Exhibit 4.3

MYLAN INC.,

as Issuer,

SOMERSET PHARMACEUTICALS, INC.,

as Guaranteeing Subsidiary,

The GUARANTORS from time to time parties hereto

and

THE BANK OF NEW YORK MELLON,

as Trustee

FIRST SUPPLEMENTAL INDENTURE

DATED as of NOVEMBER 29, 2011

TO THE INDENTURE

DATED as of SEPTEMBER 15, 2008,

3.75% CASH CONVERTIBLE NOTES DUE 2015

FIRST SUPPLEMENTAL INDENTURE (this “Supplemental Indenture”), dated as of November 29, 2011, among Mylan Inc., a Pennsylvania corporation (the “Company”), Somerset Pharmaceuticals, Inc. (the “Guaranteeing Subsidiary”), a Delaware corporation and a Subsidiary of the Company, the other Guarantors (as defined in the Indenture referred to herein) and The Bank of New York Mellon, as trustee under the Indenture referred to herein (the “Trustee”).

W I T N E S S E T H

WHEREAS, the Company has heretofore executed and delivered to the Trustee an indenture (the “Indenture”), dated as of September 15, 2008, providing for the issuance of 3.75% Cash Convertible Notes Due 2015 (the “Notes”);

WHEREAS, the Indenture provides that under the circumstances specified therein that the Guaranteeing Subsidiary shall fully and unconditionally guarantee the Company’s obligations under the Notes and the Indenture in accordance with the provisions set forth in Article 11 of the Indenture; and

WHEREAS, pursuant to the provisions of Section 10.01 of the Indenture, the parties hereto are authorized to execute and deliver this Supplemental Indenture.

NOW, THEREFORE, in consideration of the foregoing and for other good and valuable consideration, the receipt of which is hereby acknowledged, the Guaranteeing Subsidiary, the Company and the other Guarantors and the Trustee mutually covenant and agree for the equal and ratable benefit of the Holders of the Notes as follows:

1. CAPITALIZED TERMS. Capitalized terms used herein without definition shall have the meanings assigned to them in the Indenture.

2. AGREEMENT TO GUARANTEE. The Guaranteeing Subsidiary hereby provides a Guarantee in respect of the Securities on the terms and subject to the conditions set forth in the Guarantee and in the Indenture including but not limited to Article 11 thereof.

3. NO RECOURSE AGAINST OTHERS. No past, present or future director, officer, employee, incorporator, stockholder or agent of the Guaranteeing Subsidiary, as such, shall have any liability for any obligations of the Company or any Guaranteeing Subsidiary under the Notes, any Guarantees, the Indenture or this Supplemental Indenture or for any claim based on, in respect of, or by reason of, such obligations or their creation. Each Holder of the Notes or any Guarantee by accepting a Note waives and releases all such liability. The waiver and release are part of the consideration for issuance of the Notes and this Guarantee.

4. NEW YORK LAW TO GOVERN. THIS SUPPLEMENTAL INDENTURE AND THE WITHIN GUARANTEE SHALL BE GOVERNED BY, AND CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK.

5. COUNTERPARTS. The parties may sign any number of copies of this Supplemental Indenture. Each signed copy shall be an original, but all of them together represent the same agreement.

6. EFFECT OF HEADINGS. The Section headings herein are for convenience only and shall not affect the construction hereof.

7. THE TRUSTEE. The Trustee makes no representations as to, and shall not be responsible in any manner whatsoever for or in respect of the validity or sufficiency of, this Supplemental Indenture or for or in respect of the recitals contained herein, or the within Guarantee all of which recitals are made solely by the Guaranteeing Subsidiary and the Company.

2

IN WITNESS WHEREOF, the parties hereto have caused this First Supplemental Indenture to be duly executed, all as of the date first above written.

Dated: November 29, 2011,

Signature Page to September 2008 Supplemental Indenture

Signature Page to September 2008 Supplemental Indenture

Signature Page to September 2008 Supplemental Indenture

Signature Page to September 2008 Supplemental Indenture