Final answer:
The prototypical PDE III inhibitor is sildenafil, which is effective in treating erectile dysfunction but must be used cautiously in men with cardiac issues or those taking nitrates.
Step-by-step explanation:
The prototypical PDE III inhibitor is sildenafil, which was initially investigated for treating hypertension and angina pectoris. Clinical trials showed it was not effective for these heart conditions, but it did prove effective for treating erectile dysfunction (ED). Sildenafil, marketed as Viagra®, was approved by the FDA in 1998 and is reported to be effective in treating approximately 70 to 85 percent of cases of ED. It's important to note that men with cardiac disease taking nitrates should consult their physician before using sildenafil due to potential risks.
In addition to its use in treating ED, PDE inhibitors like sildenafil facilitate the vasodilation signaling pathway in other parts of the vasculature, contributing to their pharmacological effects. Caution is advised for users with health concerns, as certain risks including interactions with other medications and the potential for priapism require medical oversight.