An erectile dysfunction drug that is also used to treat symptoms like sudden urgency and frequency, which are associated with an enlarged prostate in men, may heighten the risk of the serious eye condition, glaucoma, finds a large comparative study published online in the British Journal of Ophthalmology.
The findings prompt the researchers to suggest that patients given tadalafil (Cialis) long term for this indication might need their eye health to be carefully monitored, especially those with glaucoma risk factors, such as family history or existing high pressure inside the eye (ocular hypertension).
Tadalafil, like sildenafil (Viagra), belongs to a class of drugs called phosphodiesterase type 5 inhibitors (PDE5i). These drugs have been associated with various eye health issues, including conditions affecting the optic nerve and the macula—the part of the retina responsible for sharp detailed vision—explain the researchers.
But the evidence linking them to a heightened risk of glaucoma is patchy and inconclusive, particularly tadalafil for the treatment of lower urinary tract symptoms, which typically involves long term daily dosing, they add.
To extend the evidence base, the researchers wanted to find out if tadalafil, a long-acting PDE5i, is associated with heightened glaucoma risk, when prescribed for the management of urinary tract symptoms associated with an enlarged prostate (benign prostatic hyperplasia).
They drew on anonymised data for 73,854 men aged at least 40 in the TriNetX Analytics Network (Global Collaborative Network), half of whom had been prescribed tadalafil or another PDE5i for up to 5 years (between January 2012 and December 2022) to treat their symptoms, and half of whom hadn't been given these drugs.
They assessed how likely both groups of men were to develop glaucoma, ocular hypertension, and to start treatment for glaucoma after 5 years.
The men were paired on the basis of sharing similar potentially influential background features, including age; ethnicity; smoking; alcohol-related disorders; underlying conditions, such as cardiovascular disease, diabetes, cancer, high cholesterol, kidney function; obesity; chronic obstructive pulmonary disease (COPD); and prescribed medications.
Analysis of all the data showed that men prescribed tadalafil were significantly (22%) more likely to develop glaucoma, ocular hypertension (32% more likely), primary open angle glaucoma–the most common type—(33% more likely), and to start glaucoma treatment (33% more likely) than men who hadn't been prescribed tadalafil.
Further in-depth analysis revealed that these associations held true among those who developed glaucoma within 1, 3, or 6 months of starting tadalafil treatment, and were consistently observed among patients aged 50+, those of White ethnicity, and those with various of the underlying conditions included in the study.
This is an observational study, and as such, no firm conclusions can be drawn about cause and effect. The researchers also acknowledge various limitations to their findings: for example, they weren't able to factor in changes in medication prescription and use or the development of other underlying conditions over time.
And most study participants were White, so the findings may not apply to men of other ethnic backgrounds, they add.
Nevertheless, they write: "These findings suggest that chronic PDE5 inhibition may influence ocular physiology, warranting further mechanistic investigation."
But they emphasise: "These findings do not contraindicate tadalafil use but highlight the importance of baseline ophthalmic assessment and regular follow-up, particularly in patients with pre-existing glaucoma, ocular hypertension, a family history of glaucoma, high myopia [short-sightedness], or those requiring long-term therapy."
