The FDA is investigating a possible connection between PDE-5 inhibitors and a form of blindness known as nonarteritic anterior ischemic optic neuropathy (NAION).
The FDA is investigating a possible connection between PDE-5 inhibitors and a form of blindness known as nonarteritic anterior ischemic optic neuropathy (NAION). Patients affected have pre-existing hypertension, diabetes, or hyperlipidemia.
According to news reports, the FDA has 42 cases of blindness 38 among users of sildenafil citrate (Viagra) and four among tadalafil (Cialis) users. The Journal of Neuro-ophthalmology (2005; 25:9-13) published a report of seven cases. Six of the seven patients experienced vision loss within 24 hours after ingesting sildenafil. But Pfizer, the maker of sildenafil, said NAION was not found to be a side effect during the 103 sildenafil clinical trials, which included 13,000 patients.
"There is no evidence showing that NAION occurred more frequently in men taking Viagra than men of similar age and health who did not take Viagra," according to a Pfizer statement.
The company added that outside of clinical trials, 23 million men have taken sildenafil over the past 7 years, and reports of visual field loss due to NAION have been "extremely rare."