Calcium entry blockers: key issues.

Calcium entry blockers (CEBs) are of widespread interest because of the primary role of Ca2+ in excitation-contraction coupling in vascular smooth muscle and the probable involvement of Ca2+ in the etiology of hypertension. The role of CEBs in the chronic management of essential hypertension, however, has not been established. Key issues are the definition of CEB, mechanism of vasodilator action(s), tissue selectivity, quality of antihypertensive effects, other effects, and future developments. CEBs may have multiple intracellular and extracellular sites of action and may modify both energy production and excitation-contraction coupling in vascular smooth muscle. CEBs are not unique in their vasodilator-antihypertensive profile. Other effects, e.g., coronary vasodilator or cardioprotective effects, of CEBs and their tissue selectivity may, however, provide a favorable benefit/risk profile for their chronic use in essential hypertension. New CEBs may be called modifiers of calcium metabolism, may actually be curative in hypertension, and will most certainly be of major physiological and pharmacological interest.