Men taking tadalafil, the active ingredient in erectile dysfunction drug Cialis, face a 22 percent increased risk of glaucoma, according to a study published in the British Journal of Ophthalmology.
Researchers analyzed the medical records of nearly 74,000 men aged 40 years and older with lower urinary tract symptoms. The five-year study compared men prescribed the medication to those who did not take it to evaluate their risk of developing glaucoma or increased pressure inside the eye.
The investigation revealed that men on tadalafil were 32 percent more likely to develop high pressure inside the eye than those not taking the drug. They were also 33 percent more likely to develop primary open-angle glaucoma, which is the most common form of glaucoma.
Treatment of prostate and urinary symptoms
Along with erectile dysfunction, tadalafil is prescribed to treat symptoms of benign prostatic hyperplasia, or an enlarged prostate. The medication helps relieve urinary issues such as difficulty starting urination, a weak urine stream, and frequent urination.
Benign prostatic hyperplasia is a non-cancerous condition where the prostate gland enlarges, commonly affecting men as they age. Tadalafil belongs to a class of medications that work by relaxing smooth muscle tissue in the prostate and bladder while dilating blood vessels throughout the body.
Glaucoma and optic nerve damage risks
Glaucoma encompasses a group of eye conditions that cause progressive damage to the optic nerve, which transmits visual signals from the eye to the brain. The damage typically arises from a buildup of fluid and pressure inside the eyeball, which can cause permanent vision loss and total blindness if severe or left untreated.
The study did not posit why tadalafil may increase eye disease risk, but researchers suggested it could stem from altered blood flow to the optic nerve. Tadalafil widens blood vessels and lowers blood pressure to improve circulation for erectile dysfunction, but that process might reduce critical blood flow to the optic nerve during key periods.
In addition, altered blood flow to blood vessels within the eye may elevate intraocular pressure, though investigators noted that this potential mechanism has been less studied.
Ophthalmic evaluation and pre-existing risk factors
Based on the findings, the study authors concluded that men taking tadalafil should undergo regular ophthalmic evaluation and receive medical follow-up care.
Researchers emphasized that the study was observational and did not conclude that tadalafil causes glaucoma. Instead, taking the drug was shown to be associated with an increased risk of the eye disease, particularly for individuals with pre-existing risk factors.
Those pre-existing risk factors include already having glaucoma or elevated eye pressure, having another type of optic nerve condition, or having a family history of glaucoma.
