Beta-Sympatholytics (Beta Blockers) - Manual of Medicine
Osmosis from Elsevier - Beta blockers are medications that bind beta adrenergic receptors in both pacemaker cells and non-pacemaker cells, thereby preventing norepinephrine and epinephrine from binding them. Now, Metoprolol belongs to
Antiarrhythmic mechanisms of beta blocker therapy - ScienceDirect
Beta blockers may not help many heart attack victims, research claims | Heart attack | The Guardian