Ingredient in erectile dysfunction and prostate drug linked to eye disease that causes blindness, study suggests

A popular drug used to treat erectile dysfunction and symptoms of an enlarged prostate may increase the risk of a serious eye disease that can lead to blindness.

Tadalafil, the active ingredient in the brand name erectile dysfunction drug Cialis, may be associated with an increased risk of glaucoma, a serious eye condition that can gradually cause vision loss.

Researchers analyzed the health records of nearly 74,000 men 40 years and older with lower urinary tract symptoms. 

Along with erectile dysfunction, tadalafil is also used to treat symptoms of benign prostatic hyperplasia (BPH) or an enlarged prostate, to help relieve urinary symptoms such as difficulty starting urination, weak urine stream, and frequent urination.

The study, published in the British Journal of Ophthalmology, compared men prescribed the drug to men who did not take it and followed them for five years to determine if they had developed glaucoma or increased pressure inside the eye, which can also lead to vision problems.

Researchers found men on tadalafil were 22 percent more likely to develop glaucoma than men who did not take the drug. 

They also found men taking the medication were 32 percent more likely to develop high pressure inside the eye and 33 percent more likely to develop primary open-angle glaucoma, the most common type of glaucoma. 

Glaucoma is a group of eye conditions that damage the optic nerve. It typically occurs because of a buildup of fluid and pressure inside the eye. If it goes untreated or is severe, it can lead to permanent vision loss and blindness. 

Based on the findings, the study authors concluded that men taking the drug should undergo ophthalmic evaluation and receive follow ups.

The study didn’t posit why tadalafil may increase risk but it could be because it changes blood flow to the optic nerve. 

Tadalafil widens blood vessels and lowers blood pressure. While this helps with circulation when it comes to erectile dysfunction, it could reduce blood flow to the optic nerve during critical times.

Additionally, a change in blood flow to blood vessels in the eye may raise eye pressure, though this link has been less studied.

The study was observational and researchers did not conclude that tadalafil causes glaucoma, only that taking it may be associated with increased risk of the eye disease, especially in people with pre existing risk factors. 

These risk factors include already having glaucoma or increased eye pressure, having some other type of optic nerve condition and having a family history of the eye disease.