Lab Study of MQX-503 in Treatment of Raynaud's

The purpose of this study is to determine, in comparison to a placebo control, the response to two dosage strengths of a topical gel formulation of nitroglycerin, MQX-303, in the determination of finger blood flow and skin temperature in the fingers of patients with moderate to severe Raynaud's phenomenon, follwoing exposure to cold temperatures. Blood flow is determined by scanning laser Doppler equipment and skin temperature is measured using attached thermistor probes. Following baseline measurements, the study gel is applied, the hand is placed in a cold chamber, and then blood flow and skin temperature are monitored for the next two hours. Each patient will receive multiple doses on different days so that each can serve as his/her own control in interpreting the response.