A drop in the cost of Viagra has led to a rise in the number of private patients using the drug, with further increases expected under plans to amend NHS prescription guidelines.

Pharmaceutical company Pfizer’s patent for Viagra expired in June 2013, allowing other pharmaceutical companies to produce their own version and sending prices plummeting from £21.27 for a pack of four to £1.45.

The British Generic Manufacturers Association (BGMA) said the reduced price has led to more private subscriptions for Viagra, and public use is expected to surge following NHS policy changes.

“Early on there was an increase in private subscriptions, what I think we’ll now see is a significant increase in NHS subscriptions because the NHS can afford to do that now. That’s a direct result of the cost coming down due to generic competition”, said Warwick Smith, director general of BGMA.

The Department for Health is currently reviewing its prescription regulations, as currently only men with set conditions, such as diabetes, multiple sclerosis and prostrate cancer, are entitled to the drug on a NHS prescription.

Consultation research by the Department for Health shows that, thanks to the reduced cost, the NHS will be able to afford Viagra even if demand for the drug trebles.

“If, as we expect, demand significantly increases for example it doubles or even trebles,

the cost of sildenafil products [the active ingredient in Viagra] would be £4 million and £6 million respectively”, said the consultation report.

The consultation also said that making the drug readily available could deter those with erectile dysfunction from the internet.

“Widening the availability of the ED (erectile dysfunction) treatments on the NHS could lessen these risks for patients seeking illegal or unsafe internet supplies”, it read.

Although the consultation said they did not want the NHS to face un-manageable demands from people seeking Viagra “for recreational purposes”, the Department for Health said making prescriptions more widely available would have health benefits.

"Erectile dysfunction is a common and distressing condition. Now that this treatment is much cheaper we can make it more widely available on the NHS and improve thousands of people's self-esteem and relationships”, said a Department for Health spokesperson.