Valeant CEO Mike Pearson is back from medical leave

Mike Pearson is back as CEO of Valeant following medical leave, according to a statement from the pharmaceutical company Sunday.

Pearson had been ill with pneumonia and other complications, and took medical leave of absence late in December.

Valeant also announced that it was separating the roles of chairman and CEO. Howard Schiller, who had served as interim CEO, will become chairman.

Because of the timing of Pearson's return, Valeant has postponed its earnings call and withdrawn its guidance for fourth-quarter and full-year 2016 results, and said it will provide an update "in the near term".

Ingram said in the statement, "We are delighted that Mike is back as his vision and execution have been central to Valeant's success over the past eight years, but his illness serves as a reminder of the importance of succession planning. Given the size and breadth of our company, succession planning and building out our senior team to provide additional resources and support for Mike are high priorities for the Board."

Valeant shares have been slammed since the company's relationship with specialty pharma Philidor was scrutinized by short-selling firm Citron Research.

"My immediate priority will be to build stronger relationships with important constituents, such as managed care and other channel partners, regulators and government representatives, while improving Valeant's reporting procedures, internal controls and transparency," Pearson said in the statement.

Valeant shares have dropped 59% over the past year.