Ranbaxy Laboratories, India’s largest pharmaceutical company, was yesterday given the green light by US regulators to produce a generic version of Ambien, the most commonly prescribed treatment for insomnia in the US.

Ambien, which is known as Stilnox in some countries, is the second-best-selling drug produced by the French drugs giant Sanofi-Aventis. However, it is set to lose its patent protection next month.

The drug generates annual sales of about $2.12 billion (£1.1 billion) for Sanofi.

America’s Food and Drug Administration yesterday granted provisional approval for Ranbaxy to manufacture a copycat version of the drug, although it has not yet granted it final marketing approval. Ranbaxy said it plans to make the pills for the US market at its factory in Brunswick, New Jersey.

US doctors wrote 57 million prescriptions for insomnia drugs last year.

Ranbaxy is one of India’s most acquisitive companies, having bought eight rivals last year.

It is currently bidding for the generics arm of Germany’s Merck, which is worth an estimated $6 billion. A successful acquisition would make it the world’s seventh-largest maker of generic pharmaceuticals. Israel’s Teva and Iceland’s Actavis are also in the running.

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