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Exhibit 10.6

SEVERANCE AND CONSULTING AGREEMENT

        This Severance and Consulting Agreement (the "Agreement") is made and
entered into between DAVID SOUTHWELL ("SOUTHWELL" or "you" or "your") and
SEPRACOR INC. ("SEPRACOR"), collectively referred to herein as the "Parties"
this 14th day of May 2008.

        NOW, THEREFORE, for good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the Parties hereby agree as
follows:

        1.    Term of Employment.    On May 20, 2008, you shall resign from your
position as Chief Financial Officer of SEPRACOR, at which time your employment
with SEPRACOR shall be terminated (the "Separation Date"). Until the Separation
Date, you shall perform the duties consistent with your position and such duties
that are reasonably assigned to you by the President and Chief Executive Officer
of SEPRACOR.

        2.    Consulting Arrangement.    

        (a)   Beginning on the Separation Date and ending on December 31, 2008
(the "Consulting Period"), unless earlier terminated pursuant to Section 2(b)
below, you shall serve, in an independent contractor capacity, as a consultant
("Consultant") to SEPRACOR. In your capacity as a Consultant, you shall
cooperate with SEPRACOR in transitioning your work and will provide such advice
and perform such projects as are reasonably requested of you by the President
and Chief Executive Officer of SEPRACOR, including but not limited to assisting
SEPRACOR with potential financings, business development opportunities and/or
acquisition related activities. Subject to your execution and the effectiveness
of a release in connection with the termination of your employment in
substantially the form attached hereto as Exhibit A, during the Consulting
Period, SEPRACOR shall pay you in regular bi-weekly installments at the rate of
$530,000 per year and you shall be solely responsible for all state and federal
income taxes, unemployment insurance and social security taxes and for
maintaining adequate workers' compensation insurance for yourself, consistent
with his independent contractor status. Subject to your execution of the release
and Section 5 of this Agreement, during the Consulting Period, you shall be
entitled to participate in SEPRACOR'S executive retiree health benefit program
for which you will reimburse SEPRACOR based on the same cost sharing arrangement
that applied immediately prior to the Separation Date. During the Consulting
Period, SEPRACOR shall reimburse you for all reasonable travel, entertainment
and other expenses incurred or paid by you in connection with, or related to,
the performance of your duties, responsibilities or services under this
Agreement, upon your presentation of documentation, expense statements, vouchers
and/or such other supporting information as SEPRACOR may request.

        (b)   The Consulting Period may be terminated by SEPRACOR prior to
December 31, 2008 upon the occurrence of a material breach by SOUTHWELL of his
Consultant obligations or any other provision of this Agreement; provided,
however, that SEPRACOR shall not terminate the Consulting Period unless it first
provides SOUTHWELL with written notice setting forth in reasonable detail the
facts and circumstances allegedly constituting such material breach and
SOUTHWELL fails to cease and desist from, or cure, such alleged material breach
within 15 days of his receipt of such notice.

        3.    Severance.    

        (a)    Severance Pay.    Subject to Section 5, your execution and the
effectiveness of a release, substantially in the form of Exhibit B hereto, and
the Consulting Period not having been terminated pursuant to Section 2(b) , for
a period of 24 months, which period shall begin on the first day following the
date the Consulting Period ends (the "Severance Period"), SEPRACOR shall pay you
in regular bi-weekly installments at the rate of $795,000 per year (the
"Severance

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Amount"). Each bi-weekly payment will be in the amount of 1/26th the Severance
Amount, less appropriate state, federal and other mandatory withholding amounts
and, to the extent applicable, your portion of the insurance payments referred
to in Section 3(b). By way of clarification, the stock options and restricted
stock you hold shall continue to be governed by the applicable stock option or
stock incentive plan under which they were granted or issued (or any successor
plan thereto) and any related stock option or restricted stock agreement.

        (b)    Continued Medical and Dental Benefits during Severance
Period.    Subject to your execution of the release and Section 5 of this
Agreement, during the Severance Period, you shall be entitled to participate in
SEPRACOR'S executive retiree health benefit program for which you will reimburse
SEPRACOR based on the same cost sharing arrangement that applied immediately
prior to the Separation Date.

        (c)    Use of Vehicle.    You are entitled to continue to use the
SEPRACOR vehicle currently in your possession through the end of the Severance
Period. At the end of the automobile lease, you shall have the option of
purchasing such vehicle from the leasing company (the "Lessor") on terms to be
agreed upon by you and the Lessor.

        (d)    Other Compensation and Benefits.    You acknowledge and agree
that SEPRACOR does not owe you, and is not responsible to pay or provide you,
any compensation, employment benefits, or other amounts not specifically
outlined in this Agreement.

        4.    Participation in Executive Retirement Health Benefit Program
following Severance Period.    Following the Severance Period, for such time as
you elect to continue to participate in SEPRACOR'S executive retiree health
benefit program, you will reimburse SEPRACOR at the lesser of (a) the actual
cost to SEPRACOR of your participation and (b) the rate applicable to former
SEPRACOR employees to elect COBRA health coverage.

        5.    Section 409A.    

        (a)    Distributions.    The following rules shall apply with respect to
distribution of the payments and benefits, if any, to be provided to you under
Section 3:

        (i)    It is intended that each installment of the payments and benefits
provided under Section 3 shall be treated as a separate "payment" for purposes
of Section 409A of the U.S. Internal Revenue Code of 1986, as amended, and the
guidance issued thereunder ("Section 409A"). Neither you nor SEPRACOR shall have
the right to accelerate or defer the delivery of any such payments or benefits
except to the extent specifically permitted or required by Section 409A;

        (ii)   If, as of the date of your "separation from service" from
SEPRACOR (as defined below), you are not a "specified employee" (within the
meaning of Section 409A), then each installment of the payments and benefits
shall be made on the dates and terms set forth in Section 3; and

        (iii)  If, as of the date of your "separation from service" from
SEPRACOR, you are a "specified employee" (within the meaning of Section 409A),
then:

        (A)  Each installment of the payments and benefits due under Section 3
that, in accordance with the dates and terms set forth herein, will in all
circumstances, regardless of when the separation from service occurs, be paid
within the Short-Term Deferral Period (as hereinafter defined) shall be treated
as a short-term deferral within the meaning of Treasury Regulation
Section 1.409A-1(b)(4) to the maximum extent permissible under Section 409A. For
purposes of this Agreement, the "Short-Term Deferral Period" means the period
ending on the later of the 15th day of the third month following the end of your
tax year in which the separation from service occurs and the

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15th day of the third month following the end of SEPRACOR'S tax year in which
your separation from service occurs; and

        (B)  Each installment of the payments and benefits due under Section 3
that is not described in Subsection (A) and that would, absent this subsection,
be paid within the six-month period following your "separation from service"
from SEPRACOR shall not be paid until the date that is six months and one day
after such separation from service (or, if earlier, your death), with any such
installments that are required to be delayed being accumulated during the
six-month period and paid in a lump sum on the date that is six months and one
day following your separation from service and any subsequent installments, if
any, being paid in accordance with the dates and terms set forth herein;
provided, however, that the preceding provisions of this sentence shall not
apply to any installment of payments and benefits if and to the maximum extent
that such installment is deemed to be paid under a separation pay plan that does
not provide for a deferral of compensation by reason of the application of
Treasury Regulation Section 1.409A-1(b)(9)(iii) (relating to separation pay upon
an involuntary separation from service). Any installments that qualify for the
exception under Treasury Regulation Section 1.409A-1(b)(9)(iii) must be paid no
later than the last day of your second taxable year following your taxable year
in which the separation from service occurs.

        (b)   SEPRACOR and SOUTHWELL agree and anticipate that the level of bona
fide services performed by SOUTHWELL after the Separation Date shall be
permanently decreased beneath the level set forth in Treasury Regulation
Section 1.409A-1(h) to constitute a "separation from service" of SOUTHWELL from
SEPRACOR. Solely for purposes of this Section 5(b), SEPRACOR shall include all
persons with whom SEPRACOR would be considered a single employer under
Sections 414(b) and 414(c) of the Internal Revenue Code of 1986, as amended.

        (c)   All reimbursements and in-kind benefits provided under the
Agreement shall be made or provided in accordance with the requirements of
Section 409A to the extent that such reimbursements or in-kind benefits are
subject to Section 409A.

        (d)   It is intended that any amounts payable and benefits provided
under this Agreement shall either be exempt from or comply with Section 409A so
as not to subject SOUTHWELL to payment of any interest, penalties or additional
tax imposed under Section 409A. If and to the extent that SOUTHWELL or SEPRACOR
reasonably determines that any amount payable or benefit provided under this
Agreement would fail to satisfy any applicable requirement of Section 409A and
trigger the additional tax and/or penalties or interest imposed by Section 409A,
the parties shall negotiate in good faith and use reasonable efforts to modify
the Agreement to bring it into compliance with Section 409A.

        (e)   Notwithstanding the foregoing, SEPRACOR makes no representation or
warranty and shall have no liability to you or any other person if any
provisions of this Agreement are determined to constitute deferred compensation
subject to Section 409A but do not satisfy an exemption from, or the conditions
of, such section.

        6.    Non-Compete and Non-Solicit.    

        (a)   Until the termination of the Severance Period, you agree not to
directly or indirectly engage in any business or enterprise (whether as an
owner, partner, officer, employee, director, investor, lender, consultant,
independent contractor or otherwise, except as the holder of not more than 5% of
the combined voting power of the outstanding stock of a publicly held company)
that is a Competitive Business. For purposes of this Agreement, "Competitive
Business" shall mean any business that produces, develops, designs, markets or
sells any compounds to treat insomnia, epilepsy, asthma, chronic obstructive
pulmonary disease or allergic rhinitis; and in addition, any monoamine reuptake
inhibitor for the treatment of major depressive disorder or generalized

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anxiety disorder or any GABA receptor antagonist for the treatment of
generalized anxiety disorder or panic disorder.

        (b)   Until the termination of the Severance Period, you agree not to
directly or indirectly, either alone or in association with others (i) recruit
or solicit, any person who was employed by SEPRACOR at any time during the
period of your employment with SEPRACOR and remains employed by SEPRACOR, or
(ii) solicit, divert or take away, or attempt to divert or to take away, the
business or patronage of any of the clients, customers or accounts, or
prospective clients, customers or accounts, of SEPRACOR which were contacted,
solicited or served by you while you were employed by SEPRACOR;

        (c)   If any restriction set forth in this Section 6 is found by any
court of competent jurisdiction to be unenforceable because it extends for too
long a period of time or over too great a range of activities or in too broad a
geographic area, it shall be interpreted to extend only over the maximum period
of time, range of activities or geographic area as to which it may be
enforceable. You acknowledge that the restrictions contained in this Section are
necessary for the protection of the business and goodwill of SEPRACOR and are
considered by you to be reasonable for such purpose. You agree that any breach
of this provision will cause SEPRACOR substantial and irrevocable damage and
therefore, in the event of any such breach, in addition to such other remedies
which may be available, SEPRACOR shall have the right to seek specific
performance and injunctive relief without posting a bond. The geographic scope
of this Section 6 shall extend to anywhere SEPRACOR or any of its subsidiaries
did business or had plans to do business while you were an employee of SEPRACOR.
If you violate the provisions of this Section 6, you shall continue to be held
by the restrictions set forth in this Section 6, until a period equal to the
period of restriction has expired without any violation.

        7.    Relationship with Affiliates.    You shall not intentionally seek
employment or any agency relationship with SEPRACOR or any of its subsidiaries,
parent corporation(s), or any of its related entities, at any time without the
prior written consent of SEPRACOR. By execution of this Agreement, you hereby
agree to relinquish and resign from all offices and directorships you hold
(i) with SEPRACOR and its subsidiaries and/or (ii) with any entities for which
you are serving as an officer or director at SEPRACOR'S request or as its
nominee, if necessary for SEPRACOR to appoint or nominate another person to fill
such position, immediately upon the earlier of (a) the Separation Date or
(b) the date when you receive a written request from the President and Chief
Executive Office of SEPRACOR, or his designee.

        8.    Return of Property.    You represent, promise and agree that
immediately upon the termination of the Consulting Period you will return to
SEPRACOR all keys, files, records (and copies thereof), equipment (including,
but not limited to, computer hardware, software and printers, wireless handheld
devices, cellular phones, pagers, etc.), SEPRACOR identification, and any other
SEPRACOR-owned property, in your possession or control, other than the SEPRACOR
vehicle currently in your possession, which you will return, unless you exercise
the purchase option set forth above in Section 3(c), upon the termination of the
Severance Period. You further represent, promise and agree that you will leave
intact all electronic SEPRACOR documents, including but not limited to, those
that you developed or helped develop during your employment. You further
represent, promise and agree that on or prior to the Separation Date you will
have cancelled all accounts for your benefit, if any, in SEPRACOR'S name,
including but not limited to, credit cards, telephone charge cards, cellular
phone and/or pager accounts and computer accounts. You confirm that you have not
used any such property belonging to SEPRACOR which has been in your possession,
custody and/or control in a manner that may be detrimental or adverse to
SEPRACOR'S business interests.

        9.    Confidential Information.    You shall not at any time disclose to
any person, firm, or corporation any confidential or proprietary information
concerning the business or affairs of SEPRACOR, which you may have acquired in
the course of, or as incident to, your employment or

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otherwise. You hereby expressly reaffirm your obligations under the terms and
conditions of the Non-Disclosure and Invention Agreement, which you executed
during or prior to your employment with SEPRACOR (the "Confidentiality
Agreement"). The restriction in this Agreement or the Confidentiality Agreement
shall not, however, apply to any information which you can demonstrate through
written evidence has become publicly known through no wrongful action by
SOUTHWELL.

        10.    Cooperation.    Following the Separation Date, you agree, subject
to advance notice, to reasonably cooperate with SEPRACOR in defense or
prosecution of any threatened or actual claims or actions which may be brought
by, against or on behalf of SEPRACOR, its predecessors or any of its current or
former partners, agents, employees, directors or affiliates and which relate to
events or occurrences that transpired or are alleged to have transpired during
your employment with SEPRACOR or service as a Consultant. Such cooperation shall
include, without limitation, being reasonably available to meet with SEPRACOR'S
counsel to prepare for discovery or trial or an administrative hearing,
government investigation or alternative dispute resolution procedure and to
testify truthfully as a witness when reasonably requested by SEPRACOR at
reasonable times and for reasonable time periods. You also agree to cooperate
with SEPRACOR in transitioning your work and will be available to SEPRACOR for
this purpose and any other purpose reasonably requested of you by SEPRACOR. In
the event any such cooperation is required following the Consulting Period and
requires more than de minimis time or effort, SEPRACOR agrees to reimburse you
for reasonable travel, food and lodging expenses for any cooperation provided
after the Consulting Period.

        11.    Governing Law.    This Agreement shall be governed by the laws of
the Commonwealth of Massachusetts (without giving effect to its conflicts of
laws principles) and may be amended or modified only in writing executed by the
parties. Should any provision be declared by any court to be invalid, the
validity of the remaining provisions shall not be affected, and the invalid
provision(s) shall be deemed not a part of this Agreement. The language of all
parts of this Agreement shall be construed as a whole, according to its fair
meaning, and not strictly for or against either party.

        12.    Binding Nature of Agreement.    This Agreement shall be binding
upon and inure to the benefit of SOUTHWELL and SEPRACOR their heirs,
administrators, executors, representatives, successors and assigns.

        13.    Sealed Instrument.    The terms of this Agreement are contractual
in nature and not a mere recital, and it shall take effect as a sealed
instrument.

        14.    Entire Agreement.    This Agreement, together with the
Confidentiality Agreement and the Releases, sets forth the entire agreement
between the Parties pertaining to the subject matter hereof and supersedes all
prior and contemporaneous communications, emails, letters, agreements,
representations, understandings or negotiations between SOUTHWELL, SEPRACOR
and/or their agents and attorneys, including without limitation, the letter
agreement between SOUTHWELL and SEPRACOR dated June 10, 1994 and the Executive
Retirement Agreement between SOUTHWELL and SEPRACOR dated February 1, 2002. This
Agreement may be modified only by a written agreement signed by each of the
Parties hereto. No waiver of the Agreement or any provision hereof shall be
binding upon the Party against whom enforcement of such waiver is sought unless
it is made in writing and signed by or on behalf of such Party.

        15.    Legal Counsel.    You represent that you have been advised, and
have had the opportunity to thoroughly discuss all aspects of this Agreement
with legal counsel retained by you, that you have read and understand the
provisions herein, and that you are voluntarily entering into this Agreement.

        16.    Counterparts.    This Agreement may be executed in two
(2) counterparts, each of which shall be deemed an original, and all of which
together shall constitute one (1) and the same instrument.

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SIGNED AND SEALED:    
/s/ David Southwell

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DAVID SOUTHWELL
 
Dated:    May 14, 2008
SEPRACOR INC.
 
 
BY
 
/s/ Adrian Adams

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Dated:    May 19, 2008 ADRIAN ADAMS
PRESIDENT & CEO    

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EXHIBIT A

Form of Release of Claims to be Signed Upon Termination of Employment

        In connection with your separation from Sepracor Inc. (the "Company") on
[            ], 2008, and in order to receive the benefits as set forth in
Section 2 of the Severance and Consulting Agreement (the "Agreement") between
you and the Company dated [            ], 2008, this agreement must become
binding between you and the Company. By signing and returning this agreement,
you will be entering into a binding agreement with the Company and will be
agreeing to the terms and conditions set forth in the numbered paragraphs below,
including the release of claims set forth in paragraph 1. Therefore, you are
advised to consult with an attorney before signing this agreement and you have
been given more than twenty-one (21) days to do so. If you sign this agreement,
you may change your mind and revoke your agreement during the seven (7) day
period after you have signed it. If you do not so revoke, this agreement will
become a binding agreement between you and the Company upon the expiration of
the seven (7) day revocation period.

        The following numbered paragraphs set forth the terms and conditions
which will apply if you timely sign and return this agreement and do not revoke
it within the seven (7) day revocation period:

        1.     Release—In consideration of the payment of the severance
benefits, which you acknowledge you would not otherwise be entitled to receive,
you hereby fully, forever, irrevocably and unconditionally release, remise and
discharge the Company, its officers, directors, stockholders, corporate
affiliates, subsidiaries, parent companies, successors and assigns, agents and
employees (each in their individual and corporate capacities) (hereinafter, the
"Released Parties") from any and all claims, charges, complaints, demands,
actions, causes of action, suits, rights, debts, sums of money, costs, accounts,
reckonings, covenants, contracts, agreements, promises, doings, omissions,
damages, executions, obligations, liabilities, and expenses (including
attorneys' fees and costs), of every kind and nature which you ever had or now
have against the Released Parties, including, but not limited to, those claims
arising out of your employment with and/or separation from the Company,
including, but not limited to, all claims under Title VII of the Civil Rights
Act of 1964, 42 U.S.C. § 2000e et seq., the Age Discrimination in Employment
Act, 29 U.S.C. § 621 et seq., the Americans With Disabilities Act of 1990, 42
U.S.C. § 12101 et seq., the Family and Medical Leave Act, 29 U.S.C. § 2601 et
seq., the Worker Adjustment and Retraining Notification Act ("WARN"), 29 U.S.C.
§ 2101 et seq., Section 806 of the Corporate and Criminal Fraud Accountability
Act of 2002, 18 U.S.C. § 1514(A), the Rehabilitation Act of 1973, 29 U.S.C.
§ 701 et seq., Executive Order 11246, Executive Order 11141, the Fair Credit
Reporting Act, 15 U.S.C. § 1681 et seq., the Employee Retirement Income Security
Act of 1974 ("ERISA"), 29 U.S.C. § 1001 et seq., the Massachusetts Fair
Employment Practices Act., M.G.L. c. 151B, § 1 et seq., the Massachusetts Civil
Rights Act, M.G.L. c. 12, §§ 11H and 11I, the Massachusetts Equal Rights Act,
M.G.L. c. 93, § 102 and M.G.L. c. 214, § 1C, the Massachusetts Labor and
Industries Act, M.G.L. c. 149, § 1 et seq., the Massachusetts Privacy Act,
M.G.L. c. 214, § 1B, and the Massachusetts Maternity Leave Act, M.G.L. c. 149,
§ 105D, all as amended; all common law claims including, but not limited to,
actions in tort, defamation and breach of contract; all claims to any non-vested
ownership interest in the Company, contractual or otherwise, including, but not
limited to, claims to stock or stock options; and any claim or damage arising
out of your employment with or separation from the Company (including a claim
for retaliation) under any common law theory or any federal, state or local
statute or ordinance not expressly referenced above. Notwithstanding the
foregoing, the release set forth in this Section 1 shall not apply to (a) your
rights under the Agreement, (b) any vested equity interest in the Company,
including vested stock options or (c) the rights you have to be indemnified and
defended by the Company pursuant to the terms of the Company's Restated
Certificate of Incorporation, as amended, or other organizing documents, and the
rights that you have under, or with respect to, the Company's Directors and
Officers liability insurance policies with respect to conduct or events
occurring during, or relating to, your employment by, or while serving as an
officer or director of, the Company. Without limiting the generality of the
foregoing, the Company

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shall continue to cover you under its Directors and Officers liability insurance
policies following the Separation Date in substantially the same amount and on
substantially the same terms as the Company covers its other former officers and
directors.

        2.     On-Going Obligations—You acknowledge and reaffirm your obligation
to keep confidential and not to disclose any and all non-public information
concerning the Company which you acquired during the course of your employment
with the Company, including, but not limited to, any non-public information
concerning the Company's business affairs, business prospects and financial
condition, as is stated more fully in the Non-Disclosure and Invention
Agreement, which you executed during or prior to your employment with the
Company (the "Non-Disclosure Agreement"). You further acknowledge and reaffirm
your obligations under the Agreement for the benefit of the Company.

        3.     Business Expenses and Compensation—You acknowledge that you have
been reimbursed by the Company for all business expenses incurred in conjunction
with the performance of your employment and that no other reimbursements are
owed to you. You further acknowledge that you have received payment in full for
all services rendered in conjunction with your employment by the Company and
that no other compensation is owed to you except as provided in the Agreement.

        4.     Non-Disparagement—You understand and agree that, as a condition
for payment to you of the consideration herein described and described in the
Agreement, you shall not make any false, disparaging or derogatory statements to
any media outlet, industry group, financial institution or current or former
employee, consultant, client or customer of the Company regarding the Company or
any of its directors, officers, employees, agents or representatives or about
the Company's business affairs and financial condition; provided, however, that
nothing herein shall prevent you from making truthful disclosures to any
governmental entity or in any litigation or arbitration. The Company agrees not
to make any false, disparaging or derogatory statements about you to any media
outlet, industry group, financial institution, or current or former employee,
consultant, client, or customer; provided, however, that nothing herein shall
prevent the Company from making truthful disclosures to any governmental entity
or in any litigation or arbitration. In the event that any inquiries are
directed to the Company's Human Resources Office regarding you from prospective
employers, the Company will explain its neutral reference policy, confirm only
the fact of your former employment with the Company, starting and ending dates,
and your job title in the last position held.

        5.     Amendment—This agreement shall be binding upon the parties and
may not be modified in any manner, except by an instrument in writing of
concurrent or subsequent date signed by duly authorized representatives of the
parties hereto. This agreement is binding upon and shall inure to the benefit of
the parties and their respective agents, assigns, heirs, executors, successors
and administrators.

        6.     Waiver of Rights—No delay or omission by the Company or you in
exercising any right under this agreement shall operate as a waiver of that or
any other right. A waiver or consent given by the Company or you on any one
occasion shall be effective only in that instance and shall not be construed as
a bar or waiver of any right on any other occasion.

        7.     Validity—Should any provision of this agreement be declared or be
determined by any court of competent jurisdiction to be illegal or invalid, the
validity of the remaining parts, terms or provisions shall not be affected
thereby and said illegal or invalid part, term or provision shall be deemed not
to be a part of this agreement.

        8.     Tax Provision—In connection with the severance benefits provided
to you pursuant to this agreement and the Agreement, the Company shall withhold
and remit to the tax authorities the amounts required under applicable law, and
you shall be responsible for all applicable taxes with respect to such severance
benefits under applicable law. You acknowledge that you are not relying upon

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advice or representation of the Company with respect to the tax treatment of any
of the severance benefits.

        9.     Nature of Agreement—You understand and agree that this agreement,
together with the Agreement, is a severance agreement and does not constitute an
admission of liability or wrongdoing on the part of the Company.

        10.   Acknowledgments—You acknowledge that you have been given at least
twenty-one (21) days to consider this agreement and that the Company advised you
to consult with an attorney of your own choosing prior to signing this
agreement. You understand that you may revoke this agreement for a period of
seven (7) days after you sign this agreement, and the agreement shall not be
effective or enforceable until the expiration of this seven (7) day revocation
period. You understand and agree that by entering into this agreement you are
waiving any and all rights or claims you might have under The Age Discrimination
in Employment Act, as amended by The Older Workers Benefit Protection Act, and
that you have received consideration beyond that to which you were previously
entitled.

        11.   Voluntary Assent—You affirm that, other than as contained in the
Agreement, no other promises or agreements of any kind have been made to or with
you by any person or entity whatsoever to cause you to sign this agreement, and
that you fully understand the meaning and intent of this agreement. You state
and represent that you have had an opportunity to fully discuss and review the
terms of this agreement with an attorney. You further state and represent that
you have carefully read this agreement, understand the contents herein, freely
and voluntarily assent to all of the terms and conditions hereof, and sign your
name of your own free act.

        12.   Applicable Law—This agreement shall be interpreted and construed
by the laws of the Commonwealth of Massachusetts, without regard to conflict of
laws provisions. You hereby irrevocably submit to and acknowledge and recognize
the jurisdiction of the courts of the Commonwealth of Massachusetts, or if
appropriate, a federal court located in Massachusetts (which courts, for
purposes of this agreement, are the only courts of competent jurisdiction), over
any suit, action or other proceeding arising out of, under or in connection with
this agreement or the subject matter hereof.

        13.   Entire Agreement—This agreement, together with the Agreement,
contains and constitutes the entire understanding and agreement between the
parties hereto with respect to your severance benefits and the settlement of
claims against the Company and cancels all previous oral and written
negotiations, agreements, commitments and writings in connection therewith.
Nothing in this paragraph, however, shall modify, cancel or supersede your
obligations set forth in paragraph 2 herein.

    Sepracor Inc.    
By:
 
 
 
     

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Name:
Title:
   

I hereby agree to the terms and conditions set forth above. I have been given at
least twenty-one (21) days to consider this agreement and I have chosen to
execute this on the date below. I intend that this agreement become a binding
agreement between me and the Company if I do not revoke my acceptance in seven
(7) days by notifying                                    in writing.

              Date    

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David Southwell      

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EXHIBIT B

Form of Release of Claims to be Signed Upon Termination of Consulting Period

        In connection with your separation as an independent contractor from
Sepracor Inc. (the "Company") on [            ], and in order to receive the
benefits as set forth in Section 3 of the Severance and Consulting Agreement
(the "Agreement") between you and the Company dated [            ], 2008, this
agreement must become binding between you and the Company. By signing and
returning this agreement, you will be entering into a binding agreement with the
Company and will be agreeing to the terms and conditions set forth in the
numbered paragraphs below, including the release of claims set forth in
paragraph 1. Therefore, you are advised to consult with an attorney before
signing this agreement and you have been given more than twenty-one (21) days to
do so. If you sign this agreement, you may change your mind and revoke your
agreement during the seven (7) day period after you have signed it. If you do
not so revoke, this agreement will become a binding agreement between you and
the Company upon the expiration of the seven (7) day revocation period.

        The following numbered paragraphs set forth the terms and conditions
which will apply if you timely sign and return this agreement and do not revoke
it within the seven (7) day revocation period:

        1.     Release—In consideration of the payment of the severance
benefits, which you acknowledge you would not otherwise be entitled to receive,
you hereby fully, forever, irrevocably and unconditionally release, remise and
discharge the Company, its officers, directors, stockholders, corporate
affiliates, subsidiaries, parent companies, successors and assigns, agents and
employees (each in their individual and corporate capacities) (hereinafter, the
"Released Parties") from any and all claims, charges, complaints, demands,
actions, causes of action, suits, rights, debts, sums of money, costs, accounts,
reckonings, covenants, contracts, agreements, promises, doings, omissions,
damages, executions, obligations, liabilities, and expenses (including
attorneys' fees and costs), of every kind and nature which you ever had or now
have against the Released Parties, including, but not limited to, those claims
arising out of your employment or consulting arrangement with and/or separation
from the Company, including, but not limited to, all claims under Title VII of
the Civil Rights Act of 1964, 42 U.S.C. § 2000e et seq., the Age Discrimination
in Employment Act, 29 U.S.C. § 621 et seq., the Americans With Disabilities Act
of 1990, 42 U.S.C. § 12101 et seq., the Family and Medical Leave Act, 29 U.S.C.
§ 2601 et seq., the Worker Adjustment and Retraining Notification Act ("WARN"),
29 U.S.C. § 2101 et seq., Section 806 of the Corporate and Criminal Fraud
Accountability Act of 2002, 18 U.S.C. § 1514(A), the Rehabilitation Act of 1973,
29 U.S.C. § 701 et seq., Executive Order 11246, Executive Order 11141, the Fair
Credit Reporting Act, 15 U.S.C. § 1681 et seq., the Employee Retirement Income
Security Act of 1974 ("ERISA"), 29 U.S.C. § 1001 et seq., the Massachusetts Fair
Employment Practices Act., M.G.L. c. 151B, § 1 et seq., the Massachusetts Civil
Rights Act, M.G.L. c. 12, §§ 11H and 11I, the Massachusetts Equal Rights Act,
M.G.L. c. 93, § 102 and M.G.L. c. 214, § 1C, the Massachusetts Labor and
Industries Act, M.G.L. c. 149, § 1 et seq., the Massachusetts Privacy Act,
M.G.L. c. 214, § 1B, and the Massachusetts Maternity Leave Act, M.G.L. c. 149,
§ 105D, all as amended; all common law claims including, but not limited to,
actions in tort, defamation and breach of contract; all claims to any non-vested
ownership interest in the Company, contractual or otherwise, including, but not
limited to, claims to stock or stock options; and any claim or damage arising
out of your employment or consulting arrangement with or separation from the
Company (including a claim for retaliation) under any common law theory or any
federal, state or local statute or ordinance not expressly referenced above.
Notwithstanding the foregoing, the release set forth in this Section 1 shall not
apply to (a) your rights under the Agreement, (b) any vested equity interest in
the Company, including vested stock options or (c) the rights you have to be
indemnified and defended by the Company pursuant to the terms of the Company's
Restated Certificate of Incorporation, as amended, or other organizing
documents, and the rights that you have under, or with respect to, the Company's
Directors and Officers liability insurance policies with respect to conduct or
events occurring during, or relating to, your employment by, or while serving as
an officer or director of, the Company, Without limiting the

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generality of the foregoing, the Company shall continue to cover you under its
Directors and Officers liability insurance policies following the Separation
Date in substantially the same amount and on substantially the same terms as the
Company covers its other former officers and directors.

        2.     On-Going Obligations—You acknowledge and reaffirm your obligation
to keep confidential and not to disclose any and all non-public information
concerning the Company which you acquired during the course of your service to
the Company, including, but not limited to, any non-public information
concerning the Company's business affairs, business prospects and financial
condition, as is stated more fully in the Non-Disclosure and Invention
Agreement, which you executed during or prior to your employment with the
Company (the "Non-Disclosure Agreement"). You further acknowledge and reaffirm
your obligations under the Agreement for the benefit of the Company.

        3.     Return of Company Property—You confirm that you have returned to
the Company all keys, files, records (and copies thereof), equipment (including,
but not limited to, computer hardware, software and printers, wireless handheld
devices, cellular phones, pagers, etc.), Company identification, Company
vehicles and any other Company owned property in your possession or control and
have left intact all electronic Company documents, including but not limited to,
those that you developed or helped develop during your employment or while
providing consulting services. You further confirm that you have cancelled all
accounts for your benefit, if any, in the Company's name, including but not
limited to, credit cards, telephone charge cards, cellular phone and/or pager
accounts and computer accounts.

        4.     Business Expenses and Compensation—You acknowledge that you have
been reimbursed by the Company for all business expenses incurred in conjunction
with the performance of your service to the Company and that no other
reimbursements are owed to you. You further acknowledge that you have received
payment in full for all services rendered in conjunction with your employment by
the Company and the consulting services provided to the Company and that no
other compensation is owed to you except as provided in the Agreement.

        5.     Non-Disparagement—You understand and agree that, as a condition
for payment to you of the consideration herein described and described in the
Agreement, you shall not make any false, disparaging or derogatory statements to
any media outlet, industry group, financial institution or current or former
employee, consultant, client or customer of the Company regarding the Company or
any of its directors, officers, employees, agents or representatives or about
the Company's business affairs and financial condition; provided, however, that
nothing herein shall prevent you from making truthful disclosures to any
governmental entity or in any litigation or arbitration. The Company agrees not
to make any false, disparaging or derogatory statements about you to any media
outlet, industry group, financial institution, or current or former employee,
consultant, client, or customer; provided, however, that nothing herein shall
prevent the Company from making truthful disclosures to any governmental entity
or in any litigation or arbitration. In the event that any inquiries are
directed to the Company's Human Resources Office regarding you from prospective
employers, the Company will explain its neutral reference policy, confirm only
the fact of your former employment with the Company, starting and ending dates,
and your job title in the last position held.

        6.     Amendment—This agreement shall be binding upon the parties and
may not be modified in any manner, except by an instrument in writing of
concurrent or subsequent date signed by duly authorized representatives of the
parties hereto. This agreement is binding upon and shall inure to the benefit of
the parties and their respective agents, assigns, heirs, executors, successors
and administrators.

        7.     Waiver of Rights—No delay or omission by the Company or you in
exercising any right under this agreement shall operate as a waiver of that or
any other right. A waiver or consent given by the Company or you on any one
occasion shall be effective only in that instance and shall not be construed as
a bar or waiver of any right on any other occasion.

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        8.     Validity—Should any provision of this agreement be declared or be
determined by any court of competent jurisdiction to be illegal or invalid, the
validity of the remaining parts, terms or provisions shall not be affected
thereby and said illegal or invalid part, term or provision shall be deemed not
to be a part of this agreement.

        9.     Tax Provision—In connection with the severance benefits provided
to you pursuant to this agreement and the Agreement, the Company shall withhold
and remit to the tax authorities the amounts required under applicable law, and
you shall be responsible for all applicable taxes with respect to such severance
benefits under applicable law. You acknowledge that you are not relying upon
advice or representation of the Company with respect to the tax treatment of any
of the severance benefits.

        10.   Nature of Agreement—You understand and agree that this agreement,
together with the Agreement, is a severance agreement and does not constitute an
admission of liability or wrongdoing on the part of the Company.

        11.   Acknowledgments—You acknowledge that you have been given at least
twenty-one (21) days to consider this agreement and that the Company advised you
to consult with an attorney of your own choosing prior to signing this
agreement. You understand that you may revoke this agreement for a period of
seven (7) days after you sign this agreement, and the agreement shall not be
effective or enforceable until the expiration of this seven (7) day revocation
period. You understand and agree that by entering into this agreement you are
waiving any and all rights or claims you might have under The Age Discrimination
in Employment Act, as amended by The Older Workers Benefit Protection Act, and
that you have received consideration beyond that to which you were previously
entitled.

        12.   Voluntary Assent—You affirm that, other than as contained in the
Agreement, no other promises or agreements of any kind have been made to or with
you by any person or entity whatsoever to cause you to sign this agreement, and
that you fully understand the meaning and intent of this agreement. You state
and represent that you have had an opportunity to fully discuss and review the
terms of this agreement with an attorney. You further state and represent that
you have carefully read this agreement, understand the contents herein, freely
and voluntarily assent to all of the terms and conditions hereof, and sign your
name of your own free act.

        13.   Applicable Law—This agreement shall be interpreted and construed
by the laws of the Commonwealth of Massachusetts, without regard to conflict of
laws provisions. You hereby irrevocably submit to and acknowledge and recognize
the jurisdiction of the courts of the Commonwealth of Massachusetts, or if
appropriate, a federal court located in Massachusetts (which courts, for
purposes of this agreement, are the only courts of competent jurisdiction), over
any suit, action or other proceeding arising out of, under or in connection with
this agreement or the subject matter hereof.

        14.   Entire Agreement—This agreement, together with the Agreement,
contains and constitutes the entire understanding and agreement between the
parties hereto with respect to your severance benefits and the settlement of
claims against the Company and cancels all previous oral and written
negotiations, agreements, commitments and writings in connection therewith.
Nothing in this paragraph, however, shall modify, cancel or supersede your
obligations set forth in paragraph 2 herein.

    Sepracor Inc.    
By:
 
 
 
     

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Name:
Title:
   

        I hereby agree to the terms and conditions set forth above. I have been
given at least twenty-one (21) days to consider this agreement and I have chosen
to execute this on the date below. I intend that this agreement become a binding
agreement between me and the Company if I do not revoke my acceptance in seven
(7) days by notifying                                    in writing.

              Date    

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David Southwell      

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QuickLinks

Exhibit 10.6

SEVERANCE AND CONSULTING AGREEMENT
EXHIBIT A Form of Release of Claims to be Signed Upon Termination of Employment
EXHIBIT B Form of Release of Claims to be Signed Upon Termination of Consulting
Period