Sulfoaildenafil is a synthetic chemical compound that is a structural analog of sildenafil (Viagra). Like sildenafil, sulfoaildenafil is a phosphodiesterase type 5 inhibitor. Sulfoaildenafil has been found as an adulterant in a variety of supplements which are sold as "natural" or "herbal" sexual enhancement products. Inhibitors of type-5 cGMP-specific phosphodiesterase (PDE5), such as sildenafil and vardenafil, have been detected in recent years as adulturants in over-the-counter herbal aphrodisiac products and dietary supplements. These compounds have been demonstrated to display PDE5 inhibitory activity in vitro and presumably have similar effects when consumed, but have undergone no formal testing in either humans or animals, and as such represent a significant health risk to consumers of these products due to their unknown safety profile.