<prompt> A drug effect that is produced by therapeutic doses of both timolol and amiodarone is blockade of:Cardiac Na channelsCardiac K channelsBeta adrenoceptorsAlpha-adrenoceptors  <response>: Amiodarone has wide spectrum of antiarrhythmic actions. It acts by all the four mechanisms: blockade of Na channels blockade of b receptors blockade of K channels blockade of Ca2channels. Timolol is a b blocker. Therefore, common action of these two drugs is inhibition of b-receptors. 