Viagra could damage vision in people with an inherited eye disease

Sildenafil, the active ingredient in Viagra, is a phosphodiesterase type 5 (PDE5) inhibitor used to treat erectile dysfunction. The drug also inhibits PDE6, an enzyme in the visual phototransduction pathway, and new evidence indicates that sildenafil may have an adverse impact on retinal function.

Researchers led by Michael Kalloniatis, from the University of New South Wales in Sydney, Australia, evaluated sildenafil in mouse carriers of retinitis pigmentosa. Sildenafil induced a rapid decline in photoreceptor response and a “supernormal” bipolar response, which took two weeks to return to baseline levels.

The findings indicate that sildenafil has direct effects on both the inner and outer retina, say the researchers in Experimental Eye Research (2014;128: 43–56)^[1]
, who note that 1 in 50 people carry recessive traits predisposing them to retinal degeneration.