Clinical efficacy of flosequinan in heart failure. The effects of the new arterial and venous vasodilator flosequinan have been evaluated in a variety of ways in different groups of patients with chronic heart failure. Flosequinan improved the central hemodynamic effects of heart failure in one group, with benefits still apparent up to 24 hours after a single oral dose. In another group it also improved calf blood flow and, therefore, blood flow to skeletal muscle. Also, using a number of different tests, it improved the exercise performance of the patients. In a further group the improvement in exercise tolerance produced was similar to that of captopril. Flosequinan has the necessary properties of a drug that is likely to be of benefit in the treatment of patients with chronic heart failure. 