative content of M. is significantly lower: for 100 atoms of Na in the blood serum of various mammals, there are only about 0.8 atoms of Mg. M. is widely distributed in the plant kingdom, being a component of chlorophyll. When entering the body with food, M. is excreted by the kidneys in the form of primary and secondary phosphates. The Mg ion has significance in the ionic equilibrium of the environment surrounding the cell, affecting various cell functions and reducing the toxic effect of other ions, and is a component of the nutrient salt solution proposed by Tyrode for the isolated intestine. Artificial increase in the magnesium ion content in the blood, created by parenteral administration of its salts (when administered per os, salts of M. are absorbed very slowly and excreted relatively quickly), causes a state characterized by complete immobilization of the animal and called "magnesium narcosis" (Meltzer, Auer). This state is instantly destroyed by intravenous administration of salts of Ca, so that even an animal close to death immediately begins to move vigorously. The antagonism of Ca with respect to the paralyzing action of M. is also manifested in the fact that an animal previously fed food rich in Ca and poor in M. is narcotized only by large doses of the latter; on the other hand, with simultaneous parenteral administration of oxalic salts^-, which precipitate Ca, narcosis is obtained from smaller doses compared to usual doses of magnesium. A more detailed study of "magnesium narcosis" showed that in its origin, paralysis of not only the central but also the peripheral nervous system plays a role. The participation of the latter is revealed by the curare-like action of salts of M. on the motor nerve endings in skeletal muscle, and physostigmine here is as much an antagonist of M. as with respect to curare. The action of salts of M. on the central nervous system is manifested by drowsiness, and then loss of consciousness. Probably the action of M. on the central nervous system should explain the decrease in temperature, as it occurs before the onset of narcosis and continues after awakening: An increase in temperature caused by centrally acting tetrahydronaphthalenes is eliminated by M. (interestingly, salts of Ca do not eliminate this action of M., but even aggravate it). It is believed that the antagonism of Ca and Mg is direct, i.e., both ions act on the same anatomical-physiological substrate (Straub even compares the speed of elimination of magnesium narcosis by calcium with the speed of "ionic reaction"). However, this opinion is not in agreement with the research of Yamawaki (Shoji Yamawaki), who showed that animals from which the large brain has been removed up to the thalamus (Thalamustier) not only do not awaken from magnesium sleep with salts of Ca, but give a picture of even deeper depression when they are administered; thus for such animals Mg and Ca are synergists. From these experiments it follows that the antagonistic action of Ca is localized in the higher parts of the brain (the Japanese author admits the exciting action of Ca on the striatum). It should be noted that the depressing action of both ions on body temperature, since the heat centers are localized in the intermediate and midbrain, is quite consistent with these experiments. However, an increased content of M. in brain tissue during magnesium narcosis could not be detected. In the blood, the magnesium content during it increases to 0.1-0.12%, i.e., 25-30 times higher than normal (0.0023-0.0040%). Deep magnesium narcosis is dangerous to life due to the proximity of narcotic and lethal concentrations of magnesium, and therefore Meltzer proposed a combined magnesium-ether narcosis, in which after the administration of salts of M., sufficient depth of narcosis for the operation is achieved only by a small amount of ether administered by inhalation. Synergists of M., also used for combined narcosis (or generally for calming the central nervous system), are morphine, scopolamine, fatty series hypnotics and other substances depressing the central nervous system. Salts of M. have been widely used in the treatment of convulsive states, mainly in traumatic tetanus. When using magnesium, careful observation of the patient is required (to monitor breathing, which during deep sleep becomes very shallow, and the heart, the rhythm of which can slow down very much, and blood pressure can decrease sharply), very precise individualized dosing and the availability of a calcium chloride solution for intravenous administration in life-threatening symptoms (5 cm³ of 20% solution). The sulfate and chloride salts of M. are used (the proposed magnesium glycerophosphate turned out to be a drug with side effects), and the methods of administration, dosage and strength of solutions recommended by various authors are very different (see below). Cumulation even with multi-day treatment with M. has not been noticed, since (due to their ability, like other salts, to increase diuresis, they are excreted relatively quickly by the kidneys. Less commonly, salts of M. are used in the treatment of eclampsia, spasmophilia, chorea, parkinsonism, etc. In veterinary practice, salts of M. are used to induce sleep (0.75 g per 1 kg), narcosis (1.5-1.75 g per 1 kg) and for painless killing of animals (1.75-2.0 g per 1 kg of weight). All doses refer to the subcutaneous method of administration. A much wider application of M. compared to the one just described has the local action of preparations of M., especially its action on the digestive tract. Many salts of M. are used as laxatives. Especially commonly used are the sulfate salt, chloride, citrate, carbonate, lactate, tartrate, phosphate salt, as well as calcined magnesia; these salts are converted in the intestine into bicarbonate of M., which is excreted with feces. The laxative action is associated with the fact that poorly diffusible salts of M. delay the absorption of water from the intestine and, greatly increasing the intestinal contents, stretch the intestines, which causes enhanced peristalsis. Some authors observed a laxative effect with subcutaneous administration of salts of M., probably partly due to reflex enhancement of peristalsis, partly due to the excretion of salts (especially sulfates) in the intestine. In the treatment of chronic constipation, obesity, etc., bitter waters containing salts of M. are prescribed (Batalinsky spring and others). Of particular importance is the content of M., mainly its sulfate salt, in a number of so-called bitter springs, used for therapeutic purposes. Especially rich in this salt are the Seidlitz and Püllna springs (Bohemia), containing it in the amount of 1-3%; less rich are Epsom (England), Montmirail (France) and Batalinsky spring (USSR-Pyatigorsk); the latter contains 0.84% of this salt. In addition, sulfate of M. is used in acute poisoning with barium and lead, with the expectation of forming insoluble salts of these metals in the intestine and removing them with feces. Calcined magnesia (and some other preparations of M.¹, see below) is prescribed to neutralize gastric contents (with increased acidity, fermentation, poisoning with acids); The advantage of the latter over sodium bicarbonate¹ is that it, while neutralizing acids, does not form carbon dioxide, which could cause undesirable and even dangerous (in acid poisoning) distension of the stomach. Calcined magnesia is also prescribed in acute arsenic poisoning and is included in the official Antidotum Arsenici. For the formation of poorly soluble compounds, it is sometimes prescribed in poisoning with alkaloids. In surgery, hypertonic solutions of sulfate and chloride salts (5-10%) are sometimes used in the treatment of purulent wounds (washing, wet dressings), with the aim of cleaning the wounds, increasing phagocytosis and reviving granulations. Hypochlorite of M.

(Magnocid), which releases active chlorine, is used similarly to Dakin's solution. Preparations. Magnesium sulfate, MgSO₄·7H₂O, magnesium sulfate salt, bitter salt, Epsom salt (GPh), formerly also called Zedlitz or Epsom salt—hygroscopic crystals soluble in 1 part cold water and 0.3 parts boiling water with a neutral reaction; used 1) as a laxative from 10.0 to 30.0 in ¹/₂-1 glass of water (to be followed by an equal amount of water); effect occurs in 3-4 hours; 2) for general effect to depress the central nervous system or to achieve combined anesthesia: a) subcutaneously 2-4 cm³ of 4-15% and up to 50% solution; b) intramuscularly 2-4 cm³ of 10-20% solution (0.04-0.06 g per 1 kg weight); c) intravenously 0.75-1.5 cm³ of 3% solution; d) subdurally (lumbar puncture) 0.25-2.5 cm³ of 10-25% solution (up to 1 cm³ of 25% solution per every 10 kg weight); with all these routes of administration, solutions must be sterile; e) in enema 4-6 cm³ of 3-20% solution (effect unreliable). - Magnesium sulfatum siccum, s. Magnesium sulf. siccum, magnesium sulfate dried (GPh), hygroscopic white powder, prescribed as a laxative in doses 2-3 times smaller than the previous preparation; unsuitable for parenteral administration. - Magnesium chloratum (crystallisatum), magnesium chloride (MgCl₂), colorless hygroscopic crystals, soluble in 0.6 parts cold water and 0.3 parts boiling water with neutral or slightly alkaline reaction, used like the first preparation to induce sleep. - Magnesium carb. basicum, s. Magnesium carbonicum basicum, s. Magnesia alba, basic magnesium carbonate, is a complex salt of MgCO₃ and Mg(OH)₂ combined with water; light white, easily triturable pieces or loose powder; very slightly soluble in water, giving it a slightly alkaline reaction; dissolves in acids with release of carbon dioxide. Used as an acid-neutralizing agent in doses of 0.3-1.0 and as a mild laxative in doses up to 2.0. Included in Pulv. Magnesiae cum Rheo. - Magnesium oxydatum, Magnesium oxydatum, s. Magnesia usta, calcined magnesium MgO (GPh), white loose powder, sparingly soluble in water (1:55,000); when dissolved in water gives a slightly alkaline reaction and forms a pasty mass of magnesium hydroxide-Mg(OH)₂; easily dissolves in diluted acids. As an acid-neutralizing agent—0.1-0.3 per dose; in acid poisoning—as a suspension (e.g., 100 g in 250 cm³ water; shake). Mild laxative for children in dose 1.0-1.5. - Magnesium citricum effervescens, effervescent magnesium citrate (GPh), white granules slowly soluble in water with release of carbon dioxide, forming colorless transparent solutions of pleasant sour taste; contains magnesium carbonate (5 parts), citric acid (23 parts), sodium bicarbonate (17 parts), sugar (4 parts); prescribed as a laxative in doses of 15.0-20.0! - Magnesium peroxydatum (Magnesium perhydrol), a mixture of magnesium peroxide hydrate, MgO(OH)₂, with magnesium hydroxide hydrate, Mg(OH)₂; white water-insoluble powder, dissolving in diluted acids with formation of H₂O₂. Used as a tooth powder, as an antiseptic and anti-acid in gastrointestinal diseases. - Talc, a mineral which is a polysilicate of Mg, Mg₃H₂Si₄O₁₃, the pharmaceutical preparation is a very fine white powder, odorless and tasteless, insoluble in water and most other solvents. Used per se for dusting, included in powders, etc. Magnesium is part of magnesium mixture (magnesium chloride, ammonium chloride and ammonia solution)—a reagent for phosphoric acid. In the form of powder and metal ribbon, it is used for flash in photography.