Shares of Cumberland Pharmaceuticals are set to end the week on a major down note after one of the two analysts following the company downgraded his rating.

Michael Tong at Wells Fargo Securities lowered his opinion on Cumberland to 'market perform' from 'outperform' on the basis that a competitor recently received Food and Drug Administration approval to market a product similar to Cumberland's Acetadote, which treats painkiller overdoses. Tong said Innopharma could bring its drug to market soon but added that he expects Cumberland to challenge the launch in court. (The local company did just that earlier this year after New Jersey-based Innopharma challenged its patent for Acetadote.)

As of 1:55 p.m., shares of Cumberland (Ticker: CPIX) were down more than 13 percent to about $4.77. That's their lowest level since the company went public in August of 2009 and takes the market value below $100 million.

Tong said he doesn't expect the stock to bounce back quickly unless the dispute with Innopharma — which received its FDA nod in September — is resolved. Looks like investors are saying that might take a while.