MCQ on antiarrhythmic agents: Page-5

Antipsychotics like chlorpromazine, haloperidol and thioridazine can increase QT interval in ECG therefore can produce torsade de pointes. Verapamil has no action on potassium channels hence on QT interval.

Adenosine is short acting but rapidly acting. Within 1 to 2 minutes it restores the rhythm to normal sinus rhythm. The usual dose given is 6 mg by rapid IV bolus administration.

Amiodarone cause skin discoloration where skin color changes to slate grey-blue color. Other side effects it produce are pulmonary fibrosis, corneal deposits, optic neuritis and hepatotoxicity. One of the important concern among its side effect is thyroid abnormalities as it can produce either hypo or hyperthyroidism. This is due to iodine moiety present in its structure. Dronedarone is amiodarone derivative that doesn’t produce thyroid abnormality as it lack of iodine in its structure.

Sotalol is both potassium channel blocker as well a beta blocker. Hence it has both class III and class II actions. The beta blocking activity is mainly observed with levo form whereas dextro form mainly block potassium channels. Even selective beta blocker like atenolol are also active in levo form.

Wolf-parkinson-white syndrome is a re-entry type of arrhythmia at AV node. This can lead to atrial fibrillation as impulses are more conducted at atria. Amiodarone can increase the refractory period and hence can decrease the excitability of atrial cells. Verapamil as block AV conduction can further deteriorate the condition hence contraindicated.