Shares of Omnicare (OCR) fell nearly 8% after the health-care services company said its chief executive, John Figueroa, abruptly quit on Monday.

The Covington, Ky.-based provider of long-term and specialty-care services said its chief financial officer, John Workman, will serve as interim CEO, effective immediately, as the board searches for a permanent replacement. He will simultaneously act as CFO. 

Omnicare did not provide a reason for Figueroa’s resignation, but said he led a “key period of change and revitalization” for the company.

“We wish him and his family the very best for the future,” Omnicare Chairman James Shelton said in a statement.

Workman, who served as CFO for the last two and a half years, is a “proven executive” who has the ability to step in and lead Omnicare through this transition period, Shelton said.  

Workman has been “intimately involved in the improved operations at the company” and is “ideally suited to oversee the continued execution of our strategic plan while ensuring a seamless transition,” Shelton said.

The board’s executive committee will search for a permanent CEO through both internal and external candidates, including Workman.

Also on Monday, Omnicare appointed Nitin Sahney, currently president of its specialty care division, to chief operating officer, effective immediately. The new role includes responsibility for the long-term-care division.

Omnicare said its fiscal 2012 guidance remains unchanged. It currently anticipates full-year revenues of $6.1 billion to $6.2 billion and earnings in the range of $3.10 to $3.20 a share, excluding one-time items.

Analysts in a Thomson Reuters poll are currently looking for per-share earnings of $3.18 on slightly higher sales of $6.25 billion.

Follow Jennifer Booton on Twitter at @Jbooton