Antiarrhymic

Causes G_i-coupled decrease in cAMP.- ↑ K⁺ out of cells → hyperpolarizing the cell and ↓ I_Ca, decreasing AV node conduction.- ↓ SA and AV nodal activity- Affects phase 4 of the action potential, reducing the rate of spontaneous depolarization.

Drug of choice in diagnosing/terminating certain forms of supraventricular tachycardias (SVTs).

- Administered IV, extremely short duration (~15 sec)- Effects blunted by theophylline and caffeine (adenosine receptor antagonists)

Adverse effects: flushing, hypotension, chest pain, sense of impending doom, bronchospasm.