<PAGE>

                                                                  Exhibit 10.18

SENT BY FIRST CLASS MAIL, POSTAGE PREPAID
COPY BY FACSIMILE

                             OmniCell Technologies, Inc.
                             Series J Redemption Notice
                                 February 26, 1999

To Sun Healthcare Group, Inc. ("you"):

Pursuant to the Amended and Restated Articles of Incorporation of OmniCell
Technologies, Inc. (the "Company"), you, as the holder of the Series J
Preferred Stock of the Company, have exercised your option to require the
Company to redeem the Series J Preferred in ten equal quarterly installments.
The first Series J Redemption Date is March 8, 1999 (the "First Redemption
Date").

The number of your shares of Series J Preferred Stock to be redeemed by the
Company on the First Redemption Date is 180,200.  The per share Series J
Redemption Price is $14.03274.  The total redemption price for your shares of
Series J Preferred Stock to be redeemed by the Company on the First
Redemption Date is $2,528,699.75 (the "Redemption Payment").

The Company hereby calls upon you to surrender to the Company your
certificates representing your shares of Series J Preferred Stock to be
redeemed. In the event that less than all of the shares represented by such
certificates are redeemed on the First Redemption Date, the Company will
promptly issue a new certificate representing the unredeemed shares.

      INSTRUCTION:   You are to surrender such certificates to the Company's
      counsel, Cooley Godward LLP, at their offices located at Five Palo Alto
      Square, 3000 El Camino Real, Palo Alto, California, 94306-2155 to the
      attention to Jennifer DiNucci, Esq. on or before March 8, 1999.

You have requested, and by signing below, agree and acknowledge, that the
Redemption Payment is to be applied against your mutually agreed upon
outstanding debt to the Company.  Accordingly, on the First Redemption Date,
the Redemption Payment will not be paid directly to you but will be applied
against your outstanding debt to the Company, which will be reduced
accordingly.

             INSTRUCTION:  Please indicate your receipt of this Redemption
      Notice and your agreement and acknowledgment that on the First
      Redemption Date the Company is to apply the Redemption Payment against
      your outstanding debt to the Company (which outstanding debt exceeds
      the Redemption Payment) by signing the enclosed copy of this Redemption
      Notice and, on or before March 5,1999, returning it by facsimile to
      Jennifer DiNucci at 650-857-0663 and the original by first class mail,
      postage prepaid to: Cooley Godward LLP, Five Palo Alto Square, 3000 El
      Camino Real, Palo Alto, California, 94306-2155, Attn: Jennifer DiNucci,
      Esq.

Acknowledged and Agreed:


----------------------------------------
Sun Healthcare Group, Inc.

By: /s/ Bob Woltil
   -------------------------------------
   CFO

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SENT BY FIRST CLASS MAIL, POSTAGE PREPAID
COPY BY FACSIMILE

                             OmniCell Technologies, Inc.
                             Series J Redemption Notice
                                    May 28, 1999

To Sun Healthcare Group, Inc. ("you"):

Pursuant to the Amended and Restated Articles of Incorporation of OmniCell
Technologies, Inc. (the "Company"), you, as the holder of the Series J
Preferred Stock of the Company, have exercised your option to require the
Company to redeem the Series J Preferred in ten equal quarterly installments.
The next Series J Redemption Date is June 8, 1999 (the "Second Redemption
Date").

The number of your shares of Series J Preferred Stock to be redeemed by the
Company on the Second Redemption Date is 180,200. The per share Series J
Redemption Price is $14.03274. The total redemption price for your shares of
Series J Preferred Stock to be redeemed by the Company on the Second
Redemption Date is $2,528,699.75 plus $540,509.54 in accrued interest (the
"Redemption Payment").

You have already surrendered to the Company your certificates representing
your shares of Series J Preferred Stock to be redeemed. You have requested,
and by signing below, agree and acknowledge, that the Redemption Payment is
to be applied against your outstanding debt to the Company to the extent that
the outstanding debt exceeds the Redemption Payment, and paid in cash to you
to the extent that the Redemption Payment is determined to exceed the
outstanding debt. Accordingly, on the Second Redemption Date, the Redemption
Payment may be paid directly to you in part and applied against your
outstanding debt to the Company in part, which will be reduced accordingly.

             INSTRUCTION: Please indicate your receipt of this Redemption
      Notice and your agreement and acknowledgment that on the Second
      Redemption Date the Company is to apply the Redemption Payment as
      described above by signing the enclosed copy of this Redemption Notice
      and, on or before June 4, 1999, returning it by facsimile to Jennifer
      DiNucci at 650-857-0663 and the original by first class mail, postage
      prepaid to: Cooley Godward LLP, Five Palo Alto Square, 3000 El Camino
      Real, Palo Alto, California, 94306-2155, Attn: Jennifer DiNucci, Esq.

Acknowledged and Agreed:


-------------------------------------
Sun Healthcare Group, Inc.

By: /s/ Bob Woltil
   ----------------------------------
    CFO

<PAGE>

                           OmniCell Technologies, Inc.
                           Series J Redemption Notice
                                  March 3, 2000

To Sun Healthcare Group, Inc. ("you"):

Pursuant to the Amended and Restated Articles of Incorporation of OmniCell
Technologies, Inc. (the "Company"), you, as the holder of the Series J Preferred
Stock of the Company, have exercised your option to require the Company to
redeem the Series J Preferred in ten equal quarterly installments. The next
Series J Redemption Date is March 8, 2000 (the "Fifth Redemption Date").

The number of your shares of Series J Preferred Stock to be redeemed by the
Company on the Fifth Redemption Date is 180,200. The per share Series J
Redemption Price is $14.03274. The total redemption price for your shares of
Series J Preferred Stock to be redeemed by the Company on the Fifth Redemption
Date is $2,528,699.75 (the "Redemption Payment").

The Company hereby calls upon you to surrender to the Company your certificates
representing your shares of Series J Preferred Stock to be redeemed. In the
event that less than all of the shares represented by such certificates are
redeemed on the Fifth Redemption Date, the Company will promptly issue a new
certificate representing the unredeemed shares.

         INSTRUCTION: You are to surrender such certificates to the Company's
         counsel, Cooley Godward LLP, at their offices located at Five Palo Alto
         Square, 3000 El Camino Real, Palo Alto, California, 94306-2155 to the
         attention Sally Kay, Esq. on or before March 8, 2000.

You have requested, and by signing below, agree and acknowledge, that a portion
of the Redemption Payment, $553,383.90*, is to be applied against your mutually
agreed upon outstanding debt to the Company. Accordingly, on the Fifth
Redemption Date, a portion of the Redemption Payment will be applied against
your outstanding debt to the Company which will be reduced accordingly; the
balance of $1,975,315.85* will be paid directly to you.

         INSTRUCTION: Please indicate your receipt of this Redemption Notice and
         your agreement and acknowledgment that on the Fifth Redemption Date the
         Company is to apply a portion of the Redemption Payment against your
         outstanding debt and pay the net balance directly to you by signing the
         enclosed copy of this Redemption Notice and, on or before March 6,
         2000, returning it by facsimile to Sally Kay at 849-7400 and the
         original by first class mail, postage prepaid to: Cooley Godward LLP,
         Five Palo Alto Square, 3000 El Camino Real, Palo Alto, California,
         94306-2155, Attn Sally A. Kay, Esq.

Acknowledged and Agreed:

/s/ Robert A. Wohil
Sun Healthcare Group, Inc.
By: Robert A. Wohil

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* Sun agrees to these amounts subject to further reconciliation; to the extent
the Company owes Sun additional amounts because the setoff amount is actually
less than $553,383.90, the Company will promptly pay such additional amount to
Sun.