A PDE5 inhibitor (IC50 = 1.2 nM); selective for PDE5 over PDE1-4 and 7-10 (IC50s = 9.2-280 μM); also inhibits PDE11 (IC50 = 11 nM); decreases production of the proinflammatory cytokines TNF-α, IL-1β, and IL-6 and improves renal function in a rat model of ischemia/reperfusion injury at 10 mg/kg; reduces development of tobacco smoke-induced emphysema and pulmonary hypertension in mice