a2-Adrenergic Function in Raynaud's Disease

To the Editor.—  I read with interest the recent review article on Raynaud's phenomenon by Klippel.¹ The author correctly states that we were able to provoke cold-induced vasospastic attacks in patients with primary Raynaud's disease whose digital nerves had been blocked by lidocaine.² However, Klippel's account of our findings on α₂-adrenergic function in Raynaud's disease is incorrect. We performed brachial artery infusions of clonidine hydrochloride (0.25 to 4.0 μg/min) in eight patients with Raynaud's disease and in 11 normal volunteers.³ Patients with Raynaud's disease had significantly greater vasoconstriction than did control subjects at all doses that were administered. These findings were independently replicated.⁴ Lindblad et al⁵ delivered an α₂ agonist by iontophoresis, which perfused only a small area of skin and cannot assure accurate drug delivery.⁵ In contrast, we³ and others⁴ administered clonidine hydrochloride by pump through the brachial