Filed by Mylan Laboratories Inc.
Pursuant to Rule 425 under the Securities Act of 1933
and deemed filed pursuant to Rule 14a-12
under the Securities and Exchange Act of 1934, as amended

Subject Company: King Pharmaceuticals, Inc.
Commission File No.: 0-24425

     This filing relates to a planned acquisition (the “Acquisition”) by Mylan Laboratories Inc. (“Mylan”) of King Pharmaceuticals, Inc. (“King”), pursuant to the terms of an Agreement and Plan of Merger, dated as of July 23, 2004 (the “Merger Agreement”), by and among Mylan, Summit Merger Corporation (a wholly-owned subsidiary of Mylan) and King. The Merger Agreement is on file with the U.S. Securities and Exchange Commission (the “SEC”) as an exhibit to the joint proxy statement/prospectus on Form S-4 filed by Mylan on September 3, 2004, and is incorporated by reference into this filing.

* * *

Mylan Completes Next Step in Proposed Acquisition of King Pharmaceuticals with Filing of Form S-4 Registration Statement

PITTSBURGH, Sept. 7 — Mylan Laboratories Inc. (NYSE: MYL) and King Pharmaceuticals, Inc. (NYSE: KG) announced today that they took two important actions in connection with moving forward Mylan’s pending acquisition of King.

Mylan’s Vice Chairman and Chief Executive Officer Robert J. Coury, stated, “These filings bring us one step closer to the consummation of the pending acquisition and realizing the potential shareholder value that will be created from the combination of Mylan Laboratories and King Pharmaceuticals.”

The first action was Mylan’s filing, on Friday, September 3, 2004, of a Registration Statement on Form S-4 with the Securities and Exchange Commission (SEC). The Registration Statement covers the Mylan shares to be delivered to King shareholders and includes the Mylan and King preliminary joint proxy statement/prospectus relating to the shareholder meetings which will be held by each company to seek and obtain shareholder approval in connection with the pending transaction.

The second action was the filing, on Thursday, September 2, 2004, by each of Mylan and King with the U.S. Department of Justice and the Federal Trade Commission of the notification forms required by the premerger notification provisions of the Hart-Scott-Rodino Antitrust Improvements Act of 1976.

Additional Information About the Merger and Where To Find It:

In connection with the proposed merger, Mylan and King filed with the SEC on September 3, 2004, a joint proxy statement/prospectus on Form S-4 that contains important information about the Merger. These materials are not yet final and will be amended. Investors and security holders of Mylan and King are urged to read the joint proxy statement/prospectus filed, and any other relevant materials filed by Mylan or King because they contain, or will contain, important information about Mylan, King and the Merger. The preliminary materials filed on September 3, 2004, the definitive versions of these materials and other relevant materials (when they become available) and any other documents filed by Mylan or

King with the SEC, may be obtained for free at the SEC’s website at www.sec.gov. Investors and shareholders of Mylan and King may also read and copy any reports, statements and other information filed by Mylan and King with the SEC at the SEC public reference room at 450 Fifth Street, N.W. Room 1200, Washington, D.C. 20549. Please call the SEC at 800-SEC-0330 or visit the SEC’s website for further information on its public reference room. In addition, the documents filed with the SEC by Mylan may be obtained free of charge by directing such request to: Mylan Laboratories Inc., Attention: Investor Relations, 1500 Corporate Drive, Canonsburg, PA 15317, or from Mylan’s website at www.mylan.com. The documents filed with the SEC by King may be obtained free of charge by directing such request to: King Pharmaceuticals Inc., Attn: Corporate Affairs, 501 Fifth Street, Bristol, TN 37620, or from King’s website at www.kingpharm.com. Investors and security holders are urged to read the joint proxy statement/prospectus and the other relevant materials when such other materials become available before making any voting or investment decision with respect to the proposed transaction.

Mylan, King and their respective executive officers and directors may be deemed to be participants in the solicitation of proxies from the stockholders of Mylan and King in favor of the acquisition. Information about the executive officers and directors of Mylan and their ownership of Mylan common stock is set forth in the proxy statement for Mylan’s 2004 Annual Meeting of Shareholders, which was filed with the SEC on June 28, 2004. Information about the executive officers and directors of King and their ownership of King common stock is set forth in the proxy statement for King’s 2003 Annual Meeting of Shareholders, which was filed with the SEC on September 19, 2003. Investors and shareholders may obtain more detailed information regarding the direct and indirect interests of Mylan, King and their respective executive officers and directors in the acquisition by reading the joint proxy statement/prospectus regarding the acquisition, which is included in the Registration Statement on Form S-4 filed by Mylan with the SEC on September 3, 2004.

Forward-Looking Statements:

This press release includes statements that constitute “forward-looking statements”, including with regard to the consummation of the pending acquisition and the creation of shareholder value. These statements are made pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. Because such statements inherently involve risks and uncertainties, actual future results may differ materially from those expressed or implied by such forward-looking statements. Factors that could cause or contribute to such differences include, but are not limited to: factors relating to satisfaction of the conditions to the acquisition, including requisite shareholder and regulatory approvals; challenges and costs relating to integration of the two businesses; the effect of any changes in customer and supplier relationships and customer purchasing patterns; the impact and effects of legal or regulatory proceedings, actions or changes; general market perception of the transaction; the effects of vigorous competition on commercial acceptance of Mylan’s and King’s products and their pricing; the potential costs and product introduction delays that may result from use of legal, regulatory and legislative strategies by Mylan’s or King’s competitors; uncertainties regarding patent, intellectual and other proprietary property protections; exposure to lawsuits and contingencies associated with both Mylan’s and King’s businesses; the ability to attract and retain key personnel; other uncertainties and matters beyond the control of management of both Mylan and King; and the other risks detailed in the periodic filings filed by Mylan and by King with the Securities and Exchange Commission. Neither Mylan nor King undertakes any obligation to update these statements for revisions or changes after the date of this release.

About Mylan Laboratories:

Mylan Laboratories Inc. is a leading pharmaceutical company with four subsidiaries, Mylan Pharmaceuticals Inc., Mylan Technologies Inc., UDL Laboratories, Inc. and Mylan Bertek

2

Pharmaceuticals Inc., that develop, manufacture and market an extensive line of generic and proprietary products.

About King Pharmaceuticals:

King, headquartered in Bristol, Tennessee, is a vertically integrated branded pharmaceutical company. King, an S&P 500 Index company, seeks to capitalize on opportunities in the pharmaceutical industry through the development, including through in-licensing arrangements and acquisitions, of novel branded prescription pharmaceutical products in attractive markets and the strategic acquisition of branded products that can benefit from focused promotion and marketing and product life-cycle management.

* * *

3