Flunarizine is a 'selective'
calcium entry blocker with a similar chemical structure and pharmacological profile to the related compound,
cinnarizine. However, in contrast to
cinnarizine it has a long plasma half-life and need only be given once a day. The majority of therapeutic trials in the prophylaxis of
migraine, occlusive
peripheral vascular disease and
vertigo of central or peripheral origin have been placebo-controlled, and have shown that the
drug produces significantly greater beneficial effects than placebo as evaluated by subjective and objective criteria. A small number of comparative studies have shown
flunarizine to be at least as effective as
pizotifen in
migraine prophylaxis, and in a longer term study as effective as
cinnarizine in
vertigo of central origin. However, it has not been compared with other drugs which may be useful in these areas, such as
methysergide in
migraine prophylaxis, some
antihistamines or
phenothiazines in
vertigo, or (understandably at this stage of its evolution) with surgical revascularisation in severe occlusive
peripheral vascular disease. In preliminary placebo-controlled studies there was some evidence that
flunarizine may improve impaired cognitive function in patients with
cerebrovascular disorders, but such findings need further confirmation in additional carefully conducted studies. With a very long half-life,
flunarizine may be given once daily; and drowsiness, the main side effect, can be minimised by taking the daily dose in the evening. Thus, it appears that
flunarizine will offer a useful alternative in some therapeutic areas that can be difficult to manage with previously available
therapy. However, a definitive statement on its relative place in
therapy of such conditions must await a few well-controlled comparative studies.