Which medication can cause tachycardia as a side effect?

Epinephrine can lead to tachycardia as a side effect because it is a potent sympathomimetic agent that stimulates the body's fight-or-flight response. When administered, it increases heart rate and myocardial contractility, primarily through its action on beta-adrenergic receptors in the heart. This increase in adrenergic stimulation can cause the heart to beat faster, which is characterized as tachycardia.

While atropine is also associated with increased heart rate, it acts by blocking parasympathetic influences rather than directly stimulating adrenergic pathways like epinephrine does. Amiodarone, on the other hand, is primarily an antiarrhythmic drug that is more often used to manage irregular heart rhythms than to cause an increase in heart rate. Aspirin does not have any significant direct cardiac effects, and it is primarily used as an antiplatelet medication to reduce the risk of blood clots. Therefore, the mechanism by which epinephrine prompts tachycardia clearly distinguishes it as the correct answer in this context.