The four-way fight in the cosmetic drug and device industry moved to the next round Tuesday when Inamed ( IMDC) said a takeover bid by Allergan ( AGN - Get Report) is superior to a previous offer from Medicis Pharmaceutical ( MRX).

However, Inamed said its board was remaining neutral and not making a recommendation to its shareholders about the Allergan bid. Inamed, based in Santa Barbara, Calif., said the board was reserving its endorsement because Allergan has made a "revised" bid that's "materially different" than last month's offer from the Irvine, Calif., maker of Botox and eye-care drugs.

Inamed also said it can't take sides because it's "unable to enter into a definitive merger agreement with Allergan reflecting the terms of the revised offer until such time, if any, as Inamed's merger agreement with Medicis is terminated."

Both Allergan and Inamed said the financial terms of Allergan's offer are identical to the original proposal. The revision concerns a formal letter, detailing legal and due diligence matters, that Allergan sent Inamed. The letter enables Inamed to accept the offer through Dec. 31. Inamed had requested an irrevocable offer letter, and Allergan complied.

"We are making excellent progress in completing the acquisition of Inamed," said David E. I. Pyott, Allergan's chairman and CEO, in a prepared statement.

Two weeks ago, Medicis issued an ultimatum to Inamed -- reject the Allergan offer by today, or Medicis could to exercise its right to seek a $90 million breakup fee. There was no immediate comment from Medicis on Tuesday.

On Nov. 21, Allergan started an exchange offer for Inamed's stock even though Inamed hadn't responded formally to its takeover bid. The tender offer expires Dec. 20. Allergan's offer is worth $84 a share, either all cash or 0.8498 shares for each share of Inamed.

Medicis, Scottsdale, Ariz., made an offer in March for $30 in cash plus 1.4205 shares for each share of Inamed. Due to fluctuating shares prices, the value of the Medicis offer has bounced around. Based on current prices, it's worth $78 a share.

The Medicis bid for Allergan has been delayed by a request from the Federal Trade Commission for more information. The FTC is supposed to issue an opinion on Dec. 14.

Just to make things interesting, Mentor ( MNT) recently made a $2.2 billion unsolicited takeover offer to Medicis, which was immediately rejected. Mentor, based in Santa Barbara, Calif., competes with Inamed in the field of breast implants.

As with any merger agreement, the negotiations between Inamed and Allergan, as well as those between Inamed and Medicis, are filled with a host of conditions. On Tuesday, Allergan said its offer to Inamed was irrevocable as long as certain conditions were met.

For example, Allergan says it needs to conduct additional due diligence on Juvederm, an antiwrinkle product from Inamed that isn't approved for use in the U.S. yet. Allergan says it wants to "confirm that there are no material undisclosed facts" relating to the development and regulatory-approval process in the U.S.

Allergan also wants to make sure that its offer meets the requirement of the previous Inamed-Medicis agreement that allows Inamed to entertain a "superior proposal" without being cited for breaching that agreement.

Allergan says it has talked to the FTC and "is working to develop a satisfactory plan" to divest Inamed's rights to an experimental skin treatment called Reloxin. The drug is similar to Botox, and analysts say it's the key to both Medicis' interest in Inamed and the main regulatory hurdle to Allergan's takeover proposal.

The latest episode had some last-minute drama. Inamed's board actually rejected the Allergan offer because the two sides failed to reach an agreement in time for a Dec. 5 deadline, according to an Inamed filing with the Securities and Exchange Commission. Although the board's vote was unanimous, Inamed told the SEC on Monday that it "continues to be in active negotiations" with Allergan. Today, Allergan sent its updated takeover offer.

Shares of Inamed lost 4 cents to $85.25, and Medicis rose 54 cents to $34.21. Allergan was up $1.39 to $105.17, and Mentor was off 15 cents to $48.12.