When you pick up a generic pill, you might wonder: FDA therapeutic equivalency codes, a system used by the U.S. Food and Drug Administration to rate whether generic drugs are truly interchangeable with brand-name versions. Also known as AB codes, these ratings determine if your pharmacist can swap your medication without asking your doctor. It’s not just paperwork—it affects whether your blood pressure med, seizure drug, or antidepressant will work the same way after a switch.
Not all generics are created equal. The FDA uses these codes to flag drugs that are therapeutically equivalent—meaning they have the same active ingredient, strength, dosage form, and, most importantly, the same effect in your body. A drug rated AB1 is considered interchangeable with the brand. But if it’s rated BN or EX, that’s a red flag. Some drugs, like phenytoin or warfarin, have a narrow window between too little and too much. Even tiny differences in how a generic is made can cause seizures, clots, or toxicity. That’s why switching generics without checking the code can be risky, especially for older adults or people with chronic conditions.
These codes are tied to another key concept: bioequivalence, the scientific standard that proves a generic drug delivers the same amount of active ingredient into your bloodstream at the same rate as the brand. The FDA doesn’t just trust manufacturers’ claims—they run real tests. But here’s the catch: bioequivalence doesn’t always guarantee clinical equivalence. That’s why some doctors and pharmacists still hesitate to switch certain drugs, even if the code says they’re interchangeable. You’ll also see these codes linked to drug interchangeability, the legal and practical ability to substitute one drug for another without losing effectiveness or safety. This matters most when you’re on Medicare, Medicaid, or insurance that pushes generics to cut costs.
What you’ll find in the posts below are real stories and hard facts about how these codes impact your health. From phenytoin switches that trigger seizures to authorized generics that quietly replace brand-name drugs, these articles show you how to read your prescription label, question substitutions, and protect yourself. You’ll learn why some medications can’t be swapped safely, how to spot when a generic might not be right for you, and what to say to your pharmacist if something feels off. This isn’t about theory—it’s about making sure the pill you take today does exactly what the one you took yesterday did.
