prominent consumer advocacy group is calling for the government to add the most serious of warnings to the labels of Viagra and other impotence drugs, noting that some users have gone blind. Public Citizen petitioned the Food and Drug Administration Thursday to add black-box warnings to the labels of Viagra, Cialis and Levitra, as well as the hypertension drug Revatio, which is similar to Viagra.A small number of people taking the impotence drugs have developed NAION, or non-arteritic ischemic optic neuropathy, a loss of vision that is frequently irreversible.
