Circulating prostacyclin concentrations may be increased by bendrofluazide in patients with essential hypertension.

1. A within-patient randomized double-blind crossover study was performed on mechanisms of action of bendrofluazide in mild essential hypertension. Significant reductions in lying, standing and post-exercise blood pressure were seen after both 3 days and 10 weeks treatment with bendrofluazide (10 mg daily). 2. Plasma levels of 6-oxo-prostaglandin F1 alpha, the chemical hydrolysis product of prostacyclin, were significantly increased by both 3 days and 10 weeks therapy with bendrofluazide. This raises the possibility that thiazides may reduce peripheral resistance by increasing prostacyclin biosynthesis.