Some Endo Pharmaceuticals sales material for the Lidoderm pain patch was misleading because it contained unsupported effectiveness claims and omitted important information about risks, U.S. regulators said in a letter released on Wednesday.

The U.S. Food and Drug Administration told the company to immediately stop distributing two direct mail pieces.

The materials “are false or misleading because they make unsubstantiated effectiveness claims for Lidoderm, they omit and minimize serious risk information associated with use of the drug and they inadequately communicate an important limitation in Lidoderm’s approved indication,” the FDA letter said.

Regulators said the materials left out warnings about wearing the patch for too long and omitted advice on how to store and dispose of the product so that it is out of reach of children and pets, which can be harmed by ingesting a new or used patch.

The company also failed to note that Lidoderm should be applied only to intact skin, not broken or inflamed skin, according to the FDA’s letter.

The sales materials were sent to doctors earlier in 2005 and in 2004, Endo spokesman Bill Newbould said.

“We’re working with the FDA to take corrective action,” he said.

Shares of the Chadds Ford, Pennsylvania-based company fell 3 cents to $25.96 in afternoon trading on Nasdaq.