ED Drug Cialis Linked to Higher Glaucoma Risk When Used for Urinary Symptoms

Cialis (tadalafil) is best known as an erectile dysfunction treatment, but it is also commonly prescribed to men with lower urinary tract symptoms (LUTS), the frequent urination, weak stream and urgency often caused by an enlarged prostate. As a phosphodiesterase type 5 inhibitor (PDE5i), tadalafil works by relaxing smooth muscle, a mechanism that has raised questions about its potential effects on eye tissue, where similar smooth muscle and blood flow dynamics play a role in conditions such as glaucoma.

“Unlike the intermittent dosing regimen commonly used for erectile dysfunction, patients with LUTS typically receive tadalafil on a continuous, daily basis,” explained the research team. “This prolonged exposure may potentially amplify the medication’s cumulative effects on intraocular pressure regulation and ocular blood flow.”

A new retrospective cohort study published in the British Journal of Ophthalmology set out to test whether that theoretical concern shows up in real-world data. Using the TriNetX multinational database, researchers analyzed men age 40 and older with a history of LUTS between 2012 and 2022, excluding anyone with glaucoma before entering the study.

Comparing Nearly 74,000 Matched Patients

The research team compared 36,927 men who used tadalafil against 36,927 men who did not use any PDE5i medication, matching the two groups on age, race, existing health conditions, kidney function and other medications to isolate tadalafil’s specific effect.

Over five years of follow-up, tadalafil use was associated with a 22% higher relative risk of developing glaucoma overall. When researchers broke that risk down by glaucoma subtype, the increases were concentrated in specific categories: ocular hypertension risk rose 32%, primary open-angle glaucoma, the most common form of the disease, rose 33%, and the likelihood of starting glaucoma treatment rose 33%. Notably, no significant increase in risk appeared for low-tension glaucoma or primary angle-closure glaucoma, suggesting the association is not uniform across all forms of the disease.

In absolute terms, 3.93% of tadalafil users developed glaucoma within five years, compared with 3.16% of nonusers, a modest but statistically meaningful difference.

Consistent Findings Across Subgroups

The association held up across several checks researchers use to test whether a finding is likely to be real rather than a statistical artifact. The increased risk remained consistent among men over 50, among White patients, and across various coexisting health conditions. It also stayed stable when investigators built in lag times of one, three and six months between medication use and diagnosis, a technique that helps rule out reverse causation, where an undiagnosed eye condition might have influenced prescribing decisions rather than the other way around.

What This Means for Patients and Doctors

The study’s authors frame the findings as a signal for closer monitoring rather than a reason to avoid tadalafil altogether. They note that ophthalmic evaluation and follow-up may be worth considering for men taking tadalafil for urinary symptoms, particularly those who already have other risk factors for glaucoma, such as family history, age or elevated eye pressure.

Because this is an observational study based on existing health records rather than a randomized trial, it can show an association but cannot definitively prove that tadalafil causes glaucoma. Still, the size of the study population and the consistency of the findings across subgroups add weight to the results.