Advair, marketed in the UK as Seretide, is drug manufacturer GlaxoSmithKline's most popular asthma drug.
The FDA is now saying that the drug should be given only to patients as a last option and only when other treatments have failed.
Asthma affects an estimated 15m Americans, one third of them children.
Glaxo have issued an angry respopnse and say that the FDA’s move poses a risk to patients because the class of drugs to which Advair belongs is the most effective treatment for asthma.
Kathy Rickard, Glaxo’s vice-president for clinical development, says the proposed labelling changes would reserve the most effective asthma treatment until after a patient has failed on other treatment options and therefore may be at risk of severe outcomes, such as exacerbations and potentially death.
Glaxo does also mention that in July an FDA advisory committee gave a favourable opinion on the drugs, and no new trial data has been published since then.
According to a spokesman for the company in Britain, the drug already carries a “black box” label warning of possible side effects, and the new FDA position on its use simply brings it into line with Europe, but they are surprised and disappointed at the decision.
Analysts predict that the FDA restrictions could have a significant effect on Glaxo’s revenues as the new restrictions, and proposed changes to the drug’s labelling, could severely hamper sales.
Shares in the company are expected to fall sharply.
Advair last year notched up sales of $2.8 billion in America alone, making it the eighth-largest selling branded prescription drug in the country, while worldwide sales of the drug in the same period totalled $4.5 billion.