impotency pill that lasts up to eight times longer than Viagra Released...

The cost of an erectile dysfunction pill that lasts up to eight times longer than Viagra has been slashed by half – and could soon be available on prescription on the NHS.

A generic version of Cialis has launched in the UK after the brand's patent ran out, opening up the market for cheaper versions.

As a result, the price of the medication, which has the active ingredient tadalafil, has fallen from £7.22 per tablet to between £2 to £4 per tablet.

Most major online and high street pharmacies – including Superdrug and LloydsPharmacy – are set to stock the generic tablets this month. 

Cialis – along with any branded versions of impotency drugs including Viagra – are not available on the NHS, except in certain circumstances.

But it is now hoped erectile dysfunction sufferers will be able to get the generic version of tadalafil – nicknamed the 'weekend pill' for its longer half life – from their GP in a few months time.

Cialis, or tadalafil, works in a similar way to Viagra, in that it increases the flow of blood to the penis, helping men achieve and maintain an erection. 

However, the biggest difference between the two is the amount of time their effects last.

Viagra remains effective for four to six hours, whereas tadalafil allows you to achieve erections for up to 36 hours after taking a tablet. 

Scott McDougall, pharmacist and director from The Independent Pharmacy, which will stock the new version, said: 'As tadalafil lasts for up to 36 hours, it allows men to have more natural, spontaneous sex lives.

'When Viagra came off patent in 2013, it widened the access to erectile dysfunction treatment for thousands of men.

'Sildenafil [the active ingredient in Viagra] became available on the NHS for the first time – something that may now happen to tadalafil too. A few months' lead time is to be expected.'

Privately, a packet of four 10mg tablets of Cialis costs £28.88 – the equivalent of £7.22 per pill.

Soon the Independent Pharmacy will be stocking it for £14.99 – that's £3.74 per tablet.

Superdrug and LloydsPharmacy have confirmed they will be shortly stocking it but have not yet revealed their prices.