Anoion

Amiodarone Hydrochloride 200 mg Tablet is a white to cream, round, biconvex, uncoated tablet, bisected on one side.
Each tablet contains: Amiodarone (as hydrochloride), BP 200 mg.

Pharmacology: Pharmacodynamics and Pharmacokinetics: Amiodarone is a Class III antiarrhythmic agent prolonging the action potential duration and hence refractory period of atrial, nodal and ventricular tissues, thereby giving a very broad spectrum of activity. An increase in the refractory period of the atrial cells is a major contributing action to the control of atrial tachyarrhythmias.
A reduction in the permeability of the AV node, both anterograde and retrograde, explains the efficacy of the drug in nodal tachycardias caused by re-entry through the AV node. Its action on ventricular arrhythmias is explained by a number of mechanisms. The effect on the atrium and AV node results in a reduction in the frequency of stimuli reaching the ventricle thus giving the ventricular cell mass time to repolarise in cases where there has been desynchronization of the refractory periods. Furthermore, a lengthening of the refractory period of the His-Purkinje system and ventricular contractile fibers reduces or prevents micro re-entry. Amiodarone increases coronary blood flow, decreases cardiac oxygen requirements without producing negative inotropic effects and also suppresses ectopic pacemakers, and this is particularly valuable in arrhythmias associated with ischaemic damage or angina pectoris.
Amiodarone is absorbed variably and erratically from the gastrointestinal tract; the average bioavailability is about 50%, but varies widely, and both the rate and extent of absorption are increased by food. It is extensively distributed to body tissues and accumulates notably in fat as well as in skeletal muscle and highly perfused tissues such as liver, lungs, and spleen; it has been reported to be about 96% bound to plasma proteins. The terminal elimination half- life is about 50 days with a range of about 20 to 100 days due to its extensive tissue distribution. On stopping prolonged amiodarone therapy, a pharmacological effect is evident for a month or more. A major metabolite, desethylamiodarone, has antiarrhythmic properties. There is very little urinary excretion of amiodarone or its metabolites, the major route of excretion being in faeces via the bile; some enterohepatic recycling may occur. Amiodarone and desethylamiodarone are reported to cross the placenta and to be distributed into breast milk.

It is used in the control of ventricular and supraventricular arrhythmias, including arrhythmias associated with Wolff-Parkinson-White syndrome. It has been tried for the prevention of arrhythmias in patients with myocardial infarction or heart failure.

It is given orally in initial doses of 200 mg three times daily for a week, then 200 mg twice daily for a week, and then a usual maintenance dosage of 200 mg or less daily, according to response or as prescribed by a physician.

A case of attempted suicide with 2600 mg amiodarone is reported in the literature. No clinical symptoms, changes in heart rate or blood pressure were reported. The ECG revealed considerable lengthening of the QT interval and T wave inversion in the precordial leads with transient disappearance of R wave in leads V1 to V4, simulating an antero-septal infarction.
In another case of attempted suicide with 8 g amiodarone, the only symptoms reported were profuse perspiration. No signs of cyanosis, dyspnoea or decreased sensitivity were found. No clinical side effects were documented over the monitored period of 3 months. Overdosage may lead to severe bradycardia and to conduction disturbances with the appearance of an idioventricular rhythm, particularly in elderly patients or during digitalis therapy. In these circumstances amiodarone should be temporarily withdrawn and if necessary, beta adrenostimulants or glucagon should be given. In the event of ingestion of a toxic dose, gastric lavage should be employed to reduce absorption and in addition, general supportive measures should be applied.

Amiodarone should not be given to patients with bradycardia, sino-atrial block, AV block or other severe conduction disorders (unless the patient has a pacemaker), severe hypotension, or severe respiratory failure.

It may be used, but with caution, in patients with heart failure. Electrolyte disorders should be corrected before starting treatment. The use of amiodarone should be avoided in patients with iodine sensitivity, or evidence or history of thyroid disorders. Patients taking amiodarone should avoid exposure to sunlight. Thyroid function should be monitored regularly in order to detect amiodarone-induced hyper- or hypothyroidism.

Amiodarone is distributed into breast milk and significant amounts may be ingested if infants are breast fed.
Each 200 mg tablet of amiodarone contains about 75 mg of iodine. The potential effect of this iodine load on the fetus has limited the use of amiodarone in pregnancy since iodine freely crosses the placenta and may cause thyroid disorders in the fetus.

Adverse cardiovascular effects associated with amiodarone include severe bradycardia, sinus arrest, and conduction disturbances. Other adverse effects reported include benign intracranial hypertension, haemolytic or aplastic anaemia, peripheral neuropathy, paresthesias, myopathy, ataxia, tremor, nausea, vomiting, a metallic taste, nightmares, headaches, sleeplessness, fatigue, and epididymitis. Prolonged use of amiodarone causes the development of benign yellowish-brown corneal microdeposits in the majority of patients, sometimes associated with colored haloes of light; these are reversible on stopping therapy.

Amiodarone should be used with caution with other drugs liable to induce bradycardia, such as beta blockers or calcium channel blockers, and with other antiarrhythmic drugs. Use with arrhythmogenic drugs, particularly drugs that prolong the QT interval such as phenothiazine, antipsychotics, tricyclic antidepressants, halofantrine, and terfenadine, should be avoided.

Store at temperatures not exceeding 30°C.

Cardiac Drugs

C01BD01 - amiodarone ; Belongs to class III antiarrhythmics.

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