Generic Drug Naming Explained: USAN, INN, and How Brand Names Are Chosen

• DATE: 2 12 25
• BY: Clive Smart

Ever wonder why some drugs have two names? One sounds like a science experiment-albuterol-and the other like something you’d hear in a British hospital-salbutamol? Or why omeprazole ends in ‘-prazole’ while atorvastatin ends in ‘-statin’? It’s not random. There’s a whole system behind how drugs get their generic names, and it’s designed to keep you safe.

Why Generic Names Even Exist

Every drug has two names: a brand name and a generic name. The brand name is what the company sells it under-like Advil or Lipitor. The generic name is the official, public-domain label for the active ingredient. That’s where USAN and INN come in.

Generic names aren’t just for doctors and pharmacists. They’re used in prescriptions, medical records, insurance forms, and drug labels. If two drugs have similar names, someone could mix them up. A patient might get the wrong dose. A nurse might give the wrong drug. That’s why these names aren’t chosen by marketing teams-they’re chosen by scientists, pharmacists, and regulators to be clear, unique, and meaningful.

USAN: The American Standard

In the United States, the United States Adopted Names (USAN) program handles generic naming. It’s been around since 1964 and is run by a council made up of the American Medical Association, the American Pharmacists Association, and the United States Pharmacopeia.

When a drug company develops a new medicine, they can’t just pick any name. They submit up to six name options to the USAN Council. The council checks each one for conflicts with existing drug names, trademark issues, and even how it sounds in different dialects of English. They want to avoid names that sound like other drugs. For example, they wouldn’t approve a name that sounds too close to “hydralazine” if there’s already a “hydroxyzine” on the market.

Once USAN picks a name, it becomes the official generic name for use in the U.S. The FDA requires it on all drug labels sold here. But here’s the twist: USAN doesn’t automatically accept the international name. That’s where INN comes in.

INN: The Global Standard

Outside the U.S., most countries follow the International Nonproprietary Name (INN) system, managed by the World Health Organization since 1950. The goal? One name for one drug, no matter where you are.

INN names are designed to be understood by doctors in Tokyo, Toronto, and Tanzania. The WHO works with national naming bodies-including USAN-to align names as much as possible. About 95% of the time, USAN and INN match. But not always.

Take acetaminophen. In the U.S., that’s the name. Everywhere else? It’s paracetamol. Albuterol in the U.S. is salbutamol in Europe. Rifampin in the U.S. is rifampicin abroad. These aren’t typos. They’re historical differences that stuck.

These small mismatches cause real problems. There have been documented cases where international travelers got the wrong medication because their prescription used a different name. That’s why pharmacists are trained to recognize both versions.

The Secret Code: Stems and Prefixes

Here’s where it gets clever. Both USAN and INN use a system of stems-the ending part of the name-that tells you what the drug does.

• -prazole = proton pump inhibitor (omeprazole, pantoprazole)
• -statin = cholesterol-lowering drug (atorvastatin, rosuvastatin)
• -mab = monoclonal antibody (rituximab, adalimumab)
• -virdine = HIV antiviral (zidovudine, lamivudine)
• -feron = interferon (interferon alfa-2a)

Once you know the stem, you know the class. That’s huge in emergency situations. If a patient has a reaction to a drug ending in “-mab,” a doctor immediately knows it’s an immune-targeting biologic.

There are also sub-stems for more detail. For monoclonal antibodies:

• -ximab = chimeric (part mouse, part human)
• -zumab = humanized (mostly human)
• -umab = fully human

The first part of the name-the prefix-is usually made up. It doesn’t mean anything. “Ome-” in omeprazole? Just a sound that’s easy to say and remember. “Ator-” in atorvastatin? No hidden meaning. It’s there to make the name unique.

There are also prefixes that tell you about chemical structure:

• es- = the S-isomer (esomeprazole is the more effective version of omeprazole)
• lev- = the left-handed version of a molecule (levofloxacin)
• dex- = the right-handed version (dextromethorphan)

This level of detail helps doctors understand subtle differences between drugs that might look identical at first glance.

How Brand Names Are Chosen (And Why They’re So Weird)

Brand names are a whole different game. They’re created by marketing teams, not scientists. Their job? To be memorable, catchy, and legally ownable.

Companies spend millions testing brand names. They run focus groups. They check trademarks in every country. They even test how the name sounds when spoken by someone with a thick accent.

That’s why you get names like Prozac, Viagra, or Humira. They’re not based on chemistry. They’re designed to stick in your mind. “Viagra” sounds like “vigor” and “Niagara.” “Prozac” sounds like “proactive.” “Humira” sounds like “human” and “miracle.”

But here’s the catch: brand names can’t be too similar to generic names. You can’t call your new drug “Omeprazole Plus.” That would confuse people and break the rules. So companies get creative. They use made-up words, add suffixes like “-XR” for extended release, or combine syllables from the generic name with something emotional.

And yes, many names get rejected. One company once submitted 20 different names for a single drug before finding one that passed trademark checks and didn’t sound like a toilet cleaner in another language.

Why This System Matters

This isn’t just about labels. It’s about safety.

The U.S. healthcare system spends about $2.4 billion a year treating errors caused by drug name confusion. That’s not just mistakes-those are hospitalizations, overdoses, allergic reactions. A drug named “Lanoxin” (brand) and “digoxin” (generic) might seem far apart, but if a handwritten prescription looks like “digoxin” but gets read as “Lanoxin,” the dose could be wrong.

The stem system helps prevent this. If a doctor sees “-prazole,” they know it’s a stomach acid reducer. If they see “-mab,” they know it’s a biologic that affects the immune system. That’s faster than looking up a database.

Even with all the rules, mistakes happen. New drugs like gene therapies and RNA-based treatments don’t fit neatly into old stems. The WHO and USAN are working on new guidelines, but it’s complicated. You can’t just slap a “-rna” suffix on everything.

What You Should Know as a Patient

You don’t need to memorize all the stems. But here’s what helps:

• If your prescription says “generic,” it’s the same active ingredient as the brand name-just cheaper.
• Always check the generic name on the bottle. If you’re traveling, know both the U.S. and international versions.
• If you’re confused by a name, ask your pharmacist. They’re trained to spot name mix-ups.
• Don’t assume a brand name means it’s better. Generic drugs go through the same safety checks.

Drug naming might seem like boring bureaucracy. But it’s one of the quietest, most effective safety nets in medicine. Every time you pick up a bottle and see a name like “metformin” or “lisinopril,” you’re seeing decades of science, language, and patient safety built into a single word.