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 (meat of such animals is suitable for food, since the poison is poorly absorbed in the digestive tract). The most used are tubocurarine chloride, ditilin, diplacin and others, the drugs listed below. Curariform agents differ in the mechanism and duration of exposure.
History tour
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 this category of pharmacological drugs is considered to be skeletal muscle relaxation. For this reason, they are called muscle relaxants (from the Greek. Myos - muscle, and lat. Relaxatio - decrease) of the peripheral effect. It should be noted that numerous pharmaceutical substances that have a great effect on the central nervous system (central muscle relaxants), for example tranquilizers, have the property of reducing the activity of structural muscles.
Work mechanism
According to the mechanism of action, curariform agents should be divided into types:
- Antidepolarizing (competitive) type of exposure. Suppress the action of n-cholinergic receptors of skeletal muscles and prevent their excitation by acetylcholine, prevent the onset of muscle fiber depolarization. Tubocurarine, diplacin, meliktin, etc. immediately cause relaxation of muscle fibers.
- Depolarizing type of exposure that activates the depolarization of the cell membrane, the contraction of muscle fibers.
- A complex type of exposure, providing antidepolarizing and depolarizing results (dioxonium, etc.). Muscle relaxants activate muscle relaxation in a specific order: facial muscles of the face, limb muscles, vocal cords, body, diaphragm and intercostal.
Classification
According to the duration of exposure, muscle relaxants should be divided into 3 categories:
- short-term exposure (5-10 minutes) - ditilin;
- medium duration (20-40 minutes) - tubocurarine chloride, diplacin, etc .;
- prolonged exposure (60 minutes or more) - anatruxonium.
Curara-like remedies include drugs that are listed below.
Tubocurarine chloride
It is used in anesthesiology as a muscle relaxant (a muscle-calming substance), in traumatology during reposition (combining) of fragments and reposition 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 a substance forms 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, with relaxation lasting 20 minutes. Typically, for an operation lasting more than 2 hours, 45 mg of the substance is used.
Enter tubocurarine chloride only after the patient switches to artificial respiration. If necessary, interrupt the effect of the substance is administered 2.5 mg of proserin (an antagonist of curare-like drugs) after early intravenous administration of 1/2 mg of atropine. The introduction of the substance will require caution, as it can provoke respiratory arrest. If necessary, to reduce the effects of the drug put proserin.
Contraindications:
- myasthenia gravis (muscle impotence);
- a manifest disorder in the functioning of the urethra and gastrointestinal tract;
- old age.
Diplacin
Enter 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. With an action of two hours or more, 30 milliliters of a 2% solution.
If necessary, interrupt the effect of the substance is administered 2.5 mg of proserin (antidepolarizing curariform drug) 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), it does not activate muscle fasciculations. It does not show hormonal effects.
Even in doses several times higher than the effective dose required for a 90% reduction in muscle contractility, it does not show ganglion-blocking, 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 0.04 mg / kg guarantees 45 minute muscle relaxation during various procedures.
The maximum effect of pipecuronium bromide depends on the amount of drug administered and begins in a couple of minutes. The result is more rapid with portions of 0.7 mg / kg. A subsequent increase in dose will reduce the time required to obtain a result and significantly increase the effect of pipecuronium bromide.
Dithilin
Enter directly into a vein. During the intubation procedure (insertion of a tube into the trachea for the implementation of artificial respiration) and for absolute muscle fatigue, a medical preparation is administered at a dose of 2 mg / kg.
For long-term muscle relaxation throughout the entire procedure, it is possible to administer the medicine in small portions of 0.5-1.5 mg / kg. Secondary doses of dithilin function for a longer time.
Proserin and other anticholinesterase elements are by no means antagonists (elements with a reverse effect) in the relationship of the depolarizing effect of dithilin; on the contrary, suppressing the dynamics of cholinesterase, they lengthen and increase its effect.
In case of complications due to the use of dithilin (prolonged suppression of breathing), an apparatus is used to support, and if necessary, blood is transfused, introducing cholinesterase in a similar way. It should be borne in mind that in large portions, dithilin can provoke blocking if, after a depolarizing effect, an antidepolarizing result is formed.
For this reason, if after the final injection of dithilin muscle relaxation does not last long (for half an hour) and breathing does not completely resume, prozerin or galantamine is administered intravenously after the preliminary administration 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 truly qualified doctors, in prescribed doses and with the support of special equipment. Any deviation from the norm entails a grave consequence that can cost a human life.