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La Jolla Pharmaceutical Co. (LJPC - Get Report) took a pounding Monday, with the stock plunging more than 46% on the heels of disappointing sales projections for its key drug Giapreza.

La Jolla's share price fell to $5.64 by 2:34 pm, down from its close of $10.52 on Friday, after the company said it expects sales of low blood pressure drug Giapreza to hit $24 million-$28 million in 2019, roughly half of what analysts had projected.

The pharmaceutical company's stock has been trending downward since late September, when it was trading at more than $22. 

La Jolla reported a 20% increase during the fourth quarter in sales of Giapreza, first launched in March, with sales of the drug, used to increase blood pressure in patients suffering from septic or distributive shock. Sales of the drug are expected to total $10.1 million for 2018.

The company said it has $172 million in cash, with operating activities in 2019 expected to cost from $89 million to $94 million.

"We believe that Giapreza has the potential to help many patients suffering from septic or other distributive shock, and we have a number of initiatives that we believe will support its continued, increased adoption in 2019," said Dr. George Tidmarsh, La Jolla's president and chief executive officer, in a press release.