Two Case Reports of NAION in Canada Prompt Drug-safety Alert on ED Drugs

On July 26, 2005 Health Canada advised users of the erectile dysfunction drugs Viagra, Cialis, and Levitra to seek "immediate medical attention" if they experience sudden vision loss or other vision problems when taking any one of these drugs.

Health Canada is reviewing two Canadian reports of Viagra users who developed non-arteritic anterior ischemic optic neuropathy (NAION), a specific type of vision loss, after taking one of these erectile dysfunction (ED) drugs, also known as impotence drugs. Health Canada expressly stated that it did not know if the vision problem NAION is linked to the ED drugs, as regards the two Canadian case reports, or otherwise.

Earlier in July 2005 the FDA approved new labeling to warn men about possible blindness from Pfizer Inc.’s Viagra. The FDA action on the Viagra warning label also affects Cialis, sold by Eli Lilly & Co. and Icos Corp., as well as Levitra, which is co-promoted by GlaxoSmithKline and Bayer AG .

Health Canada’s spokeswoman, Nathalie Lalonde, said it was too early to say whether Health Canada would follow the FDA’s lead as regards the Viagra warning label revision. "We anticipate that we will be in a position to make a decision in terms of labeling changes within the next two to three months," she said.

The July 2005 Health Canada advisory on the possible association between NAION and ED drugs provides some useful information about symptoms of NAION and risk factors for NAION:

The specific type of vision loss, called nonarteritic anterior ischemic optic neuropathy (NAION), occurs when blood flow to the optic nerve is blocked. It causes sudden and painless loss of vision in one or both eyes. Those who experience one episode are at a greater risk of experiencing a second episode affecting the other eye. Vision loss may be partial or complete. While in some cases the condition may improve over time, it can also be irreversible. Risk factors for NAION include: age greater than 50 years; heart disease; high blood pressure; high cholesterol; diabetes; smoking; and, certain pre-existing eye problems.

Health Canada says it has requested additional drug-safety information from all three manufacturers – Pfizer (Viagra), Eli Lilly (Cialis), and Bayer AG/GlaxoSmithKline (Levitra).

(Posted by: Tom Lamb)