Erectile dysfunction (ED) drugs, specifically Viagra (sildenafil citrate, Pfizer) and Cialis (tadalafil, Lilly), cause no vision problems or retinal abnormalities, at least over a six-month period, according to a study in Aprils Archives of Ophthalmology.
ED drugs are known as selective phodiesterase type 5 (PDE5) inhibitors because they treat erectile dysfunction by interfering with the action of the compound PDE5 on the blood vessels in the penis.
However, PDE5 inhibitors may also act on similar compounds in the retina. Mild and transient blurred vision, blue-tinged vision and altered light perception have been reported by men taking these drugs, and some visual complications of long-term use have been reported. Cases of nonarteritic anterior ischemic optic neuropathy (NAION), central serous chorioretinopathy and vascular events have also been linked to ED drugs.
Visual side effects probably occur as a consequence of off-target inhibition of PDE6, which is structurally similar to PDE5 and is involved in regulating phototransduction, the authors say. Visual effects of PDE5 inhibitors are typically mild and transient. However, visual complications of long-term use have been suggested, the authors add. These have been infrequent and of unclear cause because many men who use PDE5 inhibitors have comorbid diseases that predispose them to visual complications, they say.
To further understand the safety of these drugs, researchers at Lilly Research Laboratories, of Eli Lilly and Company, conducted a randomized placebo-controlled study to assess changes in the retina among men taking tadalafil or sildenafil. In the study, 244 male subjects between the ages of 30 to 65 were randomized to take a placebo, 5mg of tadalafil or 50mg of sildenafil daily for six months. Study participants were healthy or had mild erectile dysfunction and had no baseline ophthalmologic abnormalities or risk factors for eye problems.
The results: Among the 194 men (79.5%) who completed the study, no significant differences were found between treatment and placebo groups on electroretinography, visual function tests, measurements of IOP or assessments of the anatomy of the eye.
Our results indicate that there is no cumulative damage or effect of clinical significance for either 5mg of tadalafil or 50mg of sildenafil taken daily for six months, they conclude.
Cordell WH, Maturi RK, Costigan TM, et al; ERG Testing During Chronic PDE5 Inhibitor Administration (ERG-PDE5i) Consortium. Retinal effects of 6 months of daily use of tadalafil or sildenafil. Arch Ophthalmol 2009 Apr;127(4):367-73.
