Curare is the only type of arrow poison. Penetrating into the body of an animal, the poison causes stagnation of skeletal muscles, and the creature loses the ability to move (the meat of such animals is suitable for food, since the poison is poorly absorbed in the gastrointestinal tract). The most used are tubocurarine chloride, ditilin, diplacin and other drugs listed below. Curare-like drugs differ in mechanism and duration of action.
A trip to history
In 1856, the famous French physiologist Claude Bernard determined that the poison blocks the transmission of excitation from the motor nerves to the skeletal muscles. In Russia, regardless of Claude Bernard, the same results were obtained by the popular forensic chemist and pharmacologist E. V. Pelikan. The main result of the action of this category of pharmacological drugs is the relaxation of skeletal muscles. For this reason, they are called muscle relaxants (from the Greek myos - relax, and lat.atio - decrease) of the peripheral type of exposure. It should be noted that numerous pharmaceutical substances have the property to reduce the activity of structural muscles, which have a great influence oncentral nervous system (central muscle relaxants), such as tranquilizers.
Working mechanism
According to the mechanism of action, curare-like drugs should be divided into types:
- Antidepolarizing (competitive) type of influence. They suppress the action of n-cholinergic receptors of skeletal muscles and prevent their excitation by acetylcholine, prevent the onset of depolarization of the muscle fiber. Tubocurarine, diplacin, meliktin, etc. immediately cause relaxation of muscle fibers.
- Depolarizing type of effect that activates the depolarization of the cell membrane, the contraction of muscle fibers.
- Complex type of action, providing anti-depolarizing and depolarizing results (dioxonium, etc.). Muscle relaxants activate muscle relaxation in a specific order: facial muscles, limb muscles, vocal cords, body, diaphragm and intercostal.
Classification
By duration of exposure, muscle relaxants should be divided into 3 categories:
- short-term exposure (5-10 min.) - dithylin;
- medium duration (20-40 min.) - tubocurarine chloride, diplacin, etc.;
- prolonged exposure (60 min. and more) - anatruxonium.
Cure-like drugs include the drugs listed below.
Tubocurarine chloride
Used in anesthesiology as a muscle relaxant (a substance that calmsmuscles), in traumatology during reposition (combination) of fragments and reduction of difficult dislocations, in psychiatry to prevent injuries during convulsive therapy in patients with schizophrenia, etc. An injection is made into a vein.
The effect of the substance is formed over time, as a rule, muscle relaxation occurs after 60-120 seconds, and the maximum effect begins after 4 minutes. The average serving for an adult is 20 mg, while relaxation lasts 20 minutes. As a rule, for an operation lasting more than 2 hours, 45 mg of the substance is used.
Introduce tubocurarine chloride only after the patient switches to artificial respiration. If necessary, interrupt the effect of the substance, 2.5 mg of prozerin (an antagonist of curare-like drugs) is administered after advance intravenous administration of 1/2 mg of atropine. The introduction of the substance will require precautions, as it can provoke respiratory arrest. If necessary, to reduce the effects of the drug, put prozerin.
Contraindications:
- myasthenia gravis (muscular impotence);
- manifest disorder of the functioning of the urinary system and gastrointestinal tract;
- old age.
Diplacin
Inject intravenously (slowly - over 3 minutes) 150 mg of diplacin (7 milliliters of a 2% solution), an average of 2 mg per kilogram of body weight. For an action lasting two hours or more - 30 milliliters of a 2% solution.
If necessary, interrupt the effect of the substance, 2.5 mg of prozerin (antidepolarizingcurare-like agent) after preliminary parenteral administration of 1/2 mg of atropine. With the introduction of large doses, there is a slight increase in blood pressure.
Pipecuronium bromide
Due to the competitive relationship with n-cholinergic receptors, it blocks signal transmission to the muscles. Acetylcholinesterase inhibitors are considered antidotes.
Unlike depolarizing muscle relaxants (for example, succinylcholine), does not activate muscle fasciculations. Shows no hormonal influence.
Even at doses several times higher than the effective dose required for a 90% decrease in muscle contractility, it does not show ganglioblocking, m-anticholinergic and sympathomimetic effects.
According to studies, with balanced anesthesia, the effective doses of pipecuronium bromide required for a 50% and 90% reduction in muscle contractility are 0.04 mg/kg, respectively.
A dose of 0.04mg/kg guarantees 45 minutes of muscle relaxation during different treatments.
The maximum effect of pipecuronium bromide depends on the amount of the drug administered and begins after a couple of minutes. The result develops more rapidly with portions equal to 0.7 mg / kg. Subsequent dose increases will shorten the time needed to get results and greatly increase the effect of pipecuronium bromide.
Ditilin
Injected directly into a vein. During the procedure of intubation (insertion of the tube into the tracheafor the implementation of artificial respiration) and for absolute muscle asthenia, a medical preparation is administered at a dose of 2 mg / kg.
For prolonged relaxation of the muscles throughout the entire procedure, it is possible to administer a medical agent in small portions of 0.5-1.5 mg / kg. Secondary doses of dithylin function for a longer time.
Prozerin and other anticholinesterase elements are in no way antagonists (elements with the opposite effect) in relation to the depolarizing effect of dithylin; on the contrary, by suppressing the dynamism of cholinesterase, they lengthen and increase its influence.
In case of complications due to the use of dithylin (prolonged suppression of breathing), a device is used for support, and if necessary, blood is transfused, introducing cholinesterase in a similar way. It must be taken into account that in large portions, dithylin can provoke a blockage if, after a depolarizing effect, an anti-depolarizing result is formed.
For this reason, if after the final injection of dithylin, muscle relaxation does not go away for a long time (for half an hour) and breathing is not fully resumed, intravenous prozerin or galantamine is administered after the preliminary introduction of atropine 0.6 milliliters of a 0.1% solution.
The list of substances can be continued for a long time. They are used only in a special institution, under the strict supervision of really qualified doctors, in prescribed doses and with the support of special equipment. Any deviation from the norma serious consequence that could cost a human life.
