A recent study has suggested that the erectile dysfunction drug tadalafil, also commonly prescribed for symptoms of an enlarged prostate, may be linked to an increased risk of glaucoma, an eye condition that can cause irreversible vision loss if left untreated. Tadalafil belongs to a class of medications known as phosphodiesterase type 5 inhibitors (PDE5i), which work by relaxing smooth muscles and improving blood flow.

Researchers at National Taiwan University Hospital analyzed medical data from 73,854 men aged 40 and older, half of whom had been prescribed tadalafil or another PDE5i for up to five years between 2012 and 2022 to manage urinary tract symptoms related to an enlarged prostate. The other half had not been prescribed these medications. The study found that men taking tadalafil were approximately 22% more likely to develop glaucoma and 33% more likely to develop the most common form, primary open-angle glaucoma, compared to those not using the drug. Additionally, the group on tadalafil was found to be 32% more likely to develop ocular hypertension, a condition characterized by elevated pressure inside the eye and considered a major risk factor for glaucoma.

Analysis indicated that the increased risk was apparent regardless of how long the drug was taken, with effects observed even after as little as one month of use. The study's authors, publishing their findings in the British Journal of Ophthalmology, noted that chronic inhibition of PDE5 enzymes may affect ocular physiology, though they emphasized that further research is necessary to understand the underlying mechanisms.

While the findings point to a potential association, they do not establish direct causation. Experts caution that other factors common among men prescribed these drugs, such as obesity or high blood pressure, might also contribute to the risk of eye disease. Previous studies have similarly raised concerns regarding drugs like Viagra, another PDE5 inhibitor, but observational study designs limit definitive conclusions.

The researchers underscored that patients should not discontinue tadalafil based on these findings but highlighted the importance of regular eye examinations, particularly for those with pre-existing risk factors such as a family history of glaucoma or nearsightedness. Given that the National Health Service issues nearly five million prescriptions for PDE5 inhibitors annually, primarily for erectile dysfunction, the study calls attention to the need for vigilance in monitoring ocular health among users of these medications.