UK 343-664

UK 343-664 is a **novel, potent analogue of sildenafil** developed by Pfizer as an intravenous, selective **phosphodiesterase type V (PDE5) inhibitor**. It was studied for its effect in **acute pulmonary hypertension**, demonstrating predominant pulmonary vasodilation without significant systemic hypotension. UK 343-664 has greater pulmonary selectivity than milrinone, showing a significant reduction in pulmonary artery pressure and pulmonary vascular resistance in animal models, and displaying efficacy in reversing thromboxane-induced pulmonary hypertension. Its major mechanism is the inhibition of PDE5, resulting in increased cyclic guanosine monophosphate (cGMP) levels and vasorelaxation in the pulmonary vasculature. UK 343-664 is structurally related to sildenafil and was developed for conditions where rapid intravenous pulmonary vasodilation is needed[1][4][6][7].