A number of firms, including Novartis’ generics unit Sandoz, Actavis and Teva’s IVAX division, have been sent warning letters by US regulators over their sales of unapproved headache drugs.

The US Food and Drug Administration has ordered eight manufacturers and 12 distributors to stop marketing several unapproved migraine drugs which contain ergotamine tartrate. A number of headache treatments containing the aforementioned active ingredient have been given the green light by the agency but they carry black-box warnings, while the firms sent the letters are manufacturing and distributing drugs that have not been reviewed.

The unapproved drugs do not carry a boxed warning which the FDA says is required to prevent use of potent CYP 3A4 inhibitors with ergotamine-containing products. “Serious and/or life-threatening ischemia, including fatalities and cases of gangrene, has resulted from such concomitant use,” the agency says, noting that such inhibitors can include certain antibiotics and antifungal treatments, as well as protease inhibitors.

The letters also noted that the companies have 60 days to stop making the drugs and 180 days to halt distributing them, otherwise they will be subject to seizure or injunction.

Deborah Autor, director of the agency’s Center for Drug Evaluation and Research Office of Compliance, said that "doctors and patients often do not realise that not all drugs that are available on the market are backed by FDA approval," noting that it was a priority to get this medicines off the market. However, it is thought that less than 2% of prescription drugs in the USA are unapproved.

The warning letters can be found at www.accessdata.fda.gov/scripts/wlcfm/recentfiles.cfm