6-K

QuickLinks -- Click here to rapidly navigate through this document

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, DC 20549

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER
PURSUANT TO RULE 13a-16 OR 15d-16 OF
THE SECURITIES EXCHANGE ACT OF 1934

June 16, 2008

Commission File Number 001-14956

BIOVAIL CORPORATION
(Translation of Registrant's name into English)

7150 Mississauga Road, Mississauga, Ontario, CANADA, L5N 8M5
(Address of principal executive office and zip code)

Registrant's telephone number, including area code: (905) 286-3000

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.

Form 20-F ý Form 40-F o

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1).

Yes o No ý

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7).

Yes o No ý

Indicate by check mark whether by furnishing the information contained in this form the registrant is also hereby furnishing the information to the Commission pursuant to Rule 12g 3-2(b) under the Securities Exchange Act of 1934.

Yes o No ý

BIOVAIL CORPORATION

This Report of Foreign Private Issuer on Form 6-K is incorporated by reference into the registration statements on Form S-8 (Registration Nos. 333-92229 and 333-138697) of Biovail Corporation.

INDEX

Exhibit 99.1	Letter to Shareholders dated June 16, 2008
Exhibit 99.2	Form of Proxy

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

	Biovail Corporation
Date: June 16, 2008	By:	/s/ Jennifer Tindale Jennifer Tindale Vice President & Associate General Counsel

i

QuickLinks

BIOVAIL CORPORATION
INDEX
SIGNATURES

EX-99.1

QuickLinks -- Click here to rapidly navigate through this document

Exhibit 99.1

June 16, 2008

Dear Fellow Shareholder of Biovail Corporation,

It is now time for you to determine the future direction of Biovail.

Your Company can move forward, guided by an independent, capable and knowledgeable Board of Directors. Or it can be dragged backward by Eugene Melnyk, the former Chairman and CEO who wants to gain control of your Board through his own nominees.

You have received a lot of information to consider as you make this crucial decision. Essentially, however, there are four key questions:

THE BOARD:    As a Biovail shareholder, are you better served by an independent, capable and experienced Board of Directors ... or by Eugene Melnyk's less-experienced and hand-picked nominees?

THE RECORD:    Do you want Biovail to move forward with an enhanced Board and strong new management ... or relive the history of lost value, lost opportunities, litigation and regulatory investigation when Eugene Melnyk was Chairman and CEO of Biovail?

THE STRATEGY:    Is there more potential value for you in Biovail's forward-looking New Strategic Focus, designed for a changing pharmaceutical market ... or in Eugene Melnyk's ill-considered return to an outdated business model?

THE VALUE POTENTIAL:    Are you more likely to benefit from a disciplined Board and management dedicated to stewardship of your investment and returning capital to all shareholders ... or from individuals installed by Eugene Melnyk for his own purposes?

In each case, we believe your interests are best served by supporting the Biovail nominees to the Board. Objective review confirms our recommendation:

RiskMetrics Group (formerly Institutional Shareholder Services or ISS), which is widely recognized as one of the leading independent corporate governance and proxy advisory firms, recommends that Biovail shareholders VOTE FOR BIOVAIL'S SLATE OF NOMINEES. Their analysis and recommendations are relied upon by many major financial institutions, investment firms, mutual funds and fiduciaries throughout North America. We have enclosed a news release describing the RiskMetrics recommendations.

Your Board of Directors unanimously recommends that you:
• Vote FOR Biovail's Nominees to the Board
• Reject the Dissident Melnyk Nominees
Vote only the BLUE proxy: Do NOT use the Yellow Melnyk proxy

THE BOARD

•

Biovail has added to the strength of the existing Board with five new independent and experienced nominees. Together with the returning Directors, these nominees bring decades of combined service on public company boards — and the corporate governance expertise that goes with it — as well as extensive pharmaceutical and financial expertise. The Biovail nominees share a commitment to enhancing value for all 56,000 Biovail shareholders.

•

Eugene Melnyk has nominated individuals who have past or current business and personal relationships with him. Only one currently serves on the board of a Canadian public company. The nominees include Mr. Melnyk's proposed figurehead CEO, Bruce Brydon, who previously had that title, despite working only part-time and submitting his resignation twice, citing lack of operational accountability.

•

Even if he remains "retired", Mr. Melnyk — if successful — could exercise far greater control over Biovail than his investment would warrant through his influence over these nominees. His Board could, for example, reject the Company's recent settlement with the United States Department of Justice, which could expose Biovail to criminal indictments. If found guilty, the Company would be excluded from doing business with any health program sponsored by the U.S. federal government for a minimum of five years. These programs represent a material proportion of Biovail's business.

•

Eugene Melnyk is attempting to take control of your Company without paying you for it.

Your interests are best served by an independent and capable Board representing all shareholders. Vote the BLUE proxy for the Biovail nominees. Reject the Melnyk nominees.

THE RECORD

•

Your Board has moved your Company forward significantly in the short time since Mr. Melnyk stepped down as Chairman and was banned from acting as a Biovail director by his settlement with the Ontario Securities Commission. Your Board has completed the first review of strategic alternatives that was independent of Mr. Melnyk. It has developed and begun to implement a New Strategic Focus that repositions Biovail to be a stronger, and more profitable, competitor in a rapidly evolving industry. Your Board has further strengthened senior management with the appointment of Bill Wells as CEO — a seasoned business leader with years of experience at Biovail and other global companies.

•

Biovail's record under Eugene Melnyk is far less positive. While Mr. Melnyk was CEO, between 2001 and 2004 — the Lost Years — the Company's share price fell by approximately 64%. As a senior executive until late February 2008, he was responsible for the product development pipeline, which suffered under his management, the effects of which are being felt today. The Company became embroiled in civil, criminal and regulatory investigations and proceedings which damaged the Company's reputation and has — so far — cost shareholders more than $175 million in legal fees and settlement expenses and consumed vast amounts of management time.

•

Prior to that, beginning under the nominal leadership of Mr. Brydon in 2000, Mr. Melnyk led Biovail into its disastrous foray into the United States primary care market; a short-sighted commercial strategy that resulted in more than $300 million in write-downs.

Your interests are best served by a Board and management that are already taking steps to correct and move beyond the mistakes of the past. Vote the BLUE proxy for the Biovail nominees. Reject the Melnyk nominees.

2

THE STRATEGY

•

The right strategy under the right management will be fundamental to the return on your investment. That strategy has been developed by your Board working with Biovail's experienced management team and leading external advisors. The New Strategic Focus will reposition the Company for greater profitability in a changing competitive landscape, while leveraging its existing strengths. The other choice is the Melnyk proposal which is based on an antiquated and unsuccessful business model that fails to reflect today's marketplace.

•

Biovail's New Strategic Focus is described at length in the May 9 Management Proxy Circular. In the short-term, it aligns the Company's cost base with its revenues. For example, it includes the closing of the underused and unprofitable Puerto Rico facilities — a step that will reduce expenses and has created no issues with our key commercial partners. The Board's strategy builds on the Company's core capabilities in drug delivery, formulation and manufacturing excellence. It also creates new opportunities for higher margins, a range of commercialization options, longer product exclusivity, and improved prescription reimbursement.

•

Significantly, Biovail intends to focus on developing products to fill the large unmet needs in specific niches of the growing specialty central nervous system (CNS) market. This niche focus presents outstanding opportunities and mitigates risk: the investment in clinical trials is much lower since patient numbers required for these trials are much lower and the measure of success of those trials is clear and well-defined. More information on the New Strategic Focus and the CNS initiative is available at www.biovail.com by clicking on the 2008 Annual Meeting button at the top of Biovail's homepage.

•

The New Strategic Focus holds far greater prospects for value enhancement and far less developmental, regulatory and commercial risk than the notions proposed by Mr. Melnyk.

•

Eugene Melnyk's proposal appears to be based on a failing model that would keep Biovail as a "middleman" pursuing a wide range of undifferentiated, convenience and compliance-based products that compete with intensely competitive generic manufacturers. At its best, this is a low-margin business where few high-quality opportunities exist. At the same time, he proposes to pursue "bio-similars" which is a high-risk, high cost and unproven segment of the industry. It is also a complete departure from Biovail's existing business. Illogically, Mr. Melnyk would pursue a strategy that is simultaneously low-reward and high-risk.

Your interests are best served by a Board and management that are implementing an effective new strategy designed for the direction the market is moving, not by a broken model from the past. Vote the BLUE proxy for the Biovail nominees. Reject the Melnyk nominees.

THE VALUE POTENTIAL

•

Your Board is committed to delivering significant and sustainable value to Biovail shareholders. While no one can predict the market price of your shares, your Board has taken important steps to improve the reputation, performance and the prospects for the Company by correcting the errors and omissions of the Melnyk Lost Years and by setting a promising new direction for Biovail.

•

Your Board believes strongly in the importance of returning capital to shareholders. We are increasing efficiencies and reducing costs to create additional sources of capital. We intend to return excess capital to shareholders.

3

•

Your Board has recently confirmed its intention to maintain Biovail's dividend of $1.50 per share annually, and has launched a successful share repurchase program, under which over 1 million shares have already been purchased.

•

Delivering the potential value in Biovail requires the focused strategy, the disciplined management and the dedicated oversight of an independent Board of Directors.

Your interests are best served by electing a Board that has both the commitment and the capability to build long-term value and return capital to you. Vote the BLUE proxy for the Biovail nominees. Reject the Melnyk nominees.

Time is short. Your vote will make a difference to the outcome of this critical decision.

We recommend that you vote today for an independent, capable and effective Biovail Board that is in a stronger position to deliver sustainable long-term value for all shareholders. We urge you act in your own best interests by rejecting the Melnyk slate and electing the Biovail nominees who can represent you on your Board of Directors.

Yours sincerely,

Dr. Douglas J.P Squires Chairman of the Board	William M. Wells Chief Executive Officer

Note:    An independent leading proxy advisory firm, RiskMetrics Group, recommends that Biovail shareholders vote for Biovail's slate of nominees. Shareholders can read an investor presentation based on what Biovail presented to RiskMetrics at www.biovail.com by clicking on the 2008 Annual Meeting button at the top of Biovail's homepage.

Biovail Shareholders: The Proxy to Vote is Blue

Your vote is important, regardless of how many shares you own. Submit your BLUE proxy today in favour of the election of the slate of director nominees set out in the Management Proxy Circular and BLUE proxy.

Voting is a quick and simple process. To be sure your vote is counted completed BLUE proxies must be received by 10:00 a.m. on June 23, 2008. Due to the limited time available, we recommend voting by internet, telephone or fax today or no later than 24 hours before the deadline.

Shareholders with questions or needing assistance in voting their BLUE proxy are encouraged to call Biovail's Proxy Solicitation Agent, Georgeson at:

North American Toll-Free: 1-866-676-3028
Bank and Broker and collect calls accepted: 1-212-440-9800

Even if you have already voted using the dissident proxy, you have every right to change your vote simply by executing the BLUE form of proxy: It is the later-dated proxy that will be counted.

Please discard any proxy or related materials you may have received from the Dissidents and vote using only the control number on the BLUE form of proxy.

Certain statements contained in this letter constitute forward-looking statements relating to, among other things, the Company's objectives, strategies, intentions, plans, beliefs, estimates and expectations, and can generally be identified by the use of words such as "believe", "anticipate", "expect", "intend", "plan", "will", "may" and other similar expressions. Although Biovail believes that the expectations reflected in such forward-looking statements are reasonable, such statements involve risks and uncertainties, and undue reliance should not be placed on such statements. Certain material factors or assumptions are applied in making forward-looking statements, and actual results may differ materially from those expressed or implied in such statements. Many factors could cause actual results to differ from these expectations, including those described under the heading "Risk Factors" contained in our most recent Annual Report on Form 20-F. Biovail undertakes no obligation to update or revise any forward-looking statement.

4

QuickLinks

Exhibit 99.1

Biovail Shareholders: The Proxy to Vote is Blue

EX-99.2

QuickLinks -- Click here to rapidly navigate through this document

Exhibit 99.2

Instructions for Completion of BLUE Proxy for the Annual Meeting of Biovail Corporation to be held on June 25, 2008

YOU MUST ACT QUICKLY FOR YOUR VOTE TO COUNT — THIS BLUE PROXY MUST BE RECEIVED NO LATER THAN 10:00 A.M. (TORONTO TIME) ON MONDAY, JUNE 23, 2008.

VOTE YOUR BLUE FORM OF PROXY TODAY USING ONE OF THE METHODS AVAILABLE BELOW.

1.

This BLUE form of proxy ("Blue Proxy") is solicited by Management of the Company. Shareholders are directed to reference the accompanying Management Proxy Circular for more detailed information.

2.

You have the right to appoint a proxyholder, who need not be a shareholder, to attend and act on your behalf at the Meeting. If you wish to appoint a person or company other than the persons designated in this Blue Proxy, please insert the name of your chosen proxyholder in the space provided (see reverse).

3.

This Blue Proxy must be signed by you, the registered holder, or by your attorney duly authorized by you in writing, or, in the case of a corporation, by a duly authorized officer or representative of the corporation; and if executed by an attorney, officer or other duly appointed representative, the original or a notarial copy of the instrument so empowering such person, or such other documentation in support as shall be acceptable to the Chairman of the Meeting, must accompany this Blue Proxy. If the Common Shares represented by this Blue Proxy are registered in the name of more than one owner (for example, joint ownership, trustees, executors, etc.), then all those registered owners should sign this Blue Proxy.

4.

This Blue Proxy should be signed in the exact manner as the name appears on the Blue Proxy.

5.

If this Blue Proxy is not dated, it will be deemed to bear the date on which it was mailed to shareholders.

6.

The Common Shares represented by this Blue Proxy will be voted for or withheld from voting in accordance with the instructions of the holder, on any ballot that may be called for and, if the holder has specified a choice with respect to any matter to be acted, the Common Shares will be voted accordingly. This Blue Proxy confers discretionary authority on the proxyholder to vote as they see fit in respect of each matter set forth herein if no choice is specified and in respect of any amendments or other matters that may properly come before the Meeting. If you do not direct your vote in respect of any matter, the proxyholders designated by Management in this Blue Proxy will vote FOR items 1 and 2.

7.

Time is of the essence. This Blue Proxy, to be effective, must be returned and received at the office of CIBC Mellon Trust Company, by one of the methods listed below, no later than 10:00 a.m. (Toronto time) on Monday, June 23, 2008, or in the case of any adjournment or postponement of the Meeting, no later than 48 hours before the time of such reconvened meeting. Failure to properly complete or deposit a Blue Proxy may result in its invalidation.

VOTE USING THE TELEPHONE, INTERNET, MAIL or FAX

To vote by mail or fax:

Complete, sign and date the reverse hereof and return this proxy in the envelope provided, or fax, to:

Mail: In the prepaid envelope provided
Fax: (416) 368-2502

In order to expedite your vote, you may use a touch-tone telephone or the Internet.

To vote by telephone, call toll free 1-866-271-1207. You will be prompted to provide your 13 digit control number printed below your pre-printed name and address. The telephone voting service is available until June 23, 2008 at 10:00 a.m. (Toronto Time) and you may not appoint a person as proxyholder other than the Management nominees named in the accompanying form of proxy when voting by telephone.

To vote via the Internet, go to www.eproxyvoting.com/biovail and follow the instructions on the website prior to June 23, 2008 at 10:00 a.m. (Toronto Time).

If you have any questions or need assistance completing this Blue Proxy please call:
Georgeson
Toll Free: 1-866-676-3028

Third Mailing

Form of Proxy
(Registered Holders)

This BLUE form of proxy ("Blue Proxy") is solicited by and on behalf of Management of Biovail Corporation, and will be used at the Annual Meeting of Shareholders to be held on Wednesday, June 25, 2008 at 10:00 a.m. (Toronto time).

THIS BLUE PROXY MUST BE RECEIVED NO LATER THAN 10:00 A.M. (TORONTO TIME) ON MONDAY, JUNE 23, 2008.
SEE BACK FOR DELIVERY INSTRUCTIONS.

The undersigned holder of Common Shares of Biovail Corporation ("Biovail" or the "Company") hereby appoints MR. WILLIAM M. WELLS, Chief Executive Officer of the Company, or failing him, MS. WENDY A. KELLEY, Senior Vice-President, General Counsel and Corporate Secretary of the Company, or instead of either of the foregoing                                     , as the proxyholder of the undersigned, to attend and act on behalf of the undersigned at the ANNUAL MEETING OF COMMON SHAREHOLDERS OF BIOVAIL TO BE HELD ON THE 25^th DAY OF JUNE, 2008, and at any adjournment thereof (the "Meeting"), with the power of substitution and with all the powers that the undersigned could exercise with respect to the said shares if personally present and with authority to vote at the said proxyholder's discretion except as otherwise specified herein and to vote and act in said proxyholder's discretion with respect to amendments or variations to matters referred to in the accompanying Notice of Annual Meeting and with respect to other matters that may properly come before the Meeting.

Without limiting the general authorization and powers conferred hereby, the undersigned hereby instructs the said proxyholder to vote the common shares represented by this Blue Proxy as indicated below and hereby revokes any proxy previously given.

               Management recommends that shareholders vote FOR each of the items set out in 1 and 2 below:

1.  Election of Directors	FOR	Withhold
To elect the following Biovail slate of Director nominees: Dr. Douglas J.P. Squires, Mr. Serge Gouin, Mr. David H. Laidley, Mr. J. Spencer Lanthier, Mr. Mark Parrish, Dr. Laurence E. Paul, Mr. Robert N. Power, Mr. Lloyd M. Segal, Mr. Michael R. Van Every and Mr. William M. Wells.	o	o
2.  Re-appointment of Independent Auditors	FOR	Withhold
To re-appoint Ernst & Young LLP as auditors to hold office until the close of the next annual meeting of common shareholders and to authorize the Board of Directors of Biovail to fix the remuneration of the auditors.	o	o

Authorized Signature(s) — Sign Here — This section must be completed for your instructions to be executed.

The undersigned authorizes you to act in accordance with my/our instructions set out above. The undersigned hereby revokes any proxy previously given with respect to the Meeting. If no voting instructions are indicated above, this Blue Proxy will be voted in the discretion of the proxyholder, as he or she may deem fit.

Signature of holder(s):

Date:

Telephone Number:

Request for Quarterly Reports

Biovail's quarterly reports to shareholders are available at www.sedar.com, but if you wish to receive quarterly reports and interim financial statements with accompanying MD&A for the 2008 fiscal year by mail, please mark this box. If you do not mark this box and return this form, you will not receive these documents by mail.    o

Annual Report Waiver

Mark this box if, for fiscal 2008, you do not want to receive the Annual Report containing the Annual Financial Statements and accompanying MD&A. If you do not mark this box, the Annual Report will continue to be sent to you.    o

Third Mailing

QuickLinks

Exhibit 99.2

Mail: In the prepaid envelope provided Fax: (416) 368-2502
THIS BLUE PROXY MUST BE RECEIVED NO LATER THAN 10:00 A.M. (TORONTO TIME) ON MONDAY, JUNE 23, 2008. SEE BACK FOR DELIVERY INSTRUCTIONS.