DRUGS firm GlaxoSmith-Kline saw little change in its share price yesterday, despite approval in the US of its answer to Viagra.

GSK has been desperate to get its version of the erectile dysfunction tablet, called Levitra, into US pharmacies.

The drug has already been approved in more than 50 countries, but the US was seen as key because it is the world's biggest pharmaceuticals market.

As a direct challenge to Viagra, Glaxo's product gives American men the first alternative in five years to Pfizer's bestseller.

Glaxo admitted in July that sales in Europe, where Levitra was launched in March, had been poor.

The company also faces tough competition on the Continent from Eli Lily's Cialis impotence treatment.

In a statement delivered to the London Stock Exchange, US pharmaceuticals president Chris Viehbacher said Glaxo was delighted with the US Food and Drug Administration's approval and would be educating men and their doctors about its potential use.

Levitra was co-developed and co-promoted with German drugs firm Bayer.

Industry studies have estimated that some degree of impotence affects more than half of all men over 40, and that about 152 million men around the world suffer from the problem.

Glaxo is hoping that the increased use of so-called lifestyle drugs such as Levitra can help it to boost sales at a time when the group is under attack from cheaper copycat versions of its best-selling treatments.

The firm's other products include the antibiotic Augmentin, asthma drug Advair and anti-depressant Paxil.

Pfizer has already filed a US lawsuit alleging that one of its patents would be infringed by the sale of Levitra, but the case remains in its early stages.

Glaxo made British corporate history in May when shareholders, angry at a lucrative "golden parachute" deal for chief executive Dr Jean-Pierre Garnier, voted down the company's remuneration report at its annual meeting.

Shares fell 2p to 1238p by the close of trading yesterday.