Viagra may hurt vision if taken in big doses

Reports of Viagra being used by teens at U.S. rave parties

Publication title: Edmonton Journal
Pages: A3 Section: Top Copy
Publication date: Feb 15, 2001
Dateline: Vancouver
ProQuest document ID: 252928142
Copyright: Copyright Southam Publications Inc. Feb 15, 2001
Author: Fayerman, Pamela


Abstract:

In his studies on mice published in the current Investigative Ophthalmology and Visual Science journal, Dr. Michael Potter states that while the visual side effects of Viagra have already been reported to include a temporary blue cast to what the eyes see and transient hazy vision and increased sensitivity to light, the new research shows that the "potential long-term effect of Viagra (also known as sildenafil) on visual function may not be fully appreciated at this time."

Package insert information in Viagra recommend patients disclose to their doctors whether they have the disease. The Compendium of Pharmaceuticals and Specialties (CPS), a reference text used by pharmacists and doctors, warns that Viagra should be prescribed with caution in patients with RP.

Full text:

New research by a University of B.C. ophthalmologist suggests that the highly popular impotence drug, Viagra, may impair vision, especially in people affected by a common retinal disease.

In his studies on mice published in the current Investigative Ophthalmology and Visual Science journal, Dr. Michael Potter states that while the visual side effects of Viagra have already been reported to include a temporary blue cast to what the eyes see and transient hazy vision and increased sensitivity to light, the new research shows that the "potential long-term effect of Viagra (also known as sildenafil) on visual function may not be fully appreciated at this time."

Potter and co-author Darren Behn's research focused on mice with with a genetic mutation for a disease called retinitis pigmentosa (RP), a common, inherited, degenerative disease which affects at least 1,500 people in B.C. A much larger group of people are healthy carriers of the disease who don't develop symptoms but those who do experience night blindness, loss of peripheral vision and decreased central vision progressing over many years. There are no effective treatments.

Potter said while human studies have not found evidence of long term or permanent damage to vision when taking Viagra, "these studies have either excluded subjects with known visual problems or have been unlikely to include a sufficient number of RP carriers to study this important subpopulation."

Package insert information in Viagra recommend patients disclose to their doctors whether they have the disease. The Compendium of Pharmaceuticals and Specialties (CPS), a reference text used by pharmacists and doctors, warns that Viagra should be prescribed with caution in patients with RP.

In Potter's study, which looked at the effects of Viagra on mouse carriers of RP, twice the recommended dose of the drug resulted in a 50 per cent decrease in visual function, as measured with specialized retinal instruments, and 10 times the recommended dose caused a decrease in visual function of almost 95 per cent. More study is needed to ascertain whether retinal damage is permanent in long-term users of the drug, the study stated.

"There are also reports we are hearing that Viagra is becoming a drug of abuse and that young people are using it at rave parties," Potter said.

Asked why young people would think they'd need an erectile boost, he replied: "Well, there's the old adage that a little is good and more is better. But in this case, it turns out it may be dangerous.