TUBOKURARYN (Tubocurarinum; synonym: d-tubocurarine, Myostatine,
Tubadil, Tubarine, Tubocuran, d-Tubocurarini chloridum, etc.; SI. A) — kurarepodobny means; alkaloid of a curare; C38H4106N2C12 «5H20:
White crystal powder, easily water soluble.
T. is not depolarizing kurarepodobny means. Causes a relaxation of skeletal muscles. Mechanism of action of T. it is connected with the fact that it, interacting preferential with postsynaptic N-ho-linoretseptorami of skeletal muscles, interferes with exciting influence of acetylcholine on these receptors and, thus, causes neuromuscular block. A relaxation of skeletal muscles under the influence of T. occurs in a certain sequence. First of all the relaxation of chewing, mimic and cervical muscles is noted, then — muscles of extremities and a trunk. N-holinoretseptory of respiratory muscles have the greatest resistance to effect of drug (intercostal and diaphragms). Their relaxation is followed by an apnoea in this connection at use of T. artificial ventilation of the lungs is necessary (see. Artificial respiration). T. is a muscle relaxant of average duration of action. Duration of its effect makes from 20 to 40 min.
T. practically it is not soaked up from went. - kish. path. The Mioparalitiche-sky effect arises only at parenteral administration of drug. Apprx. 30% of once entered dose
of T. it is removed with urine within several hours. The insignificant amount of drug is distinguished with bile. At patients with an impaired renal function of T. can kumulirovat. Drug does not get through a placenta and a blood-brain barrier.
T. apply to a relaxation skeletal hmyshts hl. obr. during surgeries. For this purpose it is entered intravenously. Action of T. after intravenous administration develops gradually, the maximum effect occurs in 3 — 4 min. Extent of the muscle relaxation arising after introduction of T., estimate on a wedge, to signs and by means of an electromyography (see) in size of action potentials of muscles of a thumb of a palm at single and rhythmic electric stimulation of an elbow nerve. T. reduces amplitude of single answers, causes a so-called blanching test of evoked potentials at rhythmic irritation, and also post-theta-nichesky simplification of neuromuscular transmission.
Average mioparalitichesky dose of T. for adults makes 0,4 — 0,5 mg/kg.
At use of T. decrease in the ABP, a bronchospasm, strengthening of secretion bronchial and sialadens can be observed that is connected about Ganges-lioblokiruyushchim and gistaminogenny effect of drug. Decrease in coagulability of blood owing to the increased release of heparin from mast cells under the influence of tubocurarine is possible.
Means for an inhalation anesthesia (Ftorotanum, metoksifluran, an Aether anaesthesicus), and also strengthen tranquilizers from group of derivatives of benzodiazepine and prolong influence of T. on neuromuscular transmission. The neuromuscular block called by T., amplifies at acidosis and it is weakened at an alkalosis. Against the background of a hypopotassemia activity of T. increases. Antibiotics from group of aminoglycosides and ions of magnesium exponentiate action of T. due to reduction of secretion of acetylcholine presynaptic nerves of motor nerves. Tetracyclines and antagonists of calcium, napr, verapamil, also strengthen influence of T. on neuromuscular transmission. Besides, action of T. amplifies against the background of use of polymyxins A and B, colistin, clindamycin and lincomycin. Adrenaline and noradrenaline weaken influence of T. on neuromuscular transmission. Antagonists of T. aitikholinesterazny means (see), napr, prozerin are (see), to-ry usually apply together with atropine, and also 4 aminopyridines the hydrochloride (pimadin) strengthening allocation of acetylcholine from presynaptic nerves of motor nerves.
T. it is contraindicated at a myasthenia. The patient of advanced age, and also the patient with the expressed renal failures and a liver drug is appointed with care. Hypersensitivity to mio-laralitichesky action of T. it is noted at newborns.
Form of release: ampoules on 2 and
5 ml of 1% of solution.
See also Kurarepodobny substances, Muscle relaxants.
Bibliography: The pharmacological basis of therapeutics, ed. by A. G. Gilman a. o., N. Y., 1980. V. P. Fisenko.