Exhibit 99.1

Questcor Reports Record Second Quarter Net Sales

-751 Paid Acthar Prescriptions for MS, up 147% from Year Ago Period and up 48%

from Q1 2011-

-45 Paid Nephrotic Syndrome Prescriptions, Significant NS Sales Force Expansion

Underway-

-Record Net Sales of $46.0 Million up 62% from Prior Year Period-

-Record GAAP Net Income per Diluted Share $0.21, up 50% from Prior Year Period-

-Non-GAAP Net Income per Diluted Share $0.23-

-Systemic Lupus Erythematosus (SLE) Announced as Next Acthar Vertical Market-

-Acthar Currently Approved for Use to Treat an Exacerbation and as Maintenance

Therapy in SLE-

-Conference Call Today at 4:30 p.m. ET-

ANAHEIM, CA – July 26, 2011 — Questcor Pharmaceuticals, Inc. (NASDAQ: QCOR) today reported record net sales for its second quarter ended June 30, 2011 of $46.0 million, up 62% compared to $28.3 million for the year ago quarter. Net income for the quarter rose 49% from the same period one year ago to $13.9 million, or $0.21 per diluted share.

A 147% year-over-year increase in the number of paid H.P. Acthar^® Gel (Acthar) prescriptions for the treatment of multiple sclerosis (MS) exacerbations led to increased shipments of Acthar vials. Paid Acthar prescriptions for the treatment of nephrotic syndrome (NS) also increased sharply in the quarter. In addition, paid Acthar prescriptions for the treatment of infantile spasms (IS) were at the highest quarterly level since the third quarter of 2008.

“Clearly, Questcor had a terrific quarter,” said Don M. Bailey, President and CEO of Questcor. “Our focus on expanding the use of Acthar in the treatment of MS exacerbations drove our record second quarter financial performance. Importantly, in spite of the rapid expansion in the use of Acthar for MS exacerbations, we believe that the prescriber base can continue to grow. Accordingly, growing MS sales remains our number one priority. Also, following our early success in nephrotic syndrome, we are immediately and substantially expanding our nephrology selling effort.”

“To generate data in support of the expanded nephrology selling effort, we recently initiated a company-sponsored Phase IV trial to study Acthar in the treatment of NS associated with idiopathic membranous nephropathy,” continued Mr. Bailey. “And, today, we are announcing our fourth on-label target market for Acthar, systemic lupus

1

erythematosus. We believe that this market has many of the same characteristics as our other three vertical markets for Acthar—MS, NS and IS.”

“In the second quarter, our Specialty Sales Force of 77 representatives continued to achieve increased acceptance of Acthar among neurologists as a second-line therapy for MS exacerbations, resulting in a significant increase in Acthar prescriptions,” commented Steve Cartt, Executive Vice President and Chief Business Officer. “Furthermore, in March 2011, our separate five-person Nephrology Sales Force began promoting Acthar to nephrologists. Based on the encouraging growth in Acthar prescribing by nephrologists in the second quarter, we are immediately expanding this sales team from 5 to 28 representatives. All sales managers in this expanded Nephrology Sales Force have been hired, and the filling of new sales positions is underway. We expect the entire Nephrology Sales Force to be trained and actively promoting Acthar to nephrologists by the end of the third quarter of 2011.”

“Importantly, the primary focus for the 77 representatives in our Specialty Sales Force will continue to be MS. However, since Acthar is already considered by most child neurologists to be the treatment of choice for IS, we now feel comfortable significantly reducing the number of sales calls to child neurologists. This reduction will make time available for our Specialty Sales Force to also call on some nephrologists. Through the planned sales call activity of our two sales forces, we expect the total number of target nephrologists that we call on to increase from less than 400 currently to over 3,000 by the end of the third quarter,” concluded Mr. Cartt.

Systemic Lupus Erythematosus (SLE)

Questcor announced today that the Company has identified systemic lupus erythematosus (SLE) as the fourth on-label disease state that it believes has strong therapeutic and commercial potential. Questcor’s effort to conduct an in-depth exploration of the use of Acthar to treat SLE is underway. Acthar currently has three FDA-approved, on-label indications associated with SLE:

Lupus is a chronic autoimmune disease, in which the immune system attacks the body’s own cells and tissue. This can result in swollen, painful joints, skin rash, extreme

2

fatigue, unexplained fever, kidney damage, central nervous system effects and other symptoms. Lupus can lead to arthritis, kidney damage, heart and lung inflammation, central nervous system abnormalities, inflammation of the blood vessels and blood disorders. The course of the disease is unpredictable and, not unlike MS, is often referred to as having a relapsing-remitting character, with periods of disease exacerbation alternating with periods of disease remission.

Unfortunately, SLE treatment options are limited. Oral steroids, often used chronically and at high doses, are the most commonly employed therapeutic approach. The Lupus Foundation of America estimates that 1.5 million Americans have lupus, with SLE accounting for approximately 70% of all cases. Questcor is in the process of estimating the subset of this total patient population likely to be appropriate for possible Acthar use.

Importantly, the Company selected SLE as the next target therapeutic and commercial market for Acthar because of the high unmet need for additional treatments in this disease, the serious and difficult-to-treat nature of SLE, the existence of multiple on-label SLE-related Acthar indications, and the relatively large SLE patient population. In addition, there appear to be distinct parallels between the autoimmune disease processes involved with SLE and the emerging understanding of the multiple mechanisms of action associated with Acthar.

Non-GAAP and GAAP Net Income

Non-GAAP net income for the quarter ended June 30, 2011 was $15.2 million, or $0.23 per diluted common share. Non-GAAP net income for the year ago quarter was $9.9 million, or $0.15 per diluted common share.

On a GAAP basis, net income for the second quarter of 2011 was $13.9 million or $0.21 per diluted common share, including non-cash expenses totaling $1.3 million, or $0.02 per diluted share. Net income for the second quarter of 2010 was $9.3 million, or $0.14 per diluted common share.

The Company believes it is important to share these non-GAAP financial measures with shareholders as they may better represent the ongoing economics of the business and reflect how we manage the business. Accordingly, management believes investors’ understanding of the Company’s financial performance is enhanced as a result of our disclosing these non-GAAP financial measures. Non-GAAP net income should not be viewed in isolation, or as a substitute for, or as superior to, reported GAAP net income. The reconciliation between GAAP and Non-GAAP net income is provided with the financial tables included with this release.

3

Prescription Trend Information for MS, IS and NS

During the second quarter of 2011, Questcor shipped 2,430 vials of Acthar, up 45% compared to 1,680 vials in the year ago quarter, and up 21% compared to 2,010 vials in the first quarter of 2011. The Company’s quarterly vial shipments continue to be subject to significant variation due to the size and timing of individual orders from Questcor’s distributor, and the timing of these orders can significantly affect net sales and net income in any particular quarter. For this reason, as well as other factors causing quarter-to-quarter variability in Questcor’s operating results, the Company believes that investors should consider the Company’s results over several quarters when analyzing the Company’s performance.

Because Acthar prescriptions are filled at specialty pharmacies, the Company does not receive complete information regarding either the number of prescriptions or the number of vials by therapeutic area for all of the patients being treated with Acthar. However, Questcor is able to monitor trends in payer mix and areas of therapeutic use for new Acthar prescriptions based on data it receives from its reimbursement support center. Questcor estimates that over 90% of new Acthar prescriptions are processed by this support center, but believes that very few refill prescriptions are processed there.

In an effort to help investors better understand historical trends in sales of Acthar for each of its current three key therapeutic uses, acute exacerbations of MS, NS, and IS, Questcor has grouped new prescriptions processed by its reimbursement center into two groups — “Paid” and “Fully Rebated.” “Paid” prescriptions include those prescriptions for which Questcor retains the full selling price for Acthar, as well as Tricare prescriptions that receive a 24% rebate. “Fully Rebated” prescriptions are those for which Questcor can identify that it has recorded a rebate liability approximately equal to or, for periods prior to the second quarter of 2010, greater than the price charged to its distributor. From time to time during the past two years, the rebate liability for some government insurance programs has shifted between these two categories. Therefore, the prescriptions that fall into the “Paid” and “Fully Rebated” categories have also shifted over time as follows:

“Paid” prescriptions (Rxs) include all prescriptions in the following payer categories:

“Fully Rebated” prescriptions (Rxs) include:

4

The following tables show, for each of the three key Acthar therapeutic uses, the number of new prescriptions shipped grouped into “Paid” and “Fully Rebated”:

Multiple Sclerosis (and related conditions) New Rxs

Nephrotic Syndrome (and related conditions) New Rxs

5

Infantile Spasms (and related conditions) New Rxs

Notes:

(1) Because the March 2010 health care legislation made Medicaid Managed Care Organization (MCO) prescriptions rebate eligible effective March 23, 2010, a rebate liability for the MCO prescriptions estimated to be filled on or after March 23, 2010 has been accrued. The Company does not have the ability to accurately identify every Medicaid Managed Care prescription so it is possible that some prescriptions identified as “Paid” in the tables may subsequently be reclassified as “Fully Rebated.”

(2) “Related Conditions” includes diagnoses that are either alternative descriptions of the medical condition or are closely related to the medical condition which is the focus of the table. For example, a prescription for “demyelinating disease of the central nervous system” would be included as an MS-related condition for purpose of this table. About 5% of the prescriptions in the tables are for related conditions.

(3) A new prescription may or may not represent a new patient or a new therapy for the patient receiving the prescription. Questcor uses business rules to determine whether a prescription should be classified as new for inclusion in this table. From time to time the

6

Company may modify these rules which could cause some changes to the historic numbers in the tables above.

(4) Historical trend information is not necessarily indicative of future results. Additionally, paid prescriptions should not be viewed as predictive of Questcor’s net sales due to a variety of factors, including changes in the number of vials used in connection with each prescription.

Cash and Share Repurchase Program

As of July 15, 2011, Questcor’s cash, cash equivalents and short-term investments totaled $144 million.

The Company did not repurchase any shares during the second quarter. As of June 30, 2011, Questcor had 62.3 million shares of common stock outstanding, with 4.3 million shares remaining under its common stock repurchase program.

Sales Reserves

Questcor’s sales reserves during the quarter ended June 30, 2011, including the Company’s reserves for Medicaid rebates, represented 23.5% of Gross Sales of $60.1 million.

As required by federal regulations, Questcor provides rebates to state Medicaid programs for Acthar dispensed to Medicaid patients covered under Medicaid rebate-eligible insurance plans. Since the Company does not receive rebate claims from the various state Medicaid agencies until well after the close of the quarter in which the underlying sales took place, the Company establishes reserves for expected rebate claims on a quarterly basis. As a result of the adoption of health care reform, for periods after March 23, 2010, the Company has also included in this reserve an estimate for the liability due to states related to prescriptions of Acthar for patients covered under state Medicaid Managed Care Organizations (Medicaid MCO), which prescriptions were not previously rebate eligible.

Conference Call Details

The Company will host a conference call and slide presentation via webcast today, July 26, 2011 at 4:30 p.m. ET/ 1:30 p.m. PT, to discuss second quarter 2011 results. Don Bailey, President and Chief Executive Officer; and other members of the management team will host the call.

To participate in the live call by telephone, please dial 877-941-8609 for domestic participants and 480-629-9818 for international participants. Participants are asked to call the above numbers 5-10 minutes prior to the starting time. A real-time listen-only

7

webcast of the conference call including the presentation slides will be accessible at www.questcor.com, in the “Investor Relations” section under “Events & Presentations.” If listening via telephone, to view the accompanying presentation slides, navigate to the live webcast as noted above and choose the “No Audio – Slides Only” option to view the slides in conjunction with the live conference call. Listeners should go to the website at least 15 minutes prior to the live conference call to install any necessary audio software.

An audio replay of the call will be available for 7 days following the call. This replay can be accessed by dialing 800-406-7325 for domestic callers and 303-590-3030 for international callers, both using passcode 4455547#. An archived webcast will also be available at www.questcor.com.

About Questcor

Questcor Pharmaceuticals, Inc. is a biopharmaceutical company whose primary product helps patients with serious, difficult-to-treat medical conditions. Questcor’s primary product is H.P. Acthar^® Gel (repository corticotropin injection), an injectable drug that is approved by the FDA for the treatment of 19 indications. Of these 19 indications, Questcor currently generates substantially all of its net sales from three indications: the treatment of acute exacerbations of multiple sclerosis in adults, the treatment of nephrotic syndrome, and the treatment of infantile spasms in children under two years of age. With respect to nephrotic syndrome, the FDA has approved Acthar to “induce a diuresis or a remission of proteinuria in the nephrotic syndrome without uremia of the idiopathic type or that due to lupus erythematosus.” Questcor is also exploring the use of Acthar to treat systemic lupus erythematosus, for which Acthar is approved as both a maintenance therapy and to treat exacerbations. Questcor is also exploring the possibility of developing markets for other on-label indications and the possibility of pursuing FDA approval of additional indications not currently on the Acthar label where there is high unmet medical need. For more information, please visit www.questcor.com.

Note: Except for the historical information contained herein, this press release contains forward-looking statements that have been made pursuant to the Private Securities Litigation Reform Act of 1995. These statements relate to future events or our future financial performance. In some cases, you can identify forward-looking statements by terminology such as “believes,” “continue,” “could,” “estimates,” “expects,” “growth,” “may,” “plans,” “potential,” “should,” “substantial” or “will” or the negative of such terms and other comparable terminology. These statements are only predictions. Actual events or results may differ materially. Factors that could cause or contribute to such differences include, but are not limited to, the following:

8

The risk factors and other information contained in these documents should be considered in evaluating Questcor’s prospects and future financial performance.

Questcor undertakes no obligation to publicly release the result of any revisions to these forward-looking statements, which may be made to reflect events or circumstances after the date of this release.

For more information, please visit www.questcor.com or www.acthar.com.

9

CONTACT INFORMATION:

Questcor Pharmaceuticals, Inc.

Don Bailey

714-786-4210

dbailey@Questcor.com

10

Questcor Pharmaceuticals, Inc.

Consolidated Statements of Income

(In thousands, except per share amounts)

11

Net income per share applicable to common shareholders – basic and diluted may not foot due to rounding.

Use of Non-GAAP Financial Measures

Our “non-GAAP adjusted net income” excludes the following items from GAAP net income:

12

Questcor Pharmaceuticals, Inc.

Consolidated Balance Sheets

(In thousands, except share amounts)

13

Questcor Pharmaceuticals, Inc.

Consolidated Statements of Cash Flows

(In thousands)

14