German lawyer Michael Witti and U.S. firm Nagel Rice & Mazie are preparing a class action suit against drugs giant Pfizer over claims relating to its arthritis drug Bextra, Witti said on Sunday.

Pfizer on Thursday agreed to suspend sales of Bextra after U.S. and European regulators said the risk of serious side effects, including a potentially fatal skin allergy, outweighed the benefits.

“We have 12 to 15 persons from Europe claiming that they had skin problems after taking Bextra,” Witti told Reuters by telephone from Munich.

“We expect many more European patients coming forward in the next weeks, but overall numbers will be fairly small.”

Witti said that his U.S. partners had “a few very strong cases, enough to file a class action”. He said the action would be filed in the next few days in New Jersey.

The U.S. Food and Drug Administration said it singled out Bextra for suspension because it gave no added advantage as a painkiller and could cause a potentially life-threatening skin condition called Stevens-Johnson syndrome, an allergic reaction that usually begins as a blistering of the mouth and lips and can spread to the rest of the body.

The U.S. Food and Drug Administration also asked Pfizer to add a “black box” warning - the strongest possible - to the label of its painkiller Celebrex.

Bextra and Celebrex belong to a class of drugs known as COX-2 inhibitors, which also include Merck & Co.‘s Vioxx, a drug withdrawn last year because it increased the risk of Stroke  and Heart attack .

Witti said he was also involved in contributing European cases to a class action suit by the same U.S. law firm on Vioxx.