Differentiation of calcium entry blockers into calcium channel blockers and calcium overload blockers.

The heterogeneity of the several subgroups of calcium-antagonistic drugs requires a rigid and well-defined differentiation of this type of agents. From the chemical point of view verapamil-like drugs, dihydropyridines, benzothiazepines and diphenylalkylamines should be distinguished. Among these largely different groups no obvious relationship between chemical structure and calcium-antagonistic activity can be recognized. Irrespective of the chemical classification all above-mentioned compounds inhibit the entry of calcium into cells. However, from a pharmacological point of view a distinction should be made between calcium channel blockers and calcium overload blockers. Calcium channel blockers selectively and competitively inhibit the transmembranous slow inward current, which is carried by calcium ions both in cardiac tissues and in vascular smooth muscle under physiological conditions. However, calcium overload blockers only inhibit the overload of the cell with calcium ions, which occurs under pathological, ischemic conditions. Finally, a survey is given of the various subtypes of calcium-antagonistic drugs with respect to their organ specificity and therapeutic applicability.