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Viagra causes blindness, lawsuits allege.

Viagra, the first oral pill to treat impotence, is facing increased scrutiny amid concerns that it--and other similar treatments for erectile dysfunction--can cause blindness. An ATLA litigation group was formed in August after a report in the March 2005 Journal of Neuro-Ophthalmology detailed the cases of seven men who experienced a form of blindness called non-arteritic ischemic optic neuropathy (NAION) after taking Viagra. Earlier studies also showed a possible link between NAION and the drug.

Viagra (like its competitors Levitra and Cialis) inhibits the enzyme phosphodiesterase (PDE), enabling blood flow to the penis. Although litigation began in earnest after the March report, concerns about Viagra and eye problems have been circulating since the drug was approved in March 1998. In July of that year, the Public Citizen Health Research Group petitioned the FDA to change Viagra's labeling, warning of its potential to adversely affect the retina. The drug's label at the time noted that changes in color perception could result from the drug's effect on the retina.

Unlike that side effect, NAION, commonly called a "stroke of the eye," is a decrease in blood supply to the optic nerve, leading to permanent blindness. The case of Charles Sansone, who took Viagra for years, is typical of lawsuits that allege a connection between Viagra and NAION. One evening in 2002 Sansone took Viagra; when he awoke the next morning, he was unable to see out of one eye. He now is permanently blind in that eye. (Sansone v. Pfizer, No. L-3369-04 (NJ., Camden County Super. Ct. filed June 17, 2004).)

The association between NAION and Viagra was first documented in scientific literature in 1999 and formally noted by a safety evaluator in the FDA's Office of New Drugs in March 2004. That official wrote to her FDA supervisors that Viagra's labeling should include a warning about the "potential increased risk" of NAION in patients with certain risk factors, including hypertension, hypotension, and diabetes.

But, as an investigation this year by Sen. Charles Grassley (R-Iowa) showed, the FDA did not act on that information until May 2005, when it began to discuss with Pfizer a change in Viagra's labeling. In a June letter to the head of the FDA, Grassley noted that internal FDA documents showed that Pfizer "resisted the FDA's initial request to update the Viagra label to include information about NAION risks."

Pfizer has denied any connection between NAION and Viagra. In a May statement, the company said that "a review of 103 Viagra clinical trials involving 13,000 patients found no reports of NAION. Outside of clinical trials, Viagra has been used by more than 23 million men worldwide over the past seven years, and reports of visual field loss due to NMON are extremely rare. There is no evidence showing that NAION occurred more frequently in men taking Viagra than [in] men of similar age and health who did not take Viagra."

Although Viagra is not Pfizer's most profitable drug, it is widely prescribed. Between 2000 and 2003, when Levitra and Cialis entered the market, Viagra enjoyed more than $1 billion in sales per year. In the first six months of this year, the drug accounted for more than $800 million in revenue for Pfizer.

In July, the FDA approved new labels for Viagra, as well as for Cialis and Levitra. The labels note the risk of NMON and that most patients experiencing it "had underlying anatomic or vascular risk factors for developing NMON." Those factors include coronary artery disease, age over 50, diabetes, high blood pressure, high cholesterol, and smoking.

For Greg Jones, an attorney in Wilmington, North Carolina, and a cochair of ATLA's Sexual Dysfunction Drugs Litigation Group, this list of conditions is "significant."

"These are the people who are the major targets of Viagra [marketing]," he said. "They are the people who need Viagra--who it was marketed to--because they have a high risk of developing erectile dysfunction."

Making connections

Viagra's new labeling notes that "it is not possible to determine whether these [NAION] events are related directly to the use of PDE-5 inhibitors, to the patient's underlying vascular risk factors or anatomical defects, to a combination of these factors, or to other factors."

But some research has suggested there is a connection between NAION and Viagra. In a study by the Public Citizen Health Research Group, researchers first looked at the number of adverse events related to ischemic optic neuropathy reported to the FDA for all drugs between January 1998 and December 2004. (The FDA database did not contain the term "non-arteritic ischemic optic neuropathy," so the researchers used the term "ischemic optic neuropathy," which describes a similar condition.)

They found that Viagra had the most incidents, accounting for 48 of 258 reports. The drugs interferon and amiodarone had the next-highest number of reports, with 21 and 12 incidents, respectively. Yet--as Public Citizen later pointed out in an October petition to the FDA seeking the addition of a black-box warning to Viagra's label--although Viagra had no mention of NAION in its label at the time, "the labels for both interferon and amiodarone had prominent warnings."

The researchers then compared the number of cases of ischemic optic neuropathy per million prescriptions in that same time period for Viagra with the number of reports for two statin drugs, Lipitor and Zocor. The researchers compared these numbers because statins, drugs for lowering cholesterol, are likely to be prescribed to a similar group as Viagra--that is, older men who have heart disease, diabetes, or both, which are all risk factors for NAION.

Comparing 89 million prescriptions for Viagra to 380 million for Lipitor, the researchers found that the rate of ischemic optic neuropathy for Viagra per million prescriptions was 18 times higher than that for Lipitor. The rate was even higher for the PDE inhibitor Cialis, although the actual number of cases reported was small and the number of prescriptions was a fraction of Viagra's.

These results are telling, said Sidney Wolfe, Health Research Group director.

Because people taking Viagra would be at higher risk for NAION even if they didn't take the drug, he noted, "people taking Lipitor, who are also at increased cardiovascular risk, should have the same rate of reports of NAION per million prescriptions as people taking these erectile dysfunction drugs. But they don't."

Making connections between Viagra and NAION is vital for Houston attorney Joshua Brockman, who represents Charles Sansone and other men allegedly injured by the drug.

"We've gotten farthest into discovery with [the Sansone] case," he said. "We've gotten some documents, the FDA filings, and the clinical trial information, but we do not have internal memos and e-mails yet. And Pfizer doesn't want to produce those until we come forward with an expert report proving that Viagra is capable of causing ischemic optic neuropathy, and they claim there is no evidence of that."

Brockman has asked the trial judge to order Pfizer to turn over relevant internal documents, citing medical literature supporting Sansone's claims.

"There may be something that makes these people physiologically susceptible to an adverse visual effect with Viagra, and we're just going to have to find out through discovery," he said. "Right now, we haven't been able to determine what Pfizer knew about the relationship between ischemic optic neuropathy and Viagra use."

He added, "I can invalidate an entire defense if I can show they didn't study this."

How many men?

In May, in response to the FDA's investigation of the NAION-Viagra link, Pfizer issued a statement noting that "NAION is the most common acute optic nerve disease in adults over age 50, and it shares a number of common risk factors with erectile dysfunction."

Wolfe said this statement misses the point.

"However common NAION is in people who don't take these drugs, this 18-fold increase in reports per million prescriptions suggests it is much more common in people who do take these drugs," he noted.

But ophthalmologist Frederick W. Fraunfelder, director of the National Registry of Drug-Induced Ocular Side Effects at the Casey Eye Institute in Portland, Oregon, said his registry has no reports of NAION after Viagra use, even though the March study urged doctors to report such cases to the registry. In an October report in the American Journal of Ophthalmology, Fraunfelder noted that "a well-described mechanism" explaining how PDE inhibitors cause ischemic optic neuropathy "does not exist. Since millions have taken these medications with risk factors for ischemic optic neuropathy, this may be an expected coincidence."

Fraunfelder noted in an interview that "if NAION is a real side effect, it's extremely rare," adding that with millions of Viagra prescriptions written, "we only have a small number of NAION cases associated with it."

But, Wolfe countered, some men taking Viagra have other treatment options with no risk of a side effect "as cataclysmic as blindness." He cited a placebo-control trial of Viagra before it was approved, in which about 20 percent of the participants responded to the placebo.

"That means there is a huge amount of psychologically derived sexual dysfunction, as opposed to organic impotence," Wolfe said. "If you are one of these people who has not had psychological help and is taking a drug that would give you the same result as if you were taking a placebo and you are getting blind from it, that's not a good idea."

He also noted that some impotence is caused by medications men take. "Altering the dose of the drugs you are taking or switching to a drug that doesn't cause impotence would be a preferable alternative to going blind," he said.

At press time, seven cases concerning NAION blindness after Viagra use, including Sansone's, were awaiting a November multidistrict litigation hearing in Houston.
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Author:Jablow, Valerie
Publication:Trial
Date:Dec 1, 2005
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