**Exhibit 10.6**

March 1, 2007

Douglas E. Reedich                                                                

Dear Doug:

This letter sets forth the agreement between you andSepracor concerning the terms of your resignation from Sepracor.

You will remain an employee of Sepracor carrying outyour responsibilities at my direction or as I may delegate until at the latestDecember 31, 2007 or earlier as determined by either you or Sepracor, at whichtime your resignation will be effective.

If you remain an employee in good standing untilDecember 31, 2007, or if your employment is terminated by Sepracor withoutcause prior to December 31, 2007, then (i) at the time Sepracor makes itsregular bonus payments for 2007, you will be paid a pro rata share of your fullbonus eligibility for 2007 (based on the proportion of 2007 during which youwere employed by Sepracor), and  (ii) youwill be paid bi-weekly until the earlier of December 31, 2009, or the secondanniversary of your termination from Sepracor, with each bi-weekly payment inthe amount of 1/26 of your annual salary and bonus eligibility for 2007 for thefirst year, and 1/26 of your annual salary without bonus for the second year.

In addition, in the event that Sepracor establishes anexecutive retiree health benefit program prior to December 31, 2007, you willbe eligible to participate. For such time as you elect to participate in anysuch program, you will reimburse Sepracor at the lesser of (a) the actual costto Sepracor of your participation and (b) the rate applicable to formerSepracor employees who elect COBRA health coverage.  In the event that Sepracor does not establishan executive retiree health benefit program prior to December 31, 2007,Sepracor will reimburse you the cost of your participation in COBRA for suchtime as you participate in COBRA.

You agree that, after the date of termination of youremployment, you will undertake any necessary preparation testimony in Sepracor’songoing ANDA litigations at no charge to Sepracor aside from costs related toindependent legal representation to which you may be entitled (if any) andreasonable travel, lodging and meals as applicable (“out-of-pocket costs”).  You agree to provide up to 8 hours per monthof transition assistance at Sepracor’s reasonable request until December 31,2009, at no charge to Sepracor aside from out-of-pocket costs.  You agree also to execute a Severance andSettlement Agreement and Release in a form provided by Sepracor which shall include,but not be limited to, provisions involving a general release of all claims,confidentiality, non-competition (in a business capacity), cooperation,non-disparagement and return of company property.

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Notwithstanding anything else to the contrary in thisletter agreement, to the extent that any of the payments that may be madehereunder constitute “nonqualified deferred compensation”, within the meaningof Section 409A and you are a “specified employee” upon your separation (asdefined under Section 409A), the timing of any such payment following yourseparation date shall be modified if, absent such modification, such paymentwould otherwise be subject to penalty under Section 409A.  In any event, the Company makes norepresentation or warranty and shall have no liability to you or to any otherperson if any provisions of this agreement are determined to constitute “nonqualifieddeferred compensation” subject to Section 409A but do not satisfy therequirements of that section.

This letter agreement constitutes the entire agreementbetween Sepracor and you and supercedes all prior agreements andunderstandings, whether written or oral, relating to the subject matter of thisletter agreement, other than the Executive Retention Agreement between Sepracorand you dated February 1, 2002.  For theavoidance of doubt, the stock options and restricted stock awards you holdshall continue to be governed by the applicable stock option or stock incentiveplan under which they were granted or issued (or any successor plan thereto)and any related stock option or restricted stock agreement.

Any changes to the termsof this letter agreement will be binding only if made in writing and agreed byboth you and Sepracor.

Please acknowledge thisletter by signing and dating in the space provided below. Return one signedoriginal at your earliest convenience to me. You may keep the other for yourfiles.

Best regards,

/s/ Timothy J. BarberichTimothy J. BarberichChairman and Chief Executive Officer

Accepted and Agreed:
| /s/ Douglas E.  Reedich         |   | 3/1/2007 |   |
|---------------------------------|--------|----------|--------|
| Douglas E.  Reedich, Ph.D, J.D. | Date   |

 

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