UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 1)

(Name of Issuer)

(Title of Class of Securities)

(CUSIP Number)

(Name, Address and Telephone Number of Person Authorized to

Receive Notices and Communications)

(Date of Event Which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of Rule 13d-1(e), 13d-1(f) or 13d-1(g), check the following box.  ¨

(Continued on the following pages)

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act.

Explanatory Note

This Amendment No. 1 to Schedule 13D (this “Amendment”) amends the initial Statement on Schedule 13D filed on February 14, 2011 by Katelia Capital Investments Ltd., The Katelia Trust (the “Trust”), Butterfield Trust (Switzerland) Limited (the “Trustee”) and Laurent Asscher (“L. Asscher”) (the “Initial Schedule 13D”). Katelia Capital Investments Ltd., the Trust, the Trustee and L. Asscher are collectively referred to hereinafter as the “Reporting Persons.” Except as otherwise set forth herein, this Amendment does not modify any of the information previously reported in the Initial Schedule 13D.

The information set forth in Item 2 of the Initial Schedule 13D is incorporated herein by reference.

The information set forth in Item 3 of the Initial Schedule 13D is incorporated herein by reference.

The information set forth in Item 6 of this Amendment and Item 4 of the Initial Schedule 13D is incorporated herein by reference.

The following information with respect to the ownership of Tekelec’s Common Stock by each of the Reporting Persons is provided as of September 16, 2011. The percentages used in this Amendment are calculated based upon the number of outstanding shares of Common Stock as reported in Tekelec’s Quarterly Report on Form 10-Q filed for the 2011 fiscal second quarter.

(a)    1.   Aggregate number of shares beneficially owned: See Row 11 of cover page for each Reporting Person.

2.   Percentage: See Row 13 of cover page for each Reporting Person.

(b)    1.   Sole power to vote or to direct vote: See Row 7 of cover page for each Reporting Person.

2.   Shared power to vote or to direct vote: See Row 8 of cover page for each Reporting Person.

3.   Sole power to dispose or to direct the disposition: See Row 9 of cover page for each Reporting Person.

4.   Shared power to dispose or to direct disposition: See Row 10 of cover page for each Reporting Person.

(c)     None.

(d)     Not applicable.

(e)     Not applicable.

Effective April 7, 2011, Katelia Capital Investments Ltd. pledged 2,312,912 shares of Tekelec Common Stock to Merrill Lynch International Bank Limited (“Merrill Lynch”) as security for a credit facility provided by Merrill Lynch to Katelia Capital Investments Ltd. and an affiliate.

Not applicable.

SIGNATURES

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.