Main Viagra ingredient can make men see BLUE: Doctors warn of strongest dose of impotence pill

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Taking the strongest dose of sildenafil, the main ingredient in Viagra, could make you go colour blind for up to three weeks, doctors have warned.

A small amount of men who take the highest dose of 100mg – the strongest available prescription – may suffer the frightening side-effect for as long as 21 days. 

The warning comes from medics in Turkey who reported a string of patients had visual problems after using drugs containing sildenafil for the first time. 

Seventeen men visited the hospital with abnormally dilated pupils, extreme light sensitivity, prolonged blurred vision or tinted colour-blindness after taking 100mg of sildenafil. There is no suggestion they took Viagra – but sildenafil is the active ingredient in the impotence pill. Pfizer admits that sudden vision loss in one or both eyes is a rare side effect of the drug.

The doctors at Dunyagoz Adana hospital admit that all strengths of the erectile dysfunction drug are safe for the majority of men. 

But they believe a small subset do not break it down properly in the body, leading to high concentrations in the blood even days after it should have been flushed out.

If someone has never taken the drug before then the body is not used to breaking it down. Taking it in such high doses for the first time only gives the body more work to do, the medics say. 

Viagra – the fastest selling drug in history – can be given on prescription or bought over the counter in 25mg, 50mg and 100mg doses.

It works on impotent men by inhibiting an enzyme called phosphodiesterase 5 (PDE5), which widens blood vessels and improves blood flow around the body, including the penis.

But it also halts the production of another enzyme, known as phosphodiesterase type 6 (PDE6), which converts light into sight.

As a result some users report blurred vision that wears off within three to five hours maximum.

But in the recent study, published in Frontiers in Neurology, doctors highlighted the risk of prolonged visual side effects.

Dr Cüneyt Karaarslan noticed a pattern in 17 male patients who attended the Dünyagöz Adana hospital. 

The patients suffered numerous visual disturbances, including abnormally dilated pupils, blurred vision, light sensitivity, and colour vision disturbances, which included intensely blue coloured vision with red/green colour blindness.

All 17 patients had taken sildenafil for the first time, and all took the highest recommended dose of 100mg.

None of the men had been prescribed the medication, but had gone to buy it over the counter.

The visual side-effects began once the drug took effect, and were still present when the men arrived at the clinic 24-48 hours later.

The doctors in the clinic conducted various eye tests and monitored the patients over time to see how their symptoms developed.

Fortunately, in all 17 patients the symptoms had cleared up by 21 days later, but this was doubtless a difficult experience for the men involved. 

Starting with a lower dose may have meant less severe side-effects. 

In addition, taking the drug with medical guidance would likely have meant that the men would not have used such a high dose on their first time.

Dr Karaarslan said: ‘Many men use non-prescription performance enhancing drugs to help with sexual anxiety and erectile dysfunction.

‘For the vast majority of men, any side-effects will be temporary and mild. However, I wanted to highlight that persistent eye and vision problems may be encountered for a small number of users.

‘Although these drugs, when used under the control of physicians and at the recommended doses, provide very important sexual and mental support, uncontrolled and inappropriate doses should not be used or repeated.’

Pfizer, the manufacturer of Viagra, said its not clear if the patients took their product. But the Turkish doctors said they all took sildenafil which active ingredient in the famous blue pill. 

A Viarga spokesperson said: ‘This is a retrospective study where the subjects took 100mg sildenafil (the highest dose) without a prescription (Viagra is only available at 100mg via prescription). 

‘Therefore there is no way of knowing where or how the individuals sourced the sildenafil. 

‘Based on this it is not known whether they took branded Viagra, sildenafil or whether the medicine was obtained from a legitimate source.’ 

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