Therapeutic Equivalence Code Checker
Find a Drug's Therapeutic Equivalence Code
Search for a brand-name drug to check if its generic equivalents are therapeutically equivalent and can be substituted without doctor approval.
How This Works
When you see an AB code, it means the generic drug has been tested and proven equivalent to the brand-name drug. This allows pharmacists to substitute it automatically. Other codes like BC or BD indicate that substitution may not be safe without doctor approval.
When you pick up a prescription at the pharmacy, you might not think twice about whether you’re getting the brand-name drug or a cheaper generic version. But behind that decision is a complex, carefully managed system designed to ensure safety, effectiveness, and cost savings. At the heart of this system is the Orange Book - the official FDA publication that tells pharmacists and doctors which generics can be safely swapped for brand-name drugs. It’s not just a list. It’s the rulebook that keeps millions of Americans getting the right medicine at the right price.
What Exactly Is the Orange Book?
The Orange Book is the Approved Drug Products with Therapeutic Equivalence Evaluations, published monthly by the U.S. Food and Drug Administration (FDA). First released in 1980, it was created under the Hatch-Waxman Act of 1984 to balance two goals: encouraging innovation in new drugs while making affordable generic versions available. The name comes from its original orange cover - now just a nickname, but one everyone in healthcare knows.
The Orange Book doesn’t list every drug on the market. It only includes drugs approved by the FDA based on both safety and effectiveness. That means drugs approved only for safety (like some older pre-1938 medications) or still under review (like those in the DESI program) aren’t included. It also doesn’t cover biologics - those are tracked separately, though biosimilars are starting to get their own pathway.
Today, the Orange Book contains evaluations for over 15,000 approved drug products. Each entry links a brand-name drug to its generic equivalents - and tells you whether those generics are considered interchangeable.
Therapeutic Equivalence: What It Really Means
Therapeutic equivalence isn’t just about having the same active ingredient. It’s a three-part test:
- Pharmaceutical equivalence: The generic must contain the same active ingredient, in the same amount, in the same form (tablet, capsule, injection, etc.) as the brand-name drug.
- Bioequivalence: The generic must be absorbed into the body at the same rate and to the same extent as the brand. This is tested through clinical studies measuring blood levels over time.
- FDA approval: The generic must be manufactured under strict quality controls (Current Good Manufacturing Practices) and labeled correctly.
If a drug passes all three tests, the FDA assigns it a Therapeutic Equivalence (TE) code. These codes are short - usually two letters - but they carry a lot of weight.
Here’s how they work:
- A codes mean the drug is therapeutically equivalent to the brand-name version. These are the ones pharmacists can substitute without asking the doctor.
- B codes mean it’s not considered equivalent. Substituting these could affect how the drug works in your body.
But it gets more specific. The second letter in the code tells you why:
- AB - Proven bioequivalent, no issues. This is the gold standard. You can swap it freely.
- AN - Nasal spray or inhaler with proven equivalence. These are complex, but still approved for substitution.
- AO - Oral solution with proven equivalence.
- AX - Not equivalent due to insufficient data. Don’t substitute.
- BC - Potential bioequivalence issues. Substitution may require doctor approval.
- BD - Bioequivalence not established. Avoid substitution.
These codes aren’t just for pharmacists. Insurance companies, pharmacy benefit managers, and state laws all use them to decide what gets covered and what can be swapped automatically.
Why TE Codes Matter in Real Life
Imagine you’re prescribed a blood thinner like warfarin. It’s a narrow therapeutic index drug - meaning even small differences in how much enters your bloodstream can lead to dangerous bleeding or clots. The FDA is extra cautious here. Only drugs with solid AB ratings get approved for substitution.
But not all drugs are this straightforward. Inhalers, topical creams, and injectables are harder to test. A generic inhaler might use a different propellant or nozzle design. Does that change how the drug gets into your lungs? The FDA says no - if the clinical effect and safety profile match the brand, it gets an A code. But proving that takes more data, and it’s why some complex generics take longer to get approved.
Real-world problems happen when people misunderstand these codes. In 2022, Walgreens reported over $1.2 million in rejected insurance claims because pharmacists misread TE codes for products coded BC or BD. These aren’t interchangeable - but if a pharmacist assumes they are, the claim gets denied, and the patient ends up paying full price or going without.
On the flip side, CVS Health built an automated system in 2021 that checks TE codes in real time during prescription processing. The result? A 63% drop in substitution errors and $47 million saved annually in avoided claim rejections.
Who Uses the Orange Book - and How Often?
It’s not just pharmacists. Here’s who relies on it daily:
- Pharmacists: 92% say the Orange Book is essential for their job. But 67% admit it’s hard to interpret without training.
- Doctors: Many don’t know the TE code system well. They write prescriptions for brand names, not realizing the generic may be just as safe - or may not be.
- Insurance companies: They use TE codes to build formularies. If a drug has an A code, they’ll usually cover the generic first.
- State boards of pharmacy: Every state requires TE code verification before allowing automatic substitution. Some states even require patient consent for certain drugs.
The FDA estimates pharmacists spend an average of 12.7 minutes per complex prescription checking the Orange Book. That’s time that could be spent counseling patients - which is why professional groups like the National Community Pharmacists Association offer certification courses. Over 8,400 pharmacists took one in 2022.
And yet, only 41% of community pharmacists feel very confident interpreting TE codes without a reference guide. That’s a gap - and it’s why mistakes happen.
The Bigger Picture: Cost Savings and Market Impact
The Orange Book isn’t just about safety - it’s about saving money. Thanks to the Hatch-Waxman Act and the system it created, generics now make up 90.7% of all prescriptions filled in the U.S. But they cost only 22.8% of what brand-name drugs do.
Between 2010 and 2019, generic drugs saved the U.S. healthcare system $1.67 trillion. In 2022 alone, the FDA approved 758 new generic drugs - a 14.3% jump from the year before.
That’s not just good for patients. It’s good for the whole system. Insurance premiums stay lower. Out-of-pocket costs shrink. Hospitals and clinics can stretch their budgets further.
But it’s not perfect. Critics point to inconsistencies in TE coding for complex products. Inhalers, transdermal patches, and compounded drugs still pose challenges. The FDA responded in 2022 with updated guidance to clarify how to evaluate these, making the system more transparent.
What’s Changing in 2025?
The FDA is modernizing the Orange Book. The old print version is gone - now it’s fully digital. The new online version, rolling out fully in 2024, lets you search by drug name, active ingredient, applicant name, or TE code - all in one place.
Future updates will include more detail on device components for combination products (like auto-injectors with generics), clearer labeling of bioequivalence data sources, and better filtering for narrow therapeutic index drugs.
One thing won’t change: the core principle. If a generic doesn’t deliver the same clinical effect and safety as the brand, it doesn’t get an A code. No exceptions.
What You Need to Know as a Patient
You don’t need to memorize TE codes. But you should know this:
- If your doctor writes a brand-name drug, ask if a generic with an AB code is available. It’s almost always cheaper and just as safe.
- If your pharmacy switches your medication without telling you, check the label. Look for the generic name and compare it to your previous prescription.
- If you’re on a drug with a narrow therapeutic index - like warfarin, lithium, or levothyroxine - talk to your doctor before switching generics. Even small changes can matter.
- Don’t assume all generics are the same. If you notice a change in how you feel after switching, tell your pharmacist or doctor. It could be a formulation difference, even if the TE code says it’s equivalent.
The Orange Book exists to protect you - not to confuse you. It’s the reason you can fill a 30-day supply of a cholesterol drug for $4 instead of $300. But it only works if everyone understands it.
Where to Find the Orange Book
The FDA makes the Orange Book free and publicly available online. You can search it at accessdata.fda.gov/scripts/cder/ob/. The site is updated monthly, so it’s always current.
There’s also a mobile app version for pharmacists, and many pharmacy management systems integrate the data directly into their workflow.
For patients, the best resource is your pharmacist. Ask them to check the TE code if you’re unsure about a switch. They’re trained to do it - and they’re there to help.
What does an AB code mean in the Orange Book?
An AB code means the generic drug is therapeutically equivalent to the brand-name drug. It has the same active ingredient, dosage form, strength, and route of administration, and has been proven bioequivalent through testing. Pharmacists can substitute it without needing approval from the prescribing doctor.
Can I always switch to a generic drug?
You can switch to a generic only if it has an A code (like AB, AN, or AO) in the Orange Book. If the code is B (like BC or BD), substitution is not recommended. Also, some doctors write "Dispense As Written" or "Do Not Substitute" on prescriptions - that overrides automatic substitution, even if the generic has an A code.
Are all generic drugs the same quality as brand-name drugs?
Yes - if they’re approved by the FDA and carry an A code. The FDA requires generics to meet the same strict standards for purity, strength, quality, and manufacturing as brand-name drugs. The only differences are in inactive ingredients (like fillers or dyes), which don’t affect how the drug works in your body.
Why do some generic drugs cost more than others?
Price differences between generics come from market competition, manufacturing costs, and supply chain issues - not quality. If multiple companies make the same generic, prices usually drop. If only one company makes it, the price stays higher. The Orange Book doesn’t list prices - it only confirms therapeutic equivalence.
Does the Orange Book cover biologics and biosimilars?
No. The Orange Book only covers small-molecule drugs approved under the New Drug Application (NDA) or Abbreviated New Drug Application (ANDA) pathways. Biosimilars - which are complex biological products - are listed in a separate FDA publication called the Purple Book. They follow a different approval process and aren’t assigned TE codes.
What to Do If You’re Confused
If you’re unsure whether a generic is safe to take, don’t guess. Ask your pharmacist to check the Orange Book. They have access to the database and can confirm the TE code. If you’re switching from a brand to a generic and feel different - dizziness, nausea, or changes in how your condition is controlled - tell your doctor immediately. It could be a formulation issue, even if the TE code says it’s equivalent.
The Orange Book is a powerful tool. It’s the reason you can afford your medications. But it only works when people understand it - and use it correctly. Whether you’re a patient, a pharmacist, or a doctor, knowing how to read it means better care and lower costs for everyone.