The vascular effects of flunarizine as compared with those of other clinically used vasoactive substances.

Flunarizine, a difluoro derivative of cinnarizine, produces a long-lasting inhibition of calcium-induced contractions of isolated vascular preparations of rabbit and rat. In this regard it is slightly more active than cinnarizine and markedly more active than papaverine, naftidrofuryl, bencyclane, cylandelate, dihydroergotoxine, xantinol nicotinate and pentoxifylline; calcium dobesilate does not inhibit the calcium-induced responses. A long-lasting antivasoconstrictor effect was observed also for cinnarizine. This action of flunarizine is selective for calcium channels in vascular tissue, since it has little effect on the calcium-induced response of myocardial preparations of the cat. Flunarizine has no effect on the rhythmic activity of myogenically active blood vessels; it thus shows a further selective activity to calcium channels activated by vasoconstrictor agents and not for those opened by intrinsic changes in membrane permeability. This dual selectivity implies that flunarizine is a useful reference substance in assessing calcium antagonism.