Drug Shortage Notifications: Interruption vs Permanent Discontinuation

Two events, one statute: what 506C actually requires

Section 506C separates two manufacturing events in the notice a covered manufacturer files. It does not classify every public shortage record: demand increases, shipping delays, and quality problems can also appear on the list. Under Section 506C of the Federal Food, Drug, and Cosmetic Act (FD&C Act, codified at 21 U.S.C. 356c), a manufacturer must notify the Food and Drug Administration (FDA) in writing of either a permanent discontinuance of manufacture or an interruption in manufacturing that is likely to lead to a meaningful disruption in the domestic supply of a covered drug. One path is an interruption the manufacturer expects to recover from. The other is a decision to stop manufacturing. Stopping manufacture is not, by itself, the same act as withdrawing the finished drug from sale.

The 506C reporting duty is operationalized in three regulations. For New Drug Applications (NDAs) and Abbreviated New Drug Applications (ANDAs), the obligation is codified at 21 CFR 314.81(b)(3)(iii). For biological products licensed under Section 351 of the Public Health Service Act, the parallel requirement is codified at 21 CFR 600.82. For marketed prescription drugs that are not the subject of an approved NDA or ANDA, 21 CFR 310.306 requires the manufacturer to make the notifications in 21 CFR 314.81(b)(3)(iii). Under the statute, the mandate covers a drug that is life-supporting, life-sustaining, or intended for use in the prevention or treatment of a debilitating disease or condition, including use in emergency medical care or during surgery, and a drug that is critical to the public health during a public health emergency declared under 42 U.S.C. 247d. Radiopharmaceutical products are excluded, as is any other product the Secretary designates.

For biopharma executives, supply chain leads, contract development and manufacturing organization (CDMO) operators, and hospital procurement directors, the distinction changes the filing. When a facility encounters a sterile filtration bottleneck, a vial fill-finish stoppage, or an active pharmaceutical ingredient (API) shortfall, the clock is the one in section 506C(b) and the implementing regulations: six months before a planned event, or, when that notice was not possible, as soon as practicable and no later than five business days after the event. Months later, downstream market access and procurement teams see public shortage records and have to tell a temporary allocation from a product the manufacturer has stopped making. The classification made in the notice governs what the filing must contain and which later public records are even relevant.

flowchart TD
    A["Manufacturing Event Detected"] --> B{"Event Classification"}
    B -->|"Technical Stoppage / Delay"| C["Interruption in Manufacturing"]
    B -->|"Stop Manufacture"| D["Permanent Discontinuance"]
    C --> E{"Likely Meaningful Disruption?"}
    E -->|"No: Routine or Insignificant"| F["No 506C Notice"]
    E -->|"Yes: Supply At Risk"| G["Section 506C Filing<br/>Include Estimated Duration"]
    D --> H["Section 506C Filing<br/>Discontinuance Notification"]
    G --> I["Shortage List<br/>Reason and Recovery Fields"]
    H --> J["Shortage List<br/>Reason May Be Discontinuation"]
    D --> M{"Withdrawing the Drug from Sale?"}
    M -->|Yes| K["Section 506I Notice<br/>180 Days Before Withdrawal"]
    K --> L["Orange Book Discontinued Section<br/>or Biologics List Update"]

What the notification must contain, by event type

The content of a 506C notification is set out at 21 CFR 314.81(b)(3)(iii)(c) for NDA and ANDA products and at 21 CFR 600.82(c) for biological products. Paragraph (b) of 21 CFR 600.82 is the timing rule, not the content list. Both content paragraphs require the product name and National Drug Code, the applicant's name, whether the notice relates to a permanent discontinuance or an interruption, a description of the reason, and the estimated duration of the interruption. Manufacturers notify through the CDER Direct NextGen Portal. FDA's Drug Shortages page identifies that portal as the channel for reporting discontinuances and interruptions to the Drug Shortage Staff.

Read against 21 U.S.C. 356c(a) and those content paragraphs, the notice has a shared core and one interruption-specific field: the drug or biological product name, including the NDC; the applicant's name; a statement of whether the notice relates to a permanent discontinuance or an interruption; and the reason for that event. Section 356c(a) adds two conditional disclosures: if an API is a reason or risk factor, the source and any alternative sources the manufacturer knows; and whether an associated device used to prepare or administer the drug is a reason or risk factor. The February 2024 draft guidance recommends operational detail around those statutory items, including the API facility and whether an alternative source is already in an approved application. Those recommendations are not binding while the guidance remains draft.

The divergence is the duration field. 21 U.S.C. 356c(a) requires “the expected duration of the interruption,” and 21 CFR 314.81(b)(3)(iii)(c)(5) and 21 CFR 600.82(c)(5) require “the estimated duration of the interruption in manufacturing.” That element is written for an interruption. A permanent discontinuance is a decision to stop manufacture, so it does not carry an interruption-duration estimate for that applicant's own line. The public shortage list can still show an estimated duration of the shortage after a discontinuation, because that list field describes the market shortage, not the exiting firm's restart. Section 506C(g) tells FDA, as appropriate, to prioritize review of an ANDA or of a supplement that could help mitigate a shortage, or to prioritize an inspection. It does not order the firm to keep manufacturing, and it does not itself authorize importation.

In February 2024, FDA's Center for Drug Evaluation and Research (CDER) and Center for Biologics Evaluation and Research (CBER) jointly issued a revised Level 2 draft guidance entitled Notifying FDA of a Discontinuance or Interruption in Manufacturing of Finished Products or Active Pharmaceutical Ingredients Under Section 506C of the FD&C Act (Docket FDA-2020-D-1057). This draft guidance outlines agency recommendations to assist manufacturers in complying with the statute. Because this document is an agency draft guidance, its specific recommendations are legally nonbinding, but they illustrate the detailed technical data FDA expects during an active supply evaluation.

Specifically, the draft guidance recommends that filers report whether an API shortage or supplier disruption is a contributing factor, identify the specific API manufacturing facility, and detail whether alternative qualified API sources exist in approved applications. For drug-device combination products (such as prefilled syringes, autoinjector pens, or on-body delivery systems), the draft guidance recommends disclosing whether supply delays in device constituent parts or subassemblies contributed to the interruption. Furthermore, the guidance stresses that manufacturers should submit a separate, distinct notification for each discontinuance or interruption event, cautioning filers against combining unrelated product lines into rolling omnibus notifications.

The February 2024 draft guidance states that other reports do not substitute for a 506C notification. Submitting a field alert report under 21 CFR 314.81(b)(1) about a bacteriological contamination incident or a significant chemical defect does not satisfy 506C. A marketing-status report does not satisfy it either. A field alert report tells the FDA district office about a quality defect. The 506C notice is the separate supply filing the Drug Shortage Staff uses.

Timing: the six-month rule, the five-business-day backstop, and where each lives

A persistent point of confusion across biopharma legal, regulatory, and commercial teams is the exact interplay between the six-month advance notice standard and the five-business-day deadline. This confusion stems from the structural separation between statutory text and regulatory codification.

The statutory language in Section 506C(b) of the FD&C Act (21 U.S.C. 356c(b)) establishes the primary notification benchmark: the manufacturer must submit notice to FDA “at least 6 months prior to the date of the discontinuance or interruption,” or, if that is not possible because the event could not be reasonably anticipated that far in advance, the notice must be submitted “as soon as practicable.” Notably, the statute itself does not contain a specific calendar day or business day count for the fallback deadline; it relies entirely on the phrase “as soon as practicable.”

The precise, enforceable numeric backstop was established through formal agency rulemaking. In 21 CFR 314.81(b)(3)(iii)(b) and 21 CFR 600.82(b), FDA operationalized “as soon as practicable” by establishing that notification must occur “in no case later than 5 business days after the discontinuance or interruption in manufacturing occurs.” FDA's public enforcement posture, published on its Drug Shortages non-compliance portal, confirms that the agency treats five business days from the onset of the interruption or discontinuance as the absolute outer legal boundary when six-month advance notice cannot be provided.

To apply this timing standard accurately, manufacturers must evaluate whether an event meets the regulatory definition of a “meaningful disruption.” Under 21 U.S.C. 356c(h)(3) and 21 CFR 314.81(b)(3)(iii)(f), a meaningful disruption is a change in production that is reasonably likely to lead to a reduction in the supply of a drug by a manufacturer that is more than negligible and affects the ability of the manufacturer to fill orders or meet expected demand for its product. The definition does not include interruptions due to matters such as routine maintenance or insignificant changes in manufacturing, so long as the manufacturer expects to resume operations in a short period of time. An event inside that exclusion does not trigger a 506C notice.

What the public sees: FDA-mediated proxies for a confidential filing

When a manufacturer files a Section 506C notification through the CDER Direct NextGen Portal, FDA does not publish that notice. Section 356c(d) does not authorize disclosure of trade secrets or confidential commercial information, and 21 CFR 314.81 limits what appears on the public shortage list. Downstream supply chain analysts, health-system procurement directors, and competing manufacturers do not see the underlying submission. They see public proxies on the FDA Drug Shortages database (accessible at accessdata.fda.gov).

FDA mediates this information by transforming confidential manufacturer submissions into standardized public database fields. Understanding how FDA constructs these fields is essential to interpreting whether an entry signals a temporary allocation or a permanent market exit:

• Shortage Status (Currently in Shortage vs. Resolved): The top-level status reflects FDA's market-wide assessment. Under FDA's published shortage criteria, a status of “Resolved” does not require that every manufacturer has resumed full production or that every packaging presentation is stocked. Rather, FDA designates a shortage as Resolved when the Drug Shortage Staff determines that market demand is fully covered by supply from at least one manufacturer, even if secondary market suppliers remain offline or discontinued.

• Shortage Reason (Categorized per FDASIA): FDA assigns the shortage to one of several standardized reason buckets, including “Requirements related to complying with good manufacturing practices,” “Delay in shipping of the drug,” “Demand increase for the drug,” “Discontinuation of the manufacture of the drug,” and “Other.” Crucially, the reason assigned on the public database is determined by FDA based on its discussions with the manufacturer, and it does not always map cleanly to the underlying event.

• Presentation Availability: Individual dosage forms and packaging configurations (differentiated by NDC) are labeled as “Available,” “Limited Availability,” or “Unavailable.” Per FDA's published guidance, an “Available” presentation status reflects the most current information reported by the manufacturer; it is not an independent FDA verification that wholesale channels possess unconstrained inventory.

• Estimated Shortage Duration / Recovery Timeline: This field reflects the manufacturer's forward-looking projection (e.g., “Estimated recovery Q3 2027” or “Next delivery scheduled April 2027”). Because these timelines are manufacturer-provided estimates, they frequently shift across monthly database revisions as line re-qualification or component lead times evolve.

Worked records: same status, opposite events

To demonstrate how public shortage entries conceal opposite underlying operational realities, consider two live database records captured on October 3, 2026, from the FDA Drug Shortages Database. Both drug products carry the identical top-level status of “Currently in Shortage,” and both list their primary commercial presentations as “Unavailable.” Yet one represents a permanent market exit, while the other represents an active manufacturing line delay with a committed recovery timeline.

Record A: Bacitracin Ophthalmic Ointment (Padagis US LLC). First posted to the FDA database on March 3, 2025, and revised on June 1, 2026, Padagis's single-presentation product (NDC 0574-4022-35, 3.5 g tube) is designated as Unavailable. The public reason category assigned by FDA is “Discontinuation of the manufacture of the drug.” Strikingly, the same row still carries a shortage-duration statement: “Shortage is estimated for 24 months.” That figure is the shortage list’s duration field. The detail page does not describe it as Padagis’s restart date, and it does not explain the 24 months as the time other manufacturers would need to qualify new lines. FDA’s top-level status is a market judgment. A single applicant’s discontinuation can remain “Currently in Shortage” until the Drug Shortage Staff decides that supply from at least one manufacturer covers the market. Readers should not treat the 24-month figure as a commitment that Padagis will resume manufacture.

Record B: Pentostatin Injection (Hospira, Inc., a Pfizer Company). First posted to the FDA database on August 27, 2026, Hospira's Nipent 10 mg single-dose vial (NDC 0409-0801-01) is listed as Unavailable. The confidential 506C notice is not on the public page. What the page does show is the interruption pattern: the manufacturer reported manufacturing delays, and FDA assigned the public reason category “Other.” The detail record explicitly provides operational recovery benchmarks: “Next delivery: Q2 2027; Estimated recovery: Q3 2027; Shortage per manufacturer: manufacturing delays.” Those dates are the manufacturer's current estimates. They can be revised, and they are not an FDA finding that batch release has resumed.

Two supporting contrast records read on the same date illustrate additional complexities. In the case of Streptozocin Powder, For Solution (first posted July 12, 2022; Teva revised September 15, 2026; ESTEVE revised September 16, 2026), Teva's Zanosar 100 mg presentation (NDC 0703-4636-01) is Unavailable with estimated recovery TBD and reason “Other.” The ESTEVE row lists Zanosar 1 g/10 mL (NDC 68118-100-01) as Available and points to a Dear Healthcare Professional letter describing temporary importation of non-FDA-approved Zanosar to address the shortage. The ESTEVE reason column was blank on that read. In the case of Isocarboxazid (Marplan 10 mg tablets) (first posted April 16, 2026; Lifsa revised August 6, 2026), Marplan 10 mg, 100-count (NDC 72336-032-01) is “Limited Availability” under reason “Other,” with estimated recovery TBD. The top-level “Currently in Shortage” banner does not tell a supply team whether the public fields show a stated recovery, a discontinuation reason, or an unstated recovery. For a field-by-field sourcing read of status, availability, reason, and presentation columns, see the June 13, 2026 companion, FDA drug shortage list: reading status, reason, and presentation fields. This article stays on the notification decision: what the filing must contain, when it is due, and which later records the interruption-versus-discontinuance classification leaves behind.

The permanence chain: 506I reports and the Orange Book discontinued section

A permanent discontinuance of manufacture under Section 506C triggers a second, legally distinct chain of statutory obligations that culminates in the formal delisting of the product from active marketing registers. While Section 506C addresses the immediate public health threat of a supply disruption, Section 506I of the FD&C Act (codified at 21 U.S.C. 356i) governs prompt reports of marketing status.

Enacted under the FDA Reauthorization Act of 2017 (FDARA) and amended in 2022 to encompass biologics license applications, Section 506I requires application holders to notify FDA in writing at least 180 days prior to withdrawing an approved drug from sale, or, if 180 days advance notice is not feasible, as soon as practicable but no later than the date of withdrawal. Furthermore, 21 CFR 314.81(b)(3)(iv) establishes an independent postmarketing requirement directing applicants to submit a written notification to the FDA Drug Registration and Listing Office within 30 calendar days of withdrawing an approved drug from commercial distribution.

The operational consequence of a 506I report is decisive: FDA utilizes these notifications to move drug products from the active Prescription Drug Product List to the Discontinued Drug Product List in Approved Drug Products with Therapeutic Equivalence Evaluations (commonly known as the Orange Book). For biological products, section 356i(e) identifies products that are not available for sale as discontinued on the list published under 42 U.S.C. 262(k)(9)(A). Section 356i(f) provides that the notices are not made public and are used only to update those lists. A drug FDA determines was withdrawn for reasons of safety or effectiveness is removed from the Orange Book list, rather than left in the discontinued section.

A move to the discontinued section is not itself a finding that the product was withdrawn for safety or effectiveness. When the withdrawn product is a reference listed drug or reference standard, that distinction matters for ANDA sponsors. The related workflow on discontinued RLD and reference standard pathways explains how that determination is made and what it means for a pending ANDA. This article does not restate that developer workflow.

When notification fails: noncompliance letters in practice

Although Section 506C imposes a mandatory statutory duty, the administrative enforcement mechanism established by Congress is narrowly circumscribed. Under Section 506C(f) of the FD&C Act and 21 CFR 314.81(b)(3)(iii)(e), if FDA concludes that an applicant failed to submit a required notification of a permanent discontinuance or manufacturing interruption within the statutory deadlines, the agency executes a structured public disclosure procedure.

1. Issuance of Formal Non-Compliance Letter: FDA's Drug Shortage Staff issues a formal letter to the applicant documenting the failure to notify the agency at least six months in advance or within the five-business-day regulatory backstop.

2. 30-Calendar-Day Response Window: The manufacturer is granted exactly 30 calendar days from the date of the letter to submit a written response setting forth the reasons for non-compliance and providing the required supply information.

3. 45-Calendar-Day Mandatory Public Posting: Within 45 calendar days of issuing the letter, FDA posts the letter and any response, with trade-secret redactions, unless FDA determines that the letter was issued in error or, after reviewing the response, that the firm had a reasonable basis for not notifying. That exception is in 21 U.S.C. 356c(f)(3).

Despite the severe disruptions documented across domestic supply chains over the past decade, FDA has utilized this statutory non-compliance authority with extreme restraint. According to the agency's CY 2025 Drug Shortages Report to Congress, FDA has issued 11 Section 506C non-compliance letters since 2014, and it issued none in calendar years 2024 or 2025. The Drug Shortages Non-Compliance Portal, content current as of January 18, 2024, lists these seven letter-and-response pairs. The index names the product and the firm. It does not, on its face, classify each missed notice as an interruption or a permanent discontinuance:

• Padagis US LLC: Cyclosporine Injection.

• Bristol-Myers Squibb Company: Paclitaxel injection, protein-bound particles (Abraxane).

• Teva Pharmaceuticals USA, Inc.: Zinc Acetate Capsules.

• Pfizer: Vincristine Sulfate Injection.

• Teva Pharmaceuticals USA, Inc.: Etoposide Injection.

• Par Pharmaceutical & Teva Pharmaceuticals: Tretinoin Capsules. The archive posts a separate letter-and-response pair for each firm.

Not the same obligation: amount reporting under 510(j)(3)

In trade reporting and supply chain discussions, Section 506C shortage notifications are frequently conflated with annual drug amount reporting. Although both obligations share the high-level policy objective of enhancing pharmaceutical supply chain visibility, they arise from completely different statutory authorities, target different entity classes, and operate on entirely separate filing schedules.

Annual drug amount reporting was created by Section 3112(e) of the CARES Act, which added Section 510(j)(3) to the FD&C Act (codified at 21 U.S.C. 360(j)(3)). Under this provision, each person who registers with regard to a listed drug, including repackers and relabelers, must report annually the amount of each listed drug manufactured, prepared, propagated, compounded, or processed for commercial distribution. Unlike Section 506C, which is an event-triggered notice required only when an operational disruption occurs, Section 510(j)(3) is a calendar-year report for listed drugs covered by that section, whether or not supply was interrupted.

The scale of non-compliance across these two regimes illustrates their operational divergence. While FDA has issued only 11 Section 506C non-compliance letters since 2014, the agency's enforcement of Section 510(j)(3) has exposed widespread industry non-reporting. On March 31, 2026, FDA published official public lists of companies that failed to submit calendar year 2024 drug amount reports. According to industry legal analysis published by Hyman, Phelps & McNamara (FDA Law Blog, May 2026), FDA publicly identified more than 7,700 non-compliant entities, comprising 1,254 registrants with active drug listings and 6,480 registrants with inactive listings.

A dated workflow for classifying a supply event and its record trail

To assist regulatory affairs directors, plant managers, and hospital procurement teams in navigating this landscape, the following six-step operational workflow synthesizes the statutory, regulatory, and public record requirements as of October 2026.

1. Step 1: Event Classification (Interruption vs. Discontinuance). Immediately upon encountering a manufacturing variance, supply chain halt, or corporate portfolio review, classify the root event. If the firm intends to resume production once technical, regulatory, or raw-material bottlenecks are resolved, designate the event as an Interruption in Manufacturing. If the firm has decided to terminate commercial distribution of the product permanently, designate the event as a Permanent Discontinuance.

2. Step 2: Product Scope and Threshold Evaluation. Verify that the drug is within 506C scope: prescription drug, life-supporting, life-sustaining, or intended for the prevention or treatment of a debilitating condition (including emergency/surgical use). Confirm that the product is not an excluded radiopharmaceutical. If an interruption is at issue, determine whether the disruption meets the 21 CFR 314.81(b)(3)(iii)(f) threshold for a “meaningful disruption”—ruling out routine scheduled maintenance or minor QC holds expected to resolve without order deficits.

3. Step 3: Execute the Notification Clock. If the event was planned six months in advance (such as a scheduled facility decommissioning or strategic portfolio exit), submit notice at least six months prior to the event date. If the disruption was unexpected (e.g., equipment failure, API contamination, or sudden CDMO contract termination), submit notification through the CDER Direct NextGen Portal as soon as practicable, and no later than 5 business days after the discontinuance or interruption occurs.

4. Step 4: Data Assembly and Submission. Populate the submission with the fields in 21 CFR 314.81(b)(3)(iii)(c) or, for a biological product, 21 CFR 600.82(c): product name, NDC, applicant name, whether the event is a permanent discontinuance or an interruption, and the reason. If the event is an interruption, include the estimated duration of the interruption and the projected re-supply date. When an API or an associated device is a reason or risk factor, include the disclosures required by 21 U.S.C. 356c(a). The February 2024 draft guidance adds nonbinding detail on the API facility, known alternatives in an approved application, and device-constituent delays.

5. Step 5: Monitor Public Shortage Database Proxies. Downstream procurement and portfolio teams must cross-examine the resulting FDA Drug Shortages Database entry. Do not rely solely on top-level status. Verify whether the reason category indicates “Discontinuation of the manufacture of the drug” or operational delays (“Other,” “Requirements related to complying with good manufacturing practices”). Treat estimated recovery quarters as dynamic manufacturer estimates subject to revision.

6. Step 6: Execute Marketing Status and Delisting Obligations (If Discontinuing). If the firm is also withdrawing the drug from sale, submit a Section 506I prompt report of marketing status at least 180 days before withdrawal, or by the withdrawal date if 180 days is not practicable. FDA uses that notice to update the Orange Book or the biologics list. File the separate 30-day written notice to the FDA Drug Registration and Listing Office under 21 CFR 314.81(b)(3)(iv).

Sources

• 21 CFR 314.81 - Other postmarketing reports. Title 21 of the Code of Federal Regulations, Chapter I, Subchapter D, Part 314, Subpart F, Section 314.81. Electronic Code of Federal Regulations (eCFR), Office of the Federal Register, current as of October 1, 2026.

• 21 CFR 600.82 - Notification of a permanent discontinuance or an interruption in manufacturing. Title 21 of the Code of Federal Regulations, Chapter I, Subchapter F, Part 600, Subpart B, Section 600.82. Electronic Code of Federal Regulations (eCFR), Office of the Federal Register.

• 21 U.S.C. 356c - Discontinuance or interruption in the production of life-saving drugs. Section 506C of the Federal Food, Drug, and Cosmetic Act. United States Code, Title 21, Chapter 9, Subchapter V, Part A, Section 356c. Cornell Law School Legal Information Institute.

• 21 U.S.C. 356i - Prompt reports of marketing status. Section 506I of the Federal Food, Drug, and Cosmetic Act. United States Code, Title 21, Chapter 9, Subchapter V, Part A, Section 356i. Cornell Law School Legal Information Institute.

• FDA Drug Shortages Guidance and NextGen Portal Overview. U.S. Food and Drug Administration, Center for Drug Evaluation and Research, content current as of July 15, 2026.

• Drug Shortages: Non-Compliance With Notification Requirement. U.S. Food and Drug Administration, Center for Drug Evaluation and Research, archive of formal 506C non-compliance letters and manufacturer responses.

• FDA Drug Shortages Database: Current and Resolved Drug Shortages and Discontinuations Reported to FDA. U.S. Food and Drug Administration, accessdata portal, records captured October 3, 2026.

• FDA Drug Shortages Detail: Bacitracin Ophthalmic Ointment (Padagis US LLC). U.S. Food and Drug Administration, active ingredient shortage detail, revised June 1, 2026.

• FDA Drug Shortages Detail: Pentostatin Injection (Hospira, Inc., a Pfizer Company). U.S. Food and Drug Administration, active ingredient shortage detail, posted August 27, 2026.

• Guidance for Industry (Draft): Notifying FDA of a Discontinuance or Interruption in Manufacturing Under Section 506C of the FD&C Act. U.S. Food and Drug Administration, CDER and CBER, Level 2 draft guidance, February 2024.

• FDA Guidance Document Docket FDA-2020-D-1057 Landing Page. U.S. Food and Drug Administration, search portal for guidance documents.

• CY 2025 Drug Shortages Report to Congress. U.S. Food and Drug Administration, annual report detailing shortages prevention, mitigation actions, and statutory 506C enforcement statistics.

• Companies that Have Not Submitted Drug Amount Reports Under FD&C Act Section 510(j)(3). U.S. Food and Drug Administration, non-filer lists published March 31, 2026.

• Coronavirus Aid, Relief, and Economic Security Act (CARES Act) Drug Shortage Mitigation Efforts. U.S. Food and Drug Administration, program overview current as of July 20, 2026.

• Frequently Asked Questions About Drug Shortages. U.S. Food and Drug Administration, Drug Shortage Staff consumer and industry guidance.

• Drug Amount Reporting: FDA Publicly Identifies Over 7,700 Noncompliant Companies. Hyman, Phelps & McNamara, P.C. (FDA Law Blog), May 1, 2026.

• Nonclinical Testing Terminology Direct Final Rule (91 FR 60004). Office of the Federal Register, National Archives and Records Administration, September 22, 2026.

• 21 CFR 310.306 - Notification of a permanent discontinuance or an interruption in manufacturing of marketed prescription drugs without approved applications. Electronic Code of Federal Regulations, Office of the Federal Register. Applies to marketed prescription drugs that are not the subject of an approved NDA or ANDA and incorporates 21 CFR 314.81(b)(3)(iii).

• FDA Drug Shortages Detail: Isocarboxazid Tablet (Marplan, Lifsa Drugs LLC). U.S. Food and Drug Administration, active ingredient shortage detail, first posted April 16, 2026, revised August 6, 2026. NDC 72336-032-01.

• FDA Drug Shortages Detail: Streptozocin Powder, For Solution (Zanosar). U.S. Food and Drug Administration, active ingredient shortage detail, first posted July 12, 2022. Teva revised September 15, 2026; ESTEVE revised September 16, 2026.