All are toxicities seen with Amiodarone therapy except –
Correct Answer: Productive cough
Description: Ans. is 'd' i.e., Productive cough Amiodarone is a class III antiarrhythmic drug and thus blocks potassium channel. It acts by increasing the action potential duration and effective refractory period.In spite of its present classification as class 3 drug, amiodarone also significantly blocks inactivated sodium channels. It also has weak adrenergic and calcium channel blocking actions.Consequence of these actions include slowing of the heart rate and AV node conduction.Amiodarone is the most powerful antiarrhythmic drug available for the treatment and prevention of both atrial and ventricular arrhythmias.Adverse effect:-Even short term use of Amiodarone causes serious toxicity.Amiodarone accumulates in many tissues which includes heart, lung, liver and skin.Pulmonary toxicityIt is the most important adverse effect.It is dose related. Fatal pulmonary fibrosis may be observed even in low doses.Patient usually presents with cough, chest pain and shortness of breath. Symptoms usually start with dry cough and dyspnoea. Remember, that patients on amiodarone often have dyspnoea attributable to other problems such as heart failure, so amiodarone lung toxicity is difficult to diagnose.Liver toxicityAbnormal liver function and hepatitis develops during amiodarone therapy. (I have not got any documented evidence of liver cirrhosis).Skin depositsSkin deposits results in photodermatitis and gray blue skin discoloration in sun exposed areas e.g. the malar region.Corneal micro depositsCorneal micro deposits are seen in virtually all patients treated with Amiodarone after few weeks of treatment.Sometimes optic neuritis may develop and progress to blindness.Effect of Amiodarone on ThyroidAmiodarone is a potential source of large amount of inorganic iodine and it also blocks the peripheral conversion of thyroxine (T4) to triiodothyronine (T3).Thus Amiodarone may result in hypothyroidism or hyperthyroidism.Thyroid function should be evaluated prior to initiation of treatment and monitored periodically.Cardiac toxicityAmiodarone may produce symptomatic bradycardia and heart block in patients with preexisting sinus or A-V node disease.
Category:
Pharmacology
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