Authors: Kniotek M, Boguska A PMID: 28316997 PMCID: PMC5337856 DOI: 10.1155/2017/4541958 Abstract Sildenafil, a type 5 phosphodiesterase inhibitor (PDE5-I), is primarily used for treating erectile dysfunction. Sildenafil inhibits the degradation of cyclic guanosine monophosphate (cGMP) by competing with cGMP for binding site of PDE5. cGMP is a secondary messenger activating protein kinases and a common [...]