Canada's Valeant Pharmaceuticals International and activist investor Bill Ackman have made an unsolicited $47 billion bid to buy Botox maker Allergan in a move to create one of the world's five biggest drug companies.

The offer, if successful, would bring together two mid-sized pharmaceutical companies with expertise in skin care and eye care products.

Ackman's Pershing Square Capital Management, Allergan's largest shareholder with a 9.7 % stake, disclosed in a filing that it supports the bid.

Allergan said it will carefully consider the proposal and "pursue the course of action that it believes is in the best interests of the company's stockholders."

Valeant has offered to pay $48.30 a share in cash and 0.83 of its common share for each Allergan share, valuing the company at $152.88 a share, a premium of over 7% to the company's closing price on Monday.

The offer is 31% higher than Allergan's stock price on April 10, the day before Pershing Square's ownership reached 5%.

Valeant has been on a buying spree since 2010 and last year acquired contact lens maker Bausch & Lomb Holdings. CEO Michael Pearson said in January the company wants to become one of the world's top five pharmaceutical companies by market capitalization by the end of 2016, largely through acquisitions.

The Laval, Quebec-based company, whose products include antidepressant drug Wellbutrin and over-the-counter remedy Cold-FX, favors targets where it can aggressively cut costs. Valeant said it expects to realize at least $2.7 billion in annual cost synergies from a combination with Allergan.

Allergan, which also has a lucrative portfolio of ophthalmic drugs to treat conditions such as glaucoma and dry eye, is larger by revenue, reporting $6.3 billion in sales last year. Valeant reported $5.8 billion in revenue last year.