The Quebec-based company is acquiring all common shares of the North Carolina firm in a deal valued at $14.5 billion.
The boards of both companies have approved the deal that was announced Sunday.
Salix is considered a leader in the American gastrointestinal market.
Valeant chairman and chief executive J. Michael Pearson says Salix is an ideal fit for his company's portfolio of specialty products.
Valeant is a multinational specialty pharmaceutical company that develops, manufactures and markets a broad range of pharmaceutical products, primarily in the areas of dermatology, eye health, neurology and branded generics.