(Bloomberg) -- Zoetis Inc. tumbled on Friday after a news report detailed safety concerns associated with the use of the pharmaceutical company’s arthritis drugs for animals.

Shares of the drugmaker fell 7.8%, the biggest drop since November 2022. Zoetis was among the worst performers in the S&P 500 Index on Friday. 

The Wall Street Journal reported earlier that “thousands of reports of side effects” from the use of Zoetis’ drugs Librela and Solensia have spurred reviews from health regulators in the US and Europe. Neither Zoetis nor researchers have linked the drugs and the reported side effects, the paper said.

The medicines are safe and effective, and have low rates of adverse events, the Parsippany, New Jersey-based company said in an emailed statement.

Bank of America Corp. analyst Michael Ryskin said the safety concerns around the drugs have been much discussed in the investment community in the last few months. 

“We don’t see anything materially incremental in this report,” Ryskin, who maintains a buy rating on the firm, wrote in a note to clients.

Friday’s drop adds to the troubles of animal health company’s stock. The firm faces an antitrust probe in the European Union related to its dog pain-relief treatment, and in February, it gave guidance for adjusted earnings per share for 2024 that trailed Wall Street’s expectations. 

Shares have slumped 24% so far this year, erasing about $22 billion in market capitalization.

(Updates with closing prices throughout.)

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