Tadalafil-d3 is intended for use as an internal standard for the quantification of tadalafil by GC- or LC-MS. Tadalafil is a potent inhibitor of phosphodiesterase 5 (PDE5; IC50 = 1.2 nM). It is selective for PDE5 over PDE1-4 and 7-10 (IC50s = 9.2-280 μM), however, it does also inhibit PDE11 (IC50 = 11 nM). In vivo, tadalafil (10 mg/kg) 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. It also reduces development of tobacco smoke-induced emphysema and pulmonary hypertension in mice. Formulations containing tadalafil have been used to treat erectile dysfunction, pulmonary arterial hypertension, and lower urinary tract dysfunction.
