It may help you reach the heights of passion, but Viagra could stop you enjoying the pillow talk afterwards. The little blue pills taken by hundreds of thousands of British men may cause deafness, doctors have warned.

Viagra and similar impotence drugs have been linked to hundreds of cases of sudden hearing loss around the world, including some in the UK.

Users in the U.S. are now being warned that the drugs could damage hearing, and the British specialists behind the findings want the same alert to be given here.

The researchers, from Charing Cross, Stoke Mandeville and Royal Marsden hospitals, asked drug watchdogs in Europe, the Americas, East Asia and Australasia if they had received reports of ‘Viagra deafness’ – hearing loss shortly after taking impotence pills.

They uncovered 47 suspected cases of sensorineural hearing loss – a rapid loss of hearing in one or both ears – linked to Viagra and related drugs Cialis and Levitra. Eight were from the UK.

Another 223 reports made in the U.S. were excluded from the study due to lack of detail.

The average age of those affected was 57, although two of the men  involved were only 37, the journal The Laryngoscope reports.

It is not clear how long the problems lasted, but this type of hearing loss, more commonly due to infections and exposure to loud noise, usually causes permanent damage in up to a third of cases.

In a previous study of 29 suspected cases, by the Food and Drug Administration watchdog in the U.S., only a third were classed as temporary.

The FDA advises users of Viagra, Cialis or Levitra who find their hearing suddenly worsening to stop the pills immediately and see their doctor.

The British researchers are not sure how Viagra might affect hearing, but it may be that the chain of chemical reactions it triggers have knock-on effects in the inner ear.

Dr Afroze Shah Khan, of Charing Cross Hospital’s ear, nose and throat department, said: ‘Medical practitioners involved in the prescription of these drugs need to be vigilant about this potential side-effect.’

But Britain’s drugs watchdog, the Medicines and Healthcare Products Regulatory Agency, said complaints of hearing loss linked to Viagra are ‘extremely rare’.

A spokesman added that reports of an adverse reaction to a drug do not prove the medicine caused it.