If you have an erection that lasts more than 4 hours, get medical help right away. An inherited eye disease that affects the retina. When used to treat erectile dysfunction, patients are directed to take the drug once per day, 30 minutes to one hour before their planned sexual activity. Sudden vision loss in one or both eyes can be a sign of a serious eye problem called non-arteritic anterior ischemic optic neuropathy NAION. Administration All forms of the drug are sold as solid oral tablets in doses between 25 and milligrams. Without the stimulation to produce nitric oxide, there is no cGMP build-up and no erection.Viagra is one brand name of a drug that There have also been reports that counterfeit tablets have contained blue printer ink – to give them that genuine Viagra look – illegal . Men will no longer require a prescription to obtain the impotence drug Viagra and will instead be able to buy it over the counter at pharmacies. The decision by the UK . DON’T BE FOOLED BY COUNTERFEIT VIAGRA. VIAGRA is one of the most counterfeited drugs in the world. Counterfeits aren’t just a cheap knockoff of a proven product; they’re .