An international team of scientists has found a link between taking tadalafil, a drug prescribed to treat erectile dysfunction and relieve symptoms of an enlarged prostate, and an increased risk of glaucoma. The results of the work were published in the British Journal of Ophthalmology.
Tadalafil, best known under the brand name Cialis, is a phosphodiesterase type 5 (PDE5) inhibitor. Drugs in this group help relax and dilate blood vessels, increasing blood flow to the pelvic organs. According to data provided by ClinCalc, in 2024, about 5 million prescriptions for tadalafil were issued to more than 1 million patients in the United States.
Earlier studies have already linked tadalafil to possible visual impairment. This time, about 74,000 men aged 40 years and older took part in the study. They were divided into two groups: the first included patients who were prescribed tadalafil, the second included men who did not take PDE-5 inhibitors. The participants were monitored for five years.
The analysis showed that those taking tadalafil had a 22% higher risk of developing glaucoma than the control group. They were 32% more likely to have elevated intraocular pressure and 33% more likely to have primary open-angle glaucoma, the most common form of the disease.
Symptoms and other risk factors
Glaucoma is the general name for a group of eye diseases in which increased intraocular pressure can damage structures at the back of the eye, most notably the optic nerve. The disease is the second most common cause of blindness in the world.
Most forms of glaucoma develop gradually and can be virtually asymptomatic in the early stages, meaning that up to 50% of people with the disease in the United States may be unaware of their diagnosis. Possible signs include pain or pressure in the eyes, headache, red eyes, double or blurred vision, blind spots, and loss of peripheral vision. Some forms of the disease, most notably angle-closure glaucoma, can develop suddenly and require emergency medical attention.
The likelihood of developing the disease increases with age: most forms are more common in people over 40, and among people over the age of 75, the disease is estimated to occur in about one in ten.
The risk also depends on heredity and ancestry. Primary open-angle glaucoma is more common in people of African descent, while closed-angle glaucoma is more common in Asians.
Visual features also matter: severe myopia increases the risk of open-angle glaucoma, and farsightedness increases the risk of closed-angle glaucoma. The likelihood of the disease is also higher if close relatives have glaucoma.
Some chronic diseases, such as hypertension and diabetes, are also associated with an increased risk.
The study authors emphasize the limitations of their analysis—the conclusions were drawn solely from observations. Scientists have found a statistical association between taking tadalafil and an increased risk of glaucoma, but the data do not allow us to say that the drug caused the disease. Given the study results, people taking tadalafil long-term, especially if they have other risk factors for glaucoma, are advised to undergo regular examination by an ophthalmologist.
