<PAGE>

                                                                 EXHIBIT 4.12.1

                                 FIRST AMENDMENT
                       TO WARRANTHOLDERS RIGHTS AGREEMENT


      FIRST AMENDMENT made and entered into as of October 18, 1999, by and among
AMERICAN PSYCH SYSTEMS HOLDINGS, INC., a Delaware corporation (together with its
successors, the "COMPANY"), the persons identified on the signature pages hereto
as the Investors (the "INVESTORS"), and BANC OF AMERICA COMMERCIAL FINANCE
CORPORATION, formerly known as NationsCredit Commercial Corporation ("BANC OF
AMERICA CF").

                               STATEMENT OF FACTS

      A. The parties hereto are parties to the Warrantholders Rights Agreement,
dated December 23, 1998, to provide Banc of America CF with certain rights
described therein; capitalized terms used in this Amendment and not otherwise
defined herein have the meanings given such terms in the Warrantholders Rights
Agreement.

      B. The Company has executed and delivered to Banc of America CF the
Warrant dated the date hereof (the "WARRANT"), pursuant to which Banc of America
CF was given the right to purchase 1,853,848 shares of Non-Voting Common Stock
(as such number may be adjusted in accordance with the terms of the Warrant) of
the Company at the Exercise Price (as defined in the Warrant), which Warrant was
issued, in part, in complete exchange for that certain warrant issued to Banc of
America CF dated December 23, 1998.

      C. The Company, the Investors and Banc of America CF desire to amend the
Warrantholders Rights Agreement to modify certain terms of the Warrantholders
Rights Agreement as set forth in this Amendment, subject to the terms and
conditions of this Amendment.

                               STATEMENT OF TERMS

      1. AMENDMENT TO WARRANTHOLDERS RIGHTS AGREEMENT. Subject to the terms and
conditions of this First Amendment, the Warrantholders Rights Agreement is
hereby modified by deleting the definition of "Warrants" in Article I in its
entirety and the following new definition of "Warrants" is substituted in lieu
thereof:

            "Warrants" means the Warrant or Warrants originally issued to Banc
            of America CF on October 18, 1999 in exchange for the warrants
            originally issued to Banc of America CF on December 23, 1998, as
            such Warrants may be transferred or otherwise assigned, but only to
            the extent not theretofore exercised, redeemed or expired in
            accordance with their respective terms.

      2.    NO OTHER  AMENDMENTS.  Except  for the  amendments  expressly  set
forth  in  Section  1 of  this  First  Amendment,  the  Warrantholders  Rights
Agreement shall remain unchanged and in full force and effect.


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      3. WAIVER OF PREEMPTIVE RIGHTS. By signing this First Amendment, the
Stockholders hereby waive any and all preemptive rights, anti-dilution rights
and similar rights they have or may in the future have with respect to the
issuance of the Warrants to Banc of America CF.

      4.    COUNTERPARTS.  This First  Amendment  may be  executed in multiple
counterparts,  each of which  shall be  deemed  to be an  original  and all of
which when taken together shall constitute one and the same instrument.

      5.    GOVERNING  LAW.  THIS FIRST  AMENDMENT  SHALL BE GOVERNED  BY, AND
CONSTRUED  IN  ACCORDANCE  WITH,  THE  INTERNAL  LAWS OF THE STATE OF  GEORGIA
APPLICABLE TO CONTRACTS MADE AND PERFORMED IN SUCH STATE.

      6.    BINDING  EFFECT.  This First  Amendment  shall be binding upon and
shall  inure  to the  benefit  of the  parties  hereto  and  their  respective
successors and assigns.

                                      -2-

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      IN WITNESS WHEREOF, the parties hereto have caused this First Amendment to
Warrantholders Rights Agreement to be duly executed and delivered as of the day
and year specified at the beginning hereof.


                                    WARRANTHOLDERS:

                                    BANC OF AMERICA COMMERCIAL FINANCE
                                    CORPORATION, FORMERLY KNOWN AS
                                    NATIONSCREDIT COMMERCIAL CORPORATION


                                    By: /s/ Ronald S. Cohn
                                        --------------------------------
                                    Ronald S. Cohn
                                    Duly Authorized Signatory



                                    COMPANY:


                                    AMERICAN PSYCH SYSTEMS HOLDINGS, INC.


                                    By: /s/ Kenneth Kessler
                                        --------------------------------
                                    Kenneth A. Kessler, M.D.
                                    President and Chief Executive Officer


                                    /s/ Kenneth Kessler
                                    -------------------------------------
                                    DR. KENNETH A. KESSLER



                                    /s/ John Heffner
                                    -------------------------------------
                                    JOHN HEFFNER


                                      -3-


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                                    NAZEM & COMPANY IV, L.P.

                                    By:  NAZEM & ASSOCIATES, L.P., its
                                    General Partner

                                    By: /s/ Jeffrey Krauss
                                        --------------------------------
                                      Name:  Jeffrey Krauss
                                            ----------------------------
                                      Title: General Partner
                                             ---------------------------



                                    APPLEWOOD ASSOCIATES, L.P.

                                    By: /s/ Barry Rubenstein
                                        --------------------------------
                                      Name:  Barry Rubenstein
                                            ----------------------------
                                      Title: General Patner
                                             ---------------------------


                                    WOODLAND PARTNERS

                                    By: /s/ Barry Rubenstein
                                        --------------------------------
                                      Name:  Barry Rubenstein
                                            ----------------------------
                                      Title: General Patner
                                             ---------------------------


                                    SENECA VENTURES

                                    By: /s/ Barry Rubenstein
                                        --------------------------------
                                      Name:  Barry Rubenstein
                                            ----------------------------
                                      Title: General Patner
                                             ---------------------------


                                    WOODLAND VENTURE FUND

                                    By: /s/ Barry Rubenstein
                                        --------------------------------
                                      Name:  Barry Rubenstein
                                            ----------------------------
                                      Title: General Patner
                                             ---------------------------



                                      -4-