A potential rival to Irvine-based Allergan Inc.’s Botox wrinkle-reducing drug is facing a delay.

Ipsen SA, a French drug maker, said Tuesday that it was still in talks with the Food and Drug Administration to detail any possible side effects of Reloxin.

The FDA was due to make a marketing decision on Reloxin after extending its review of the injectable botulinum toxin product in January to April 13.

Medicis Pharmaceutical Corp. of Scottsdale has the domestic cosmetic rights to Reloxin. Ipsen has the therapeutic rights to the drug and is using the Dysport name for it.

An Ipsen spokesman declined to say when the company expected talks with regulators to wrap up and when marketing approval for Reloxin and Dysport, according to Reuters.

Some analysts had expected Reloxin’s marketing approval to come in the second half of this year.

Allergan, in the meantime, has been preparing for competition, including hosting a Web seminar where it emphasized that Botox and Reloxin are not interchangeable.

Investors didn’t seem to worry – shares of Allergan and Medicis were essentially unchanged in midday New York stock trading.