The US Food and Drug Administration has given the green light to the first generic versions of Merck & Co's asthma and allergy blockbuster Singulair.

The agency has approved versions of Singulair (montelukast), a leukotriene receptor antagonist, from Apotex, Aurobindo, Endo, Glenmark, Kudco Ireland, Mylan, Roxane, Novartis' Sandoz unit, Torrent and Teva. The latter firm has also got the thumbs-up for its oral granule form of Singulair.

Gregory Geba, director of the Office of Generic Drugs at the FDA's Center for Drug Evaluation and Research, said “for people who suffer from chronic health conditions such as asthma and allergies, it is important to have effective and affordable treatment options". He added that the Singulair generic products approved "will expand those options".

Last week, Merck released its financials for the second quarter and its best-selling treatment was once again Singulair, up 6% to $1.43 billion. Now that it is off-patent in the USA (and will lose patent protection in major European markets in February), the company will be hoping its pipeline will help fill the gap. The firm expects six major filings over the next 18 months, including suvorexant for insomnia and odanacatib for osteoporosis.