Men who take tadalafil — the drug sold under the brand name Cialis for erectile dysfunction and enlarged prostate symptoms — are 22% more likely to develop glaucoma than men who do not take the medication, according to a major new multinational study of nearly 74,000 patients published in the British Journal of Ophthalmology, raising new questions about long-term safety risks associated with one of the most widely prescribed drug classes in the world.
An international research team analyzed health records from 73,882 men aged 40 and older with lower urinary tract symptoms — a population that frequently uses tadalafil for enlarged prostate in addition to its better-known erectile dysfunction indication — comparing roughly 37,000 men prescribed tadalafil against a similar group who did not use drugs in the phosphodiesterase type 5 inhibitor class. Researchers tracked participants for up to five years, looking specifically for new glaucoma diagnoses, elevated intraocular pressure, and whether patients required treatment for glaucoma. The tadalafil group showed a 22% higher risk of developing glaucoma compared to the control group, with the association remaining statistically significant after adjusting for known risk factors including age, diabetes, hypertension, and other conditions linked to both glaucoma and erectile dysfunction.
"Men taking tadalafil — or any PDE5 inhibitor — should make sure their eye doctor knows what medications they are on, and should report any changes in vision promptly. This is a manageable risk if caught early, but glaucoma that goes undetected can cause permanent damage." — Ophthalmology researchers, British Journal of Ophthalmology
Glaucoma is not a single condition but a group of eye diseases that damage the optic nerve — most commonly through elevated pressure inside the eye — and progressively narrow a patient's visual field, ultimately leading to blindness if left untreated. It is the second-leading cause of blindness worldwide. The insidious quality of glaucoma is that it causes no pain and very gradual vision loss, meaning many patients do not notice symptoms until significant and irreversible damage has already occurred. Early detection through regular eye pressure testing and optic nerve evaluation is the primary defense. The new research suggests that men taking tadalafil long-term may benefit from more frequent ophthalmological monitoring than the general population.
The biological mechanism by which tadalafil might increase glaucoma risk is not fully established. Tadalafil works by relaxing smooth muscle and dilating blood vessels through inhibition of a specific enzyme — the same mechanism that makes it effective for erectile dysfunction and urinary symptoms. Researchers hypothesize that this vascular effect may alter blood flow dynamics within the eye in ways that affect optic nerve perfusion or intraocular pressure regulation over time. The study does not establish causation — it identifies an association — and the researchers acknowledge that men with erectile dysfunction or enlarged prostate may have underlying vascular health profiles that independently elevate their glaucoma risk.
Tadalafil is one of the most widely prescribed drugs in the world and is available in both brand-name (Cialis) and generic forms. It belongs to the phosphodiesterase type 5 inhibitor class, which also includes sildenafil (Viagra), vardenafil (Levitra), and avanafil (Stendra). Prior research has linked the PDE5 inhibitor class to other eye conditions including non-arteritic anterior ischemic optic neuropathy, a sudden and often irreversible vision loss caused by interrupted blood flow to the optic nerve. Men who experience sudden vision changes while taking any PDE5 inhibitor should stop the medication and seek immediate medical attention.
This study does not mean men should stop taking a medication their doctor has prescribed without discussing it first. What it means is that men on long-term tadalafil therapy should make sure their prescribing physician knows to flag eye health as a monitoring concern, and should ensure they are getting regular eye exams with intraocular pressure measurements. Glaucoma caught early is treatable. Glaucoma that advances undetected causes damage that cannot be undone. A 22% elevated risk is not alarming in isolation — but it is information that belongs in the conversation between a patient and his doctor.