Long-term vasodilator treatment with flosequinan does not lead to hemodynamic tolerance or neurohormonal activation in severe heart failure.

Flosequinan is a balanced-type vasodilator with a prolonged mode of action due to an approximate 38-hour half-life of its active first metabolite, BTS 53554. As this may lead to tolerance and neurohormonal activation, the acute and long-term pharmacokinetic, hemodynamic, and neurohormonal profile of flosequinan was evaluated. On three consecutive days, 23 patients with heart failure (New York Heart Association classes II-IV), despite digitalis and diuretics, underwent invasive hemodynamic studies after receiving 100 mg oral flosequinan (day 1), placebo (day 2), and 100 mg flosequinan (day 3), followed by repeat invasive evaluation after long-term flosequinan (100 mg daily) for 17 +/- 2 weeks. On each study day, plasma flosequinan levels increased to 1.9 +/- 0.2 mg/L after 1 hour, but returned to baseline levels at 24 hours. In contrast, BTS 53554 increased progressively, reaching relatively high plateau levels (6 mg/L) during chronic therapy. First-dose flosequinan decreased the pulmonary wedge, right atrial pressure, and systemic resistance by 50, 60, and 22%, respectively, whereas the cardiac index was increased by 40%; these effects lasted for 48 hours. During long-term treatment, baseline values of the pulmonary wedge and right atrial pressure were comparable to prestudy values, whereas systemic resistance had decreased by 22%, and the cardiac index and heart rate had increased by 22 and 14%, respectively. Readministration of flosequinan did not further affect hemodynamics, apart from a moderate reduction in the pulmonary wedge and right atrial pressure. Neurohumoral activation did not occur during acute or long-term therapy. Thus, although changes in left and right heart filling pressures are attenuated during long-term treatment, flosequinan induces sustained arterial dilatation and improves cardiac pump function without activation of circulating neurohormones.