Vision Problem Added to Labels for Viagra, Cialis, and Levitra

July 18, 2005

Pharmaceutical Executive

Pharmaceutical Executive, Pharmaceutical Executive-07-19-2005, Volume 0, Issue 0

Exactly what is Nonarteritic Ischemic Optic Neuropathy and how might it be linked to the use of ED drugs?

New risks have been added to the labels of the erectile dysfunction drugs Viagra (sildenafil), Cialis (tadalafil), and Levitra (vardenafil). The new labels warn that men over 50 with heart disease, diabetes, high blood pressure, high cholesterol and specific eye problems are at a higher risk of developing a disorder known as Nonarteritic Ischemic Optic Neuropathy (NAION), which can lead to permanent blindness.     Smokers are also at an increased risk, the labeling says.

    A link between NAION and ED drugs may not have been conclusively proven, but the labeling change points out a problem that is likely to become key in evaluating ED products.

What is NAION?

NAION is a strokelike problem that occurs when the blood supply to the optic nerve is altered and usually results in permanent vision loss, said to Dr. Howard Pomeranz of the University of Minnesota Medical School Department of Ophthalmology.

    Pomeranz published a paper on the possible association of NION with users of Viagra in the Journal of Neuro-Ophthalmology in March of this year. He studied seven patients who developed NAION hours after taking Viagra.

What’s the Frequency?

According to spokeswoman Karen Mahoney, FDA has received 43 reports of vision loss associated with the use of erectile dysfunction drugs – 38 for Viagra, 4 for Cialis and 1 for Levitra. The agency based the label changes on reports to its MedWatch system and to the companies marketing these drugs, Mahoney said.

    Spontaneous NAION is very rare. Pomeranz estimated that approximately 1 out of every 10,000 people over the age of 50 develop the disease.

    This estimate jibes with a study cited by Pfizer spokesman Daniel Watts that was published in a 1997 issue of the American Journal of Ophthalmology. The authors of that paper took data from an earlier study on the incidence in two counties and adjusted it for age and sex distribution to determine that NAION occurs at a rate of 10.2 out of every 100,000 people over age 50. Pfizer was not involved in this research, Watts said.

    Based on prescription data, Pfizer believes that 16 million people have used Viagra since the product was launched in the spring of 1998. No data is available on the incidence of NAOIN on known Viagra users over the age of 50.

What’s the Connection?

In an interview, Pomeranz explained that because erectile dysfunction drugs alter blood flow in order to achieve their desired result, it is possible that blood flow to the optic nerve would be affected in people who are susceptible.

    At the same time, “It is unclear whether the reports associated with the drugs are due to the drugs, the patient’s underlying medical conditions, some other factors or a combination of these factors,” Mahoney said via email.

    Pomeranz’s paper acknowledges that people with erectile dysfunction are “more likely to have the microvascular risk factors typically associated with spontaneous NAION.” These risks are associated with vascular problems similar to the factors that can lead to strokes such as diabetes and high blood pressure, he said. FDA acknowledges that it does not know if NAION is caused by erectile dysfunction drugs or by these other vascular problems.

    Pomeranz also noted that spontaneous NAION could occur when someone has a small cup-to-disc ratio (a measurement that helps determine the health of the optic nerve). The ratio is measured by looking at the optic nerve through the patient’s pupil.

    According to Pomeranz, further study on the possible association between erectile dysfunction drugs and NAION should look at the vasculature of the optic nerve.

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