The drugs named calcium channel blockers (CCBs) were initially termed
cal- cium antagonists (see Chapter 1). They are also designated as
calcium entry blockers (CEBs), calcium blockers, calcium channel
antagonists, calcium channel inhibitors (and in French anticalciques).
As this is reported in several chapters of this book, their main effect
is a blockade of calcium entry into cells through voltage operated
calcium channels (VOCCs). Chemically related drugs, such as Bay K 8644,
exert the opposite effect by increasing the proba- bility of calcium
channel opening. One of the subcommittees of the Nomenclature Committee
(NC-IUPAR) of the International Union of Pharmacology has been devoted
to the classification of calcium channels and the site of action of
drugs modifying channel function. The members of this Committee are
noted for their significant contribution to the field (Tab. 1). A report
has been published in 1992 in Pharmacological Reviews [3]. A list of
criteria was approved for the identification of distinct drug binding 2
sites on Ca + channels. It included: (a) the demonstration of a
stereoselective binding site supported by drug interaction studies
(competition with other drugs, non-competitive interactions with other
sites, reversal of inhibitory effects by channel activators); (b)
demonstration of the electrophysiologieal effects of the drug and
selectivity of action compared to other sites; (c) deter- mination of
the affinity for the type and subtype of ion channel. These criteria
have identified different classes of Ca antagonists (see Chapter 2).
