It was reported that on 86 patients with moderate to severe idiopathic restless leg syndrome who were randomized to placebo or to 0.5, 1.0, or 2.0 mg of cabergoline (Dostinex) in the evening in a five-week double blind dose-finding study.
All three doses of cabergoline proved effective at reducing restless leg syndrome severity at night, which was the primary study end point. Both the 1mg and the 2mg dose reduced this end point by five points on a 10 point standardized restless leg syndrome severity scale. The 0.5mg dose was nearly as effective at bringing nighttime relief. The 2mg evening dosage, however, was significantly more effective at relieving symptoms over a full 24 hours. More than 40 percent of patients randomized to this dosage indicated they were totally symptom-free at five weeks, compared with 25 percent on 1mg/day, slightly fewer on 0.5mg and less than five percent of patients in the placebo group.
Cabergoline-treated patients rated the quality of their sleep as greatly improved, with fewer and much briefer episodes of awakening than the placebo group. Side effects of cabergoline consisted of mild nausea, dizziness, itching, and constipation occurring with a frequency only slightly greater than that seen in the placebo group. Cabergoline is a dopamine D2 agonist with a very long half-life: In excess of 65 hours. As a potent inhibitor of prolactin secretion, the drug is prescribed for the management of hyperprolactinemia-related disorders. It is also used in patients with Parkinson’s disease, either early in the course of the disease in order to delay the use of levodopa or later when levodopa becomes ineffective or poorly tolerated. Because cabergoline is effective for the control of abnormal movements in Parkinson’s disease, co-investigators decided to study the drug in patients with restless leg syndrome, a troublesome disorder of obscure etiology. The new double-blind randomized German trial sponsored by Pharmacia Corporation, followed an earlier favorable open-label nine patient pilot study.