NEW YORK (TheStreet) -- Horizon Pharmaceuticals (HZNP - Get Report) plummeted Monday after the company said CVS Caremark (CVS - Get Report) and Express Scripts (ESRX - Get Report) would put Horizon's two best-selling drugs on their exclusion lists at the beginning of 2015.
The move to the exclusion list means patients would incur more of a cost for the drugs unless they switch to cheaper alternatives. CVS and Express Scripts are the largest and second-largest pharmacy benefit managers in the U.S.
The two drugs are Duexis, which treats arthritis pains for those with stomach issues, and Vimovo, which treats osteoporosis and rheumatoid arthritis. Horizon acquired the U.S. rights to Vimovo from AstraZeneca (AZN - Get Report) in November.
Horizon, which disclosed the news in a regulatory filing, said the exclusions should not affect 2014 guidance but said nothing about next year; however, the company noted 20% to 30% of Duexis and Vimovo prescriptions could be affected.
For more on this story, read TheStreet's Adam Feuerstein's article here.
The stock was down 33.74% to $9.21 at 2:23 p.m. More than 11.8 million shares had changed hands, compared to the average volume of 2,857,670.HZNP data by YCharts