Assessment of pinacidil in patients with primary Raynaud's phenomenon

In fourteen patients with primary Raynaud's phenomenon we performed a double-blind, controlled study, comparing single doses of 12.5 and 25 mg of the potassium channel opener pinacidil with placebo and the active control nifedipine in randomised order. The main response criterium was the area under the curve (AUC) of the photoelectric plethysmography (PEP) during cooling and rewarming, performed 2-3 hours after administration of the study medication. Single doses of 12.5 and 25 mg pinacidil were shown not to be superior to placebo in respect of the AUC of PEP. Nifedipine, on the contrary, was significantly better than placebo. We conclude that no efficacy can be expected from the potassium channel opener pinacidil in the treatment of primary Raynaud's phenomenon. The efficacy of nifedipine cannot be explained from central rheological effects, as total blood viscosity was the same after pinacidil, nifedipine and placebo.