Valeant Pharmaceuticals, the embattled Quebec-based drug giant, has named an interim CEO as J. Michael Pearson remains in hospital for severe pneumonia.

The drugmaker has appointed Howard B. Schiller to take over, effective immediately.

Schiller served as the company's chief financial officer from December 2011 through June 2015 and is on its board of directors.

Embattled drug maker

The announcement comes as Valeant tries to overcome controversies that have slashed its stock price by more than half since it posted record highs in August.

Questions have mounted over whether Valeant became too big for its own good by embarking on a series of acquisitions in recent years while cutting research and development spending.

It has also faced accusations of drug price gouging and concerns were further raised about its previously undisclosed relationship with Philidor Rx Services, a U.S. mail-order pharmacy — an affiliation Valeant later severed.

Nonetheless, the company launched an internal review last fall to determine whether there was any wrongdoing in its relationship with Philidor. That review is headed by lead independent director Robert Ingram, who will become the interim chairman of Valeant's board of directors following Wednesday's shuffle in the company's top ranks.

In a statement, Ingram said the timing of Pearson's recovery and return remains uncertain.

"We appreciate the expressions of support and concern for Mike's health that we have received from Valeant's investors, employees, business partners and other stakeholders," he said.

"While Mike's illness was sudden and unexpected, our strong management team has stepped in to keep our businesses on track and thriving."

Before he was admitted into hospital last month, Pearson faced calls to resign. But he was defiant, vowing to put the company's troubles behind it.