UPDATE 2-Ipsen's Botox rival faces U.S. marketing delay

* Ipsen, U.S. partner still in talks with FDA on Reloxin

* Original U.S. decision date was April 13

* Analysts say cosmetic, medical OK possible at same time (Adds company and analyst comment, shares, background)

PARIS, April 14 (Reuters) - French drugmaker Ipsen IPN.PA said it is still in talks with the U.S health authority to detail any possible side-effects of its anti-wrinkle treatment Reloxin, signalling a delay in its marketing approval.

The U.S. marketing decision on Reloxin, which could become the sole rival to Allergan's AGN.N Botox, was due after the U.S. Food and Drug Administration in January extended its review of the injectable botulinum toxin product to April 13.

As well as cosmetic use, the neuromuscular blocking toxin is awaiting U.S. clearance for medical use, under the name of Dysport, to treat cervical dystonia, or spasms of the neck muscles.

An Ipsen spokesman declined to indicate when the company expected talks with the FDA to wrap up and when marketing approval of the two drug indications, either separately or possibly at the same time, could be expected.

Ipsen shares rose as much as 1.5 percent earlier on Tuesday before dropping 0.3 percent to 25 euros by 1029 GMT. The DJ health index .SXDP fell 0.8 percent.

“An approval for both Dysport and Reloxin could come around a similar timeframe of mid-year,” PiperJaffray analyst Sam Fazeli said in a research note. “This would be incrementally positive, as it would bring Reloxin’s approval timeline forward by around 3 months on our current expectations.”

Ipsen said last year it hoped to get the U.S. marketing go-ahead for Dysport in cervical dystonia by mid-2009. Some analysts have said they expected Reloxin’s marketing approval to come in the second half of this year.

Dysport is being prescribed in several countries for involuntary eye closure and post-stroke arm spasticity. Ipsen kept the rights for the medical use of Dysport.

For cosmetics use it has a partnership with Medicis Pharmaceutical Corp MRX.N in the United States, Canada and Japan and a partnership with Galderma in Europe. Galderma is a joint-venture between Swiss food maker Nestle NESN.VX and French cosmetics company L'Oreal OREP.PA.

One Paris-based analyst who declined to be identified said the announcement was “neither good, nor bad news” because it looked like the FDA was to give its approval once Ipsen and Medicis detailed the possible side-effects of the drug.

The WebMD website said the most common side effects were headache and eye events, such as drooping eyelids or eyebrows.

Reloxin reduced the appearance of moderate to severe forehead wrinkles and had few side effects in a U.S. trial, a study published last month showed.[ID:nN16528380]

Outside the U.S, the anti-wrinkle treatment is already approved in more than 20 countries, including Britain, under the name of Azzalure. (Reporting by Caroline Jacobs; Editing by Erica Billingham and Rupert Winchester)