Effect of flunarizine on pituitary secretion by healthy men and in woman with migraine.

Flunarizine is widely used in the prophylaxis of migraine. It is both a calcium blocker and a histamine antagonist at H1-receptors and either of these effects could alter hormonal secretion. The effect of administration of flunarizine to 8 women with common migraine on pituitary secretion has been studied. The dopamine antagonist domperidone (10 mg) and gonadotropin releasing hormone (100 micrograms) were injected iv before and after one month of flunarizine therapy (10 mg orally at bedtime). The basal prolactin level was significantly increased by the drug, and the peak induced by domperidone stimulation was reduced. Basal TSH concentrations were not affected, but the increase after domperidone was blunted. After 90 days of therapy there were no significant differences from the baseline concentration. Neither basal nor gonadotropin releasing hormone-stimulated secretion of FSH and LH were affected by flunarizine. Twelve healthy men were given placebo and flunarizine (10 mg at bedtime) for 5 days in single-blind fashion. Flunarizine caused a significant increase in prolactin and TSH with no effect on basal gonadotropin and thyroid hormone levels. These results can be accounted for by the calcium blocking effect of the drug, although weak interference with dopaminergic transmission is a further possibility explanation.