Shares of ViroPharma Inc., of Exton, rose today after an Oppenheimer & Co. analyst upgraded the stock, citing the potential for sales of Cinryze and minimal impact to sales from generic versions of Vancocin.

The stock was up 86 cents, or 9.6 percent, to $9.81 in midday trading. Shares have traded between $3.79 and $14.55 over the last 52 weeks.

Oppenheimer analyst John Newman upgraded the stock to “Outperform” from “Perform” with a $13 price target, saying the company could surprise investors with sales figures for Cinryze, which treats a genetic condition called hereditary angioedema. It had sales of $25.6 million during the second quarter.

ViroPharma considers the drug its growth driver and expects sales between $80 million and $95 million in 2009. Newman now expects Cinryze sales to reach $100 million in 2009.

Meanwhile, the potential impact of generic versions of the company’s gastrointestinal infection treatment Vancocin is already priced into the stock, Newman said.

In August, a Food and Drug Administration panel of experts voted unanimously that generic drug companies should not have to conduct costly human trials before launching generic versions of Vancocin. The drug accounts for the majority of Viropharma’s revenue and is the only FDA-approved therapy for antibiotic-associated gastrointestinal infection.

ViroPharma had argued that generic drug companies seeking approval to market generic versions of Vancocin should be required to conduct testing in patients with actual gastrointestinal infections before producing a copy of the drug for the market.