Orange Book: FDA Drug Listings and Generic Drug Approval Guide

When you pick up a generic pill at the pharmacy, you might not think about how the FDA confirms it works just like the brand-name version. That’s where the Orange Book, the FDA’s official publication listing approved drug products with therapeutic equivalence evaluations. Also known as Therapeutic Equivalence Evaluations, it’s the go-to reference for pharmacists, doctors, and patients who want to know if a generic drug is truly interchangeable. This isn’t just a list—it’s a safety net. Every drug in the Orange Book has been reviewed for bioequivalence, meaning it delivers the same amount of active ingredient at the same rate as the brand-name version. No guesswork. No hidden differences.

The FDA, the U.S. government agency responsible for protecting public health through regulation of food, drugs, and medical devices updates the Orange Book daily. It includes every approved brand-name drug and its generic equivalents, along with patent and exclusivity info. That’s why you’ll see some generics listed as "AB-rated"—that’s the FDA’s green light saying they’re therapeutically equivalent. If a drug isn’t rated AB, it doesn’t mean it’s unsafe, but it might not work the same way for everyone. The therapeutic equivalence, the FDA’s classification system that determines whether generic drugs can be substituted for brand-name drugs without clinical impact rating is what matters most when your pharmacist swaps your prescription.

You’ll find this info matters most when you’re on long-term meds—like blood pressure pills, antidepressants, or seizure drugs. A small change in how a drug is absorbed can throw off your whole treatment. The Orange Book helps prevent that. It’s also why some generics are cheaper but not always interchangeable. For example, a drug like leflunomide or modafinil might have multiple generics listed, but only some carry the AB rating. That’s the difference between a safe swap and a risky one. Even though posts on this page cover topics like generic drug quality, REMS requirements, and drug interactions, they all tie back to the same foundation: knowing which drugs are truly equivalent and why.

Whether you’re switching from brand to generic, checking if your insurance will cover a cheaper option, or just wondering why your pill looks different this month, the Orange Book holds the answers. Below, you’ll find real-world guides on how generic drugs are made, how the FDA enforces standards, and how to avoid dangerous interactions—all rooted in the same system that the Orange Book makes transparent. No fluff. Just what you need to know to make smarter choices with your meds.