Kentucky-based Xanodyne Pharmaceuticals has pulled its popular narcotic painkiller, Darvon, from the drug market because it may cause fatal heart rhythms.

Xanodyne Pharmaceuticals has received an approvable letter from the FDA for Zipsor, its lead candidate for the treatment of patients with mild to moderate acute pain.

Florence-based Xanodyne Pharmaceuticals will be adding two often- prescribed pain killers to its portfolio of products. Management received a green light from the U.S.