Although PDE5 inhibitors main use has been for erectile dysfunction there has been a great interest in PDE5 inhibitors as a promising new therapeutic agents for treatment of other diseases, such as Alzheimer's disease. Elevation of cGMP levels through inhibition of PDE5 provides a way of improving memory and learning.
PDE5 has also been considered as a potential therapeutic agent for parasitic disease such as African sleeping sickness. Strategic changes were made to the structure of sildenafil so the molecule could project into a parasite-specific pocket (the p-pocket). Similar approach has been used to design therapeutic agents Plasmodium falciparum.