Low-dose clonidine: a review of its therapeutic efficacy in migraine prophylaxis.

The demonstration that long-term administration of relatively low doses of clonidine decreased the responsiveness of blood vessels to vasodilator and vasoconstrictor drugs in animals led to its investigation in the prevention of migraine in man. Results of placebo-controlled and open therapeutic trials have shown that clonidine in low dosages (75 to 150 mug daily) is useful in preventing migraine headaches in about 30%-50% of patients. A 50% or greater reduction in headache frequency or headache indices has been reported in 40% of patients in controlled and open studies. Thus clonidine, like other drugs used in the interval therapy of migraine, can be expected to be effective in only a proportion of patients. Although clonidine has not been compared directly with other drugs used in the prophylactic treatment of migraine, the general clinical impression is that it is less effective then pizotifen or methysergide. Because it is relatively well tolerated at dosages of 75 to 150 mug daily it is worthy of a trial, particularly in patients considered to need prophylactic migraine therapy for the first time, and when migraine occurs in association with hypertension. At the dosages used in migraine prophylaxis, which are almost invariably lower than used in hypertension, clonidine does not cause hypotension and can be used in patients with cardiovascular disease. The principal side-effects are drowsiness and dry mouth which tend to diminish as treatment continues.