Cephalon is celebrating after US regulators at last gave the green light to Nuvigil, its new compound for excessive sleepiness and a longer-acting version of its biggest earner Provigil.

The US Food and Drug Administration has approved the non-amphetamine wake-promoting agent Nuvigil (armodafinil) for the treatment of excessive sleepiness associated with obstructive sleep apnea/hypopnea syndrome, narcolepsy, and shift work sleep disorder. The decision comes a year after the FDA delayed approval of Nuvigil over a problem with labelling, which was complicated by the agency's review of another product based on modafinil, Sparlon for attention-deficit hyperactivity disorder.

The latter was rejected on concerns about a child who suffered a serious skin reaction - known as Stevens-Johnson Syndrome - after taking the drug. However, the FDA has now approved final labelling for Nuvigil, which will include a bolded warning about SJS and other skin rashes and hypersensitivity.

Getting the go-ahead for Nuvigil is good news for Cephalon as it will help the firm carry on its dominance of the wakefulness market which has been driven by Provigil (modanafil) which had sales in the first quarter of over $200 million. However, the latter’s patent is scheduled to expire in 2012, while Nuvigil is protected until 2023.

Provigil has been at the centre of some controversy over the past few months and in March, the US Federal Trade Commission subpoenaed the company in March demanding details on agreements signed in 2005 and 2006 with four generic drugmakers – Barr, Teva, Ranbaxy and Mylan – to postpone sales of their copycat versions of Provigil until 2012. Also promotional material for the drug distributed at a public meeting was criticised by the Food and Drug Administration.

However it is all smiles at Cephalon for the moment and chief executive Frank Baldino said that rather than replacing Provigil, “more importantly, we now have a longer-term opportunity to further characterise the utility of this compound beyond wakefulness." In particular, Nuvigil is going to be studied as a treatment in other conditions such as bipolar disorder, cognition associated with in schizophrenia and excessive sleepiness in conditions such as Parkinson's disease and in patients who are being treated for cancer. The company concluded by saying it plans to launch Nuvigil once additional clinical data has been amassed.