Exhibit 32.1

CERTIFICATION PURSUANT TO 18 U.S.C. SECTION
1350, AS ADOPTED
PURSUANT TO SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

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|I, Joel F.
 Gemunder, President and Chief Executive Officer of Omnicare, Inc. (the
 Company), do hereby certify in accordance with 18 U.S.C. 1350, as adopted
 pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that:
|                                                                                                                                                                                                                                 
|                                                                                                                                                                                                                                  | 1. | The
 Quarterly Report on Form 10-Q of the Company for the period ended March 31,
 2009 (the Periodic Report) fully complies with the requirements of section
 13(a) or 15(d) of the Securities Exchange Act of 1934 (15 U.S.C. 78m or
 78o(d)); and
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|                                                                                                                                                                                                                                  | 2. | The
 information contained in the Periodic Report fairly presents, in all material
 respects, the financial condition and results of operations of the Company.                                                                                      

Date: April
30, 2009

| |                                       
| | --------------------------------------
| | /s/ Joel F.
 Gemunder                 
| |                                       
| | Joel F.
 Gemunder                     
| | President
 and Chief Executive Officer

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