An erectile dysfunction drug left men with 'intensely blue' vision and red-green blindness

Business Insider US
(Miguel Á. Padriñán, Pexels)
(Miguel Á. Padriñán, Pexels)
  • A hospital in Turkey has treated 17 men in two years who took double the recommended dose of erectile dysfunction drug sildenafil and reported vision problems, including "intense" blue vision.
  • Sildenafil, the active ingredient in Viagra, is one of the most popular drugs in the world, and works by increasing blood flow to the penis.
  • A urologist told Insider that people with erectile dysfunction should always see a doctor because drugs to treat the condition affect everyone differently.
  • For more stories go to

Over a dozen men developed "very intensely" blue vision and other vision changes after taking double the recommended dose of sildenafil, the main ingredient in branded erectile dysfunction treatments like Viagra.

In a case study, researchers examined the reports of 17 men who had visited a clinic in Turkey between August 2017 and March 2019, each within 48 hours of taking 100 milligrams of sildenafil.

The men, who were between 38 and 57 years old, had all taken the pills without doctor's prescriptions, and were trying it for the first time.

According to the report, 12 of the men reported having "very intensely" blue vision, with red-green colour blindness, 13 of the men saw changes in how they perceived colour, and nine felt sensitivity to light. Some also had blurred vision, highly dilated pupils, and issues with depth perception.

Some of them were still dealing with symptoms up to three weeks later before their eyes readjusted.

Erectile dysfunction drugs can have nasty side effects, so always consult your doctor before taking them

The study author, Dr. Cuneyt Karaarslan, director of Dünyagöz Hospital in Istanbul, wrote that it is possible that the men's bodies couldn't process the drug, and that was what caused the negative side effects.

Crucially, they also took double the recommended 50-milligram, which should be enough to treat erectile dysfunction for three to five hours.

"This is why it's necessary to have a doctor review your history and other medications and discuss with you how to use these medications safely," Dr. Jamin Brahmbhatt, a urologist and chief of surgery at South Lake Hospital in Orlando, Florida, told Insider.

"We know sildenafil can cause side effects, some at high rates, some rare. It just validates what we [urologists] already do," Brahmbhatt, who was not involved in the study, added.

"It's best to start at a low dose and titrate up as needed. This way some of the rare side effects - like vision problems - can be avoided."

There have been a few previous studies examining the effect of sildenafil on vision.

One previous study examined the possible damage that sildenafil does to the retina. Dr. Richard Rosen, lead author at that study, wrote that "people who depend on coloured vision for their livelihood need to realise there could be a long-lasting impact of overindulging on this drug." One study examined how 50 mg of the drug could affect healthy men, while another examined the effects of the drug on vision when taken regularly for three months.

Sildenafil works by increasing blood flow to the penis

Sildenafil is one of the world's most popular drugs, and it's also one of the most counterfeited drugs in the world. (Pfizer, a manufacturer of Viagra, had to create its own security force to cut down on the unregulated drugs.)

The drug works by relaxing muscles and arteries in the penis, which then allows more blood to flow to the penis, creating a state of arousal. The drug's effects take about one hour to kick in, and last about three to five hours. Common side effects include headaches, nausea, and dizziness.

A spokesperson for Pfizer, the manufacturer of Viagra, said: "Since its approval in 1998 as a treatment for erectile dysfunction, more than 67 million men around the world have been treated with Viagra. The safety profile of Viagra is supported by more than 74 double blind placebo-controlled clinical studies involving 9,570 patients."

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