US health regulators have said GlaxoSmithKline's Advair medicine is safe and effective for the wider treatment of patients with the lung disease COPD.

The drug is already being prescribed to prevent wheezing and control other symptoms of COPD, chronic obstructive pulmonary disease, but the blockbuster drug will now be prescribed for COPD-related illnesses such as emphysema.

Glaxo's success came as AstraZeneca filed for approval for its own COPD treatment, Symbicort. If Symbicort gets the green light, it will set the stage for a scrap between the UK drugs giants to sell cures for America's fourth-biggest cause of death. In the US alone, more than 12 million suffer from the disease while a further 12 million are probably suffering but without diagnosis, says the National Institutes of Health.

Advair is Glaxo's biggest seller, with 2007 global sales of £3.5 billion.

Food & Drug Administration approval for AstraZeneca could boost Symbicort, which had global sales of £812 million last year.