QUINIDINE

From Big Medical Encyclopedia

HINIDYN (Chinidinum) — proti-voaritmpchesky means; dextroizomer of alkaloid of the quinine which is contained in bark of a cinchonic tree. ['-Metoksikhinolil-

(4')] - [5 - in and l x 11 N at to l and d and l - (2) J carbinol; C20H24N2O2.

In medical practice use quinidine sulfate (Chin icl ini sulfas; synonym: Conchicinum siilfuricum, Quini-clini Sulfas). Also Heaney dyne a gluconate (Chinidinum gluconicum) is abroad applied.

Quinidine sulfate — white crystal powder, water soluble (apprx. 1%). On pharmakol. to properties it is close to quinine (see), but also the t of m iches to them and with in about ys in t in and m possesses more expressed anti-and r and.

Mechanism of antiarrhythmic action of X. connect with increase under its influence of the effective refractory period, reduction of amplitude and speed of increase of action potential of fibers of Purkinye and cells of a myocardium, and also with increase in duration of this potential. Besides, quinidine reduces slope of a curve of spontaneous depolarization in Purkinye's fibers and in fabrics, being ectopic pacemakers, reduces threshold action potential (see Bioelectric potential; Heart, physiology). Slows down the speed of carrying out excitement in auricles, an atrioventricular node and in the carrying-out system of heart (see). At the same time in small doses quinidine has m-holinoblokiruyushchee effect and therefore can increase the speed of carrying out impulses on an atrioventricular node. Contractility of a myocardium oppresses and causes dilatation of arterioles. On an ECG at effect of quinidine lengthening of intervals of PQ and QT and expansion of the QRS complex is registered.

After intake from went. - kish. a path 60 — 80% of the entered dose of quinidine are soaked up. In blood to 80% of drug contacts proteins. Time of semi-removal apprx. 6 — 8 hour. In a liver about 70 — 90% of quinidine are metabolized. With kidneys it is allocated apprx. 20% in not changed look. The drugs having properties of inductors of liver enzymes, napr, barbiturates (see) and dipheninum (see), can weaken effect of quinidine. The antiarrhythmic effect develops in 30 min. after administration of drug, and the maximum of effect is observed in 2 — 3 hours.

Quinidine is applied at supraventricular and ventricular forms of arrhythmias, napr, at premature ventricular contraction (see), a Bouveret's disease (see). Drug can be used also for recovery of a sinoatrial rate at patients with a constant form of a ciliary arrhythmia (see}.

Quinidine is appointed inside the adult on 0,1 g of 4 — 6 times a day. At paroxysms of a ciliary arrhythmia it is possible to appoint 0,2 g every 4 hour, and to night — in a dose of 0,4 g. The minimum daily dose — 0,6 g, maximum — 4 g. Treatment is begun with small doses. In the absence of effect and good tolerance of a dose gradually raise.

Side effect is most often shown by nausea, vomiting, a diarrhea, a headache, abdominal pains. In high doses quinidine can cause hypotension (see Hypotension arterial), hemorrhages (owing to oppression of formation of a prothrombin), disturbances of atrioventricular conductivity, deterioration in hearing, sight. Rather seldom at use of quinidine there are allergic reactions (skin rashes, thrombocytopenia, hemolitic anemia, an agranulocytosis). At certain patients of X. can have aritmogenny effect and cause emergence of ventricular tachycardia (see) or fibrillations of ventricles of heart (see). Patients meet an idiosyncrasy to drug therefore its first dose shall be considered as trial for definition of its portability. Purpose of quinidine against the background of therapy by cardiac glycosides is followed by strengthening of the last in blood that can lead to development of intoxication by these drugs. In this regard in need of simultaneous use of quinidine with cardiac glycosides of a dose of the last it is necessary to reduce approximately by 50% in comparison with initial.

Contraindications to use of quinidine are atrioventricular blocks, pregnancy, intoxication cardiac glycosides, the expressed forms of heart failure, an idiosyncrasy to drug. It is necessary to appoint with care it the patient with a sick sinus syndrome, to the persons accepting anticoagulants of indirect type of action and at a myasthenia.

At intoxication quinidine enter Natrii hydrocarbonas. And improvements of atrioventricular conductivity apply noradrenaline or a glucagon to stopping of the hypotension arising at intoxication quinidine.

Form of release: tablets on 0,1 and 0,2 g. Storage: in

the place protected from light.

See also Antiarrhythmic means.

Bibliography: Masur N. A. The general principles of the choice of antiarrhytmic drug and tactics of treatment of patients with disturbances of a heart rhythm, Klin, medical, t. 60, No. 5, page 68, 1982; Volumes of JI. and T about m about in And.

Disturbances of a heart rhythm, the lane with bolg., page 430, Sofia, 1976; Bigger J. T. and. Giardina E. G. Rational use of antiarrhythmic drugs alone and in combination, Cardiovasc. Clin., v. 6, p. 103, 1974; Hoffman B. F., RosenM.R. Wit A. L. Electrophysiology and pharmacology of cardiac arrhythmias, VII. Cardiac effects of quinidine and procaine amide, Amer. Heart J., v. 89, p. 804, v. 90, p. 117, 1975; The pharmacological basis of therapeutics, ed. by A. Gilman and. lake, N. Y., 1980. H. A. Masur.

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