Allergan ( AGN), the maker of the Botox injection, extended the deadline for its tender offer to Inamed ( IMDC) shareholders after antitrust approval of the companies' merger was delayed.

According to the offer, Allergan will give Inamed shareholders the choice of either $84 in cash or 0.8498 of an Allergan share. Shares of Allergan were trading 82 cents lower at $112.16 Monday. Inamed shares dipped 33 cents to $89.93.

The exchange offer was initially scheduled to expire on Tuesday but will now end Feb. 22. As of last Friday, about 52.4% of Inamed's shares had been tendered.

Last week, as Allergan reported its quarterly earnings , it wouldn't provide specifics on the effect of the Inamed deal, but said it expected the acquisition's impact to be neutral.

In order to facilitate antitrust approval, Allergan and Inamed plan to give up Inamed's license for the wrinkle-fighting drug Reloxin, which is similar to Botox.

"We look forward to reaching a successful outcome in the U.S. antitrust review of the Inamed acquisition. Meanwhile, we are working diligently on a comprehensive integration plan," said David E.I. Pyott, Allergan's chairman and CEO.

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