Beta blockade causes a mild increase in serum potassium because of blockade of the beta-2-mediated epinephrine activation of the Na Kþ ATPase pump which transports potassium from extracellular fluid into the cells. During stress, serum potassium has been observed to decrease 1.0 mEq/L; this can be prevented by blockade of beta-2 receptors. Nonselective beta-blockers are superior to selective agents in preventing fluctuations of serum potas¬sium concentration during stress and possibly during acute myocardial infarction. It may also be more cardioprotective than cardioselective agents.
Carvedilol has important differences from atenolol, metoprolol, and other beta-blockers. This lipophilic, beta-1, beta-2 blocking agent is a very mild alpha-1 blocker and causes arteriolar dilatation. Antioxidant and antiprolifera-tive properties have also been noted. Carvedilol also lowers plasma endothelin levels.

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