The first medicine for depression formulated using a transdermal patch has been approved by the US Food and Drug Administration.

Emsam (selegiline) was developed by Bristol-Myers Squibb and Somerset Pharmaceutical, a joint venture between Mylan Laboratories and Watson Pharmaceuticals. The active ingredient in the product is a monoamine oxidase inhibitor that has been shown to relieve symptoms in patients with depression.

The product was delayed on the way to market because of discussions with the FDA about labelling for the drug, particularly with regard to dietary restrictions for foods rich in tyramine, an amino acid found in dairy and meat products.

All existing drug products based on selegiline carry dietary warnings because if patients ingest too much tyramine while taking them they can suffer dramatic elevations in blood pressure. Emsam has been approved with no dietary restrictions on the starting and target doses of 6mg/24 hours, although these do kick in if the 9mg/24 hour and 12mg/24 hour doses are used.

“Emsam provides a significant advance because at least in its lowest dose patients can use the drug without the usual dietary restrictions associated with these types of drugs known as MAO inhibitors,” commented Dr Steven Galson, director of the FDA’s Center for Drug Evaluation and Research.

Selegiline is used to treat Parkinson’s disease, but the need for dietary restrictions has meant that it is used only sparingly in patients with depression, typically for those with hard-to-treat symptoms. The patch will change that, providing an additional treatment option for patients, although some analysts expect Emsam to be a niche product with limited sales potential, with estimates typically in the $50 million to $100 million range.