"We wish him a speedy recovery and look forward to him returning to work when he is feeling better," the spokeswoman, Laurie Little, said in a statement.

She declined to provide further details on Pearson's condition, citing privacy concerns, but told Reuters via email that the company plans to "provide further details on his condition as appropriate."

Little did not respond when asked if the disease was life-threatening.

Pearson, 56, joined Valeant as CEO in September 2010 after a 23-year career at McKinsey & Company and became chairman of the board in 2010.

His illness comes as investors are turning up pressure on the Canadian drugmaker to provide a more detailed plan on how it will grow profits in 2016. Under Pearson's leadership, the company has come under U.S. government scrutiny for acquiring off-patent drugs and drastically hiking the prices.

It also has close ties with Philidor RX Services, a pharmacy that has been criticized for aggressive billing practices. Valeant has cut ties with the company, and it is closing down.

Valeant's shares have fallen 55 percent since August, though they have rebounded off more than 2-year lows in the past month to close on Thursday at C$157.68 ($114.10) per share.

Valeant has said it plans to rebuild lost business in 2016 through a new distribution agreement with Walgreen's pharmacies. Still, Valeant's price hikes are the subject of investigations by the U.S. Congress and federal prosecutors in New York and Massachusetts.

Pearson's hospitalization was first reported by The New York Times.