Effect of thromboxane synthetase inhibition in Raynaud's phenomenon

To determine whether thromboxane A2 may be of pathogenetic importance in Raynaud's phenomenon, finger hemodynamic and clinical responses to dazoxiben, a thromboxane synthetase inhibitor, were studied in 25 subjects. Thirteen subjects had idiopathic Raynaud's disease and 12 subjects had secondary Raynaud's disease. A double-blind, 2-week crossover study design was used. Dazoxiben dose was 100 mg four times a day. Total fingertip blood flow (FBF) by venous occlusion plethysmography, fingertip capillary flow (FCF) by radioisotope disappearance rate, and finger systolic blood pressure (FSP) were measured in a 28.3 degree and a 20 degree room at the end of each period. Subjects kept diaries of vasospastic attacks. For the 25 subjects and the two subgroups, dazoxiben did not improve total FBF, FCF, or FSP. Subjects with idiopathic Raynaud's disease had a small decrease in the number of vasospastic attacks and an increase in percentage of attack-free days on dazoxiben, but in an overall evaluation by the subjects in both subgroups, dazoxiben did not improve symptoms. It is concluded that thromboxane is not of pathogenetic importance in Raynaud's phenomenon and that thromboxane synthesis inhibition is not of therapeutic benefit.