Possible involvement of dopaminergic mechanisms in the antimigraine action of flunarizine

Flunarizine, a calcium antagonist widely used in the prophylactic treatment of migraine, may interfere with dopaminergic systems. Flunarizine therapy can in fact induce extrapyramidal side effects and can increase basal as well as stimulated prolactin levels. To better define the mechanism of flunarizine action in migraine, we studied prolactin and growth hormone responses to thyrotropin releasing hormone and sulpiride in 13 female migraineurs before and after 60 days of flunarizine therapy. The treatment did not modify basal prolactin and growth hormone levels, but prolactin response to thyrotropin releasing hormone was enhanced. A paradoxical increase of growth hormone to thyrotropin releasing hormone observed before therapy was blunted after flunarizine treatment. These data indicate a modulatory action of flunarizine on dopaminergic systems which might to some extent explain the antimigraine action of this drug.