A report surfaced two months ago that seven patients taking Viagra had fallen victim to nonarteritic ischemic optic neuropathy (NAION). This stroke of the eye takes place when blood flow is cut off to the optic nerve, injuring the nerve and causing permanent vision loss. Not, surprisingly, the number of men stricken with NAION has grown, prompting an investigation by the FDA.

So far, the FDA has collected 43 reports of varying degrees of vision loss from patients taking Viagra (38), Cialis (4) and Levitra (1), and drugmaker Pfizer has received 23 reports of such side effects since Viagra was introduced in 1998.

As a result, Pfizer is currently negotiating with the FDA to add an advisory about that “blindside” effect on Viagra’s label, probably pretty similar to the one added to Cialis earlier this month. It’s certainly bad timing for Pfizer, considering first-quarter sales of Viagra — the world’s best-selling erectile dysfunction drug with 68 percent of the market — had risen 5 percent to $438 million.

Makes you wonder if recent numbers by GlaxoSmithKline (Levitra) estimating more than 50 percent of the impotence pills on the market last year were samples was indeed way too low.

Bloomberg.com May 27, 2005

USA Today May 27, 2005