EXHIBIT 4.3 CERTIFICATE OF AMENDMENT OF RESTATED CERTIFICATE OF INCORPORATION OF McKESSON CORPORATION - ------------------------------------------------------------------------------- Pursuant to Sections 222 and 242 of the General Corporation Law of the State of Delaware - ------------------------------------------------------------------------------- McKesson Corporation, a corporation organized and existing under and by virtue of the provisions of the General Corporation Law of the State of Delaware (the "Corporation"), does hereby certify as follows: FIRST: That Article I of the Corporation's Restated Certificate of Incorporation is hereby amended to read in its entirety as set forth below: ARTICLE I The name of the Corporation is McKesson HBOC, Inc. SECOND: That the foregoing amendment was duly adopted in accordance with the provisions of Sections 222 and 242 of the General Corporation Law of the State of Delaware. IN WITNESS WHEREOF, McKesson Corporation has caused this Certificate to be executed in its corporate name this 12th day of January, 1999. McKESSON CORPORATION By /s/ Nancy A. Miller --------------------------------------------- Name: Nancy A. Miller Title: Vice President and Corporate Secretary 2