BRISTOL, Tenn. (AP) — Pain drug maker King Pharmaceuticals Inc. said today its profit dropped 53 percent in the second quarter as generic competition eroded sales of its muscle relaxant Skelaxin.

King said its profit fell to $18 million, or 7 cents per share, from $37.9 million, or 15 cents per share a year ago. Excluding one-time costs and gains, the company said it earned 17 cents per share. Revenue dropped to 17 percent to $370.9 million from $445 million.

Analysts expected a profit of 16 cents per share and revenue of $361.1 million, according to Thomson Reuters. Analyst estimates usually leave out one-time items.

Patents supporting Skelaxin were overturned in January 2009, and two companies began selling low-cost generic versions early in the second quarter. Skelaxin sales plunged to $5 million from $102 million a year ago.

The company reported $15 million in revenue from its pain drug Embeda during the second quarter. Embeda reached the market in September.

Sales of King’s bleeding-control drug Thrombin-JMI sales fell 32 percent to $37 million from $49 million, and revenue from its older painkiller Avinza edged down to $25 million from $29 million. Revenue from the Flector painkiller patch edged down to $35 million from $39 million.

King said revenue from its Meridian Auto-Injector business totaled $83 million, up 15 percent from last year. Animal health revenue rose to $85 million from $83 million.

One-time items during the second quarter included a $12.5 million gain on the divestiture of the pain drug Kadian, a $2.5 million loss on extinguishment of debt and $1.8 million in other costs. King’s restructuring costs more than tripled to $4.9 million.

The company also said its research and development costs rose to $33.2 million from $21.2 million.

King confirmed it plans to file a new application for its drug candidate Remoxy during the fourth quarter of this year. It plans to submit a new application for its drug Acurox in first quarter of 2011.