The effect of amiodarone, a new anti‐anginal drug, on cardiac muscle
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It was concluded that amiodarone had effects on cardiac action potentials similar to those which occur after thyroidectomy.Abstract:
1. Amiodarone (2-butyl, 3-(4-diethylaminoethoxy, 3,5-diiodo, benzoyl) benzofuran hydrochloride), an anti-anginal drug which causes coronary dilatation and depresses myocardial oxygen consumption, was found to protect anaesthetized guinea-pigs against ouabain-induced ventricular fibrillation.
2. A 5% (73·4 mM) solution of amiodarone had no local anaesthetic action on guinea-pig skin.
3. Amiodarone, 20 mg/kg (29·4 μmol/kg) given daily for 6 weeks intraperitoneally, had no effect on the resting potential or action potential height, and only a small effect on the maximum rate of depolarization, of isolated rabbit atrial or ventricular muscle fibres as shown by intracellular recording. It caused a considerable prolongation of the action potential in both tissues.
4. Simultaneous administration of thyroxine (5 μg; 6·26 nmol), given daily for 3 weeks intraperitoneally, prevented the prolongation by amiodarone of the duration of the action potential.
5. Treatment of rabbits with 20 mg/kg of amiodarone daily intraperitoneally for 6 weeks had no effect on the weight of the thyroid gland, but was associated with a reduction in body growth rate.
6. Treatment of rabbits with 10 mg/kg (60·3 μmol/kg) of potassium iodide (equal in its iodine content to that of 20 mg/kg of amiodarone), given daily for 6 weeks intraperitoneally, had no effect on body growth rate or the duration of cardiac action potentials.
7. It was concluded that amiodarone had effects on cardiac action potentials similar to those which occur after thyroidectomy.read more
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References
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Journal ArticleDOI
THE EFFECTS ON CARDIAC MUSCLE OF β-RECEPTOR ANTAGONISTS IN RELATION TO THEIR ACTIVITY AS LOCAL ANAESTHETICS
Journal ArticleDOI
The effect of altered thyroid state on atrial intracellular potentials
TL;DR: A group of rabbits was made hypothyroid by thyroidectomy, and another group was injected daily with L‐thyroxine until alterations in thyroid state were confirmed by measurement of heart weight and of plasma iodine.
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Biological comparison of local anaesthetics.
Edith Bülbring,Isabella Wajda +1 more
TL;DR: It was observed that when adrenaline was added to procaine and the mixture was compared with cocaine by the guinea-pig method, the log dose-effect lines became parallel and it was suggested to use procaine as a standard of comparison.
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Pharmacology of amiodarone, and anti-anginal drug with a new biological profile.
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The relevance of β-receptor blockade to ouabain-induced cardiac arrhythmias
TL;DR: In isolated rabbit atria (–)‐, (+)‐ and (±)‐propranolol, and I.C.I. 50172, which has hardly any local anaesthetic activity, greatly reduce the rate of rise of the intracellularly recorded action potential at concentrations which have no significant effect on electrical threshold, contractions, spontaneous frequency, maximum driving frequency, repolarization time or conduction velocity.