The FDA disclosed Tuesday that warning letters were issued to Eli Lilly, Bayer,

Amylin and Cephalon related to alleged violations contained in marketing materials used to promote certain of the companies' drugs

An agency enforcement letter for Eli Lilly's Cymbalta (duloxetine) said a print advertisement for the product, used to treat depression and other disorders, does not adequately communicate risk information. The drugmaker said it is moving to withdraw the materials from circulation.

Separately, Amylin received a warning about Byetta (exenatide) which it co-markets with Eli Lilly for patients with type 2 diabetes. Statements made by Amylin promote the drug for unapproved uses and overstate its efficacy, according to the regulator. Amylin and Eli Lilly said they responded to the concerns and will take the necessary steps "to ensure all product communications adhere to regulatory requirements."

Regarding its warning to Bayer, the FDA said a script for a presentation on Mirena (levonorgestrel), a contraceptive implant, "presents unsubstantiated claims" and overstates the product's efficacy. A spokesperson for the company remarked that the promotional programme was discontinued early last year.

In addition, Cephalon was warned over a promotional card for its lymphoma drug Treanda (bendamustine) that was alleged to be "false and misleading because it omits important risk information."