Potent Ca2+ channel antagonist; binds allosterically to the a1-subunit of L-type Ca2+ channels (Kd = 20 pM), at a site distinct from other types of blocker. Shows some selectivity for vascular smooth muscle, inducing vasorelaxation without producing inotropic or chronotropic effects. Inhibits PDGF-stimulated smooth muscle cell proliferation. Purity 99%. MW (observed): 654.77