Prazosin treatment of primary Raynaud's phenomenon

In a double blind study, prazosin, a specific adrenergic alpha 1-receptor antagonist, or placebo were given to 15 females with primary Raynaud's phenomenon. At a low dose (1 mg twice daily) 5 out of 7 of the prazosin-treated patients reported a reduction of attacks induced by cold (p less than 0.05). This was not confirmed by a cold provocation test which showed no improvement at finger temperatures of 15 or 10 degrees C. The highest tolerated dose in the prazosin-treated patients varied from 2-8 mg daily, and the greatest number of side effects was recorded in this group (p less than 0.05). None of the patients experienced complete relief from cold-induced attacks. It was concluded either that Raynaud's phenomenon is not only caused by stimulation of alpha 1-receptors in digital arteries or the clinically achievable blockade was insufficient to prevent attacks.