An ANDA, or Abbreviated New Drug Application, is the formal submission a pharmaceutical company files with the FDA to get approval to manufacture and sell a generic version of a brand-name drug. Unlike a full new drug application, an ANDA does not require the applicant to prove the drug is safe and effective from scratch. Instead, the generic manufacturer must demonstrate that its product is bioequivalent to the brand-name drug already on the market, meaning it delivers the same active ingredient to the body at the same rate and to the same extent.
How ANDAs Differ From New Drug Applications
When a brand-name drug first seeks FDA approval, its manufacturer submits a New Drug Application (NDA) backed by years of clinical trials proving the drug is safe and works as intended. That process costs hundreds of millions of dollars and takes years to complete. An ANDA skips the clinical trials entirely. The legal foundation for this shortcut is the Drug Price Competition and Patent Term Restoration Act of 1984, commonly called the Hatch-Waxman Amendments, which established bioequivalence as a sufficient basis for approving generic copies of already-approved drugs.
The logic is straightforward: if a generic drug contains the same active ingredient, in the same dosage form, at the same strength, and reaches the bloodstream in the same way as the brand-name product, repeating large-scale safety and efficacy trials would be redundant. The brand-name manufacturer already proved the drug works. The generic manufacturer just needs to prove its version behaves identically in the body.
What Bioequivalence Actually Means
Bioequivalence testing is the scientific core of every ANDA. The generic manufacturer conducts a study, typically in healthy volunteers, comparing how its product performs against the brand-name (reference) drug. Two measurements matter most: the peak concentration of the drug in the bloodstream and the total drug exposure over time. For the generic to pass, the 90% confidence interval for both of these measures must fall within 80% to 125% of the brand-name drug’s values.
That range sounds wide, but it’s a statistical confidence interval, not a measure of how different the two drugs can be. In practice, the average difference between approved generics and their brand-name counterparts is much smaller than those outer limits suggest. The FDA applies the same 80% to 125% window to drugs with a narrow therapeutic index (medications where small dosing differences can cause problems), but adds an additional layer of statistical scrutiny for those products.
Patent Certifications and Legal Challenges
Before a generic can reach the market, the ANDA applicant has to address every patent the brand-name company has listed in the FDA’s Orange Book, a public database of approved drugs and their associated patents. The applicant does this through patent certifications, and the most consequential one is called a Paragraph IV certification.
A Paragraph IV certification is a formal declaration that, in the generic applicant’s view, the brand-name patent is either invalid, unenforceable, or would not be infringed by the generic product. Filing one of these is essentially picking a legal fight with the brand-name manufacturer, who then has 45 days to sue for patent infringement. If the brand-name company does sue, FDA approval of the generic is automatically delayed by 30 months (or until the court resolves the case, whichever comes first).
Other certification options are less combative. An applicant can certify that no patent has been filed, that a listed patent has already expired, or that the generic won’t launch until a specific patent expires. But Paragraph IV certifications are the ones that drive most of the legal battles in the generic drug industry.
The 180-Day Exclusivity Incentive
Because challenging a patent through a Paragraph IV certification carries real legal risk and expense, the law provides a reward. The first generic applicant to file a substantially complete ANDA with a Paragraph IV certification is eligible for 180 days of market exclusivity. During that window, no other generic version of the same drug can be approved.
The 180-day clock starts on whichever comes first: the date the first generic applicant begins selling its product commercially, or the date a court rules the patent invalid, unenforceable, or not infringed. This exclusivity period is enormously valuable. Being the only generic on the market for six months, while the brand-name drug is still priced at a premium, can generate significant revenue for the generic manufacturer. It’s the primary financial incentive driving companies to challenge brand-name patents early.
Review Timelines and Fees
The FDA’s current performance goals, set under the third reauthorization of the Generic Drug User Fee Amendments (GDUFA III) covering fiscal years 2023 through 2027, target a 10-month review cycle for 90% of standard ANDA submissions. Priority ANDAs, which cover drugs in shortage or other high-need categories, have an 8-month goal if the applicant provides certain facility information at least 60 days before submitting. If the manufacturing facility listed in the application isn’t ready for inspection at the time of submission, the review timeline extends to 15 months.
These are goals, not guarantees. Many ANDAs go through multiple review cycles. The FDA may issue a “complete response letter” requesting additional data or corrections, and each resubmission restarts its own review clock. It’s common for the total time from initial submission to final approval to stretch well beyond a single review cycle.
Filing an ANDA isn’t cheap, either. The user fee for fiscal year 2026 is $358,247. Generic manufacturers also pay annual program fees and facility fees on top of the application cost. These fees fund the FDA’s generic drug review program.
What an ANDA Does Not Cover
Not every generic drug goes through the ANDA pathway. Complex generics, such as biosimilars (generic versions of biologic drugs made from living cells), follow a separate approval process under a different section of federal law. ANDAs apply specifically to small-molecule drugs, the traditional pills, capsules, creams, and injectables that can be chemically reproduced.
An ANDA also cannot be used to approve a drug that differs from the brand-name product in active ingredient, dosage form, route of administration, or strength, unless the applicant first files a suitability petition and the FDA agrees the change is appropriate. If the differences are too significant, the applicant may need to file a full NDA with its own clinical data, sometimes called a 505(b)(2) application, which is a hybrid between a brand-name and generic submission.