Ever wonder why some drugs have two names? You might see acetaminophen on a bottle in the U.S., but paracetamol on the same pill sold in Europe. Or why albuterol is in your inhaler, but your doctor from another country calls it salbutamol. These aren’t typos. They’re the result of two global systems that decide what drugs are called before they ever hit the shelf: USAN and INN. And behind them? A whole process that shapes how medicines are named - and why some names stick while others get tossed out.
What Are USAN and INN?
USAN stands for United States Adopted Names. It’s the official system used in the U.S. to give nonproprietary names to drugs. Think of it as the government’s way of making sure every drug has one clear, standardized name doctors and pharmacists can trust. The USAN Council, made up of experts from the American Medical Association, the U.S. Pharmacopeia, and the American Pharmacists Association, manages it. They’ve been doing this since 1964.
INN, or International Nonproprietary Name, is the global version. Run by the World Health Organization since 1950, INN gives drugs the same name across nearly every country. That’s why you’ll see omeprazole on a label in Japan, Brazil, or Germany - same name, same drug.
The big goal? Safety. If a doctor in New York writes a prescription for clindamycin, and a pharmacist in Sydney reads it, they both know exactly what drug is meant. No confusion. No mix-ups. That’s the whole point.
How Do These Names Work? The Stem System
Here’s where it gets clever. Both USAN and INN don’t just make up random names. They use a system built on stems - endings that tell you what the drug does.
Take -mab. If a drug ends in -mab, it’s a monoclonal antibody. That’s a type of biologic drug used to treat cancer, autoimmune diseases, and more. But it doesn’t stop there. If it ends in -ximab, like rituximab, it’s a chimeric antibody (part mouse, part human). If it ends in -zumab, like adalimumab, it’s humanized (mostly human). That’s instant classification.
Other common stems:
- -prazole - proton pump inhibitors (omeprazole, esomeprazole)
- -statin - cholesterol-lowering drugs (atorvastatin, rosuvastatin)
- -feron - interferons (interferon alfa-2a)
- -virdine - HIV drugs (efavirenz, lamivudine)
The beginning of the name - the part before the stem - is usually a made-up, catchy syllable. It’s not random. It’s designed to sound smooth, avoid sounding like other drugs, and not accidentally mean something weird in another language. For example, esomeprazole isn’t just omeprazole with an ‘e’ slapped on. The ‘es-’ tells you it’s a specific version - the S-isomer - of the original molecule. That’s chemistry in a name.
Why Do We Have Two Systems? USAN vs. INN
Here’s the twist: USAN and INN are almost the same - but not quite. About 95% of the time, they match. But there are a few stubborn differences.
Some of the most common mismatches:
- Acetaminophen (USAN) vs. Paracetamol (INN)
- Albuterol (USAN) vs. Salbutamol (INN)
- Rifampin (USAN) vs. Rifampicin (INN)
Why do these exist? History. The U.S. had its own naming practices before INN became widespread. When the WHO pushed for global standardization, the U.S. didn’t fully abandon its own terms. So now we have two names for the same drug - and that’s where problems start.
There have been real cases where patients got the wrong dose because a nurse saw salbutamol on a European label but thought it was a different drug than albuterol. The FDA doesn’t require INN names on U.S. labels - only USAN. But international travelers, imported medications, and global clinical trials can get messy.
USAN’s advantage? It’s tailored to U.S. medical culture. INN’s advantage? It’s truly global. The trade-off is a small but dangerous gap in clarity.
How a Drug Gets Its Name - The Long Road
Getting a name isn’t quick. It doesn’t happen when the drug is ready to sell. It happens early - often during Phase 1 or 2 clinical trials. That’s because the naming process takes 18 to 24 months.
Here’s how it works:
- A drug company picks 5-6 potential names. They hire specialists to check for conflicts - not just with other drugs, but with brand names, slang terms, or even words that sound like insults in other languages.
- They submit these names to both USAN and INN. The USAN Council reviews them, checks databases, and may suggest alternatives. About 30-40% of submissions need multiple rounds because of conflicts.
- Once USAN approves a name, it goes to WHO’s INN team. They either accept it or propose a different version.
- After approval, the name is published. There’s a 4-month window for public objections. If no one objects - which almost never happens - the name is official.
And here’s the kicker: about 65% of drugs that get a USAN name never make it to market. Clinical trials fail. Safety issues pop up. But the name stays in the system - available for future use.
Brand Names vs. Generic Names
Don’t confuse the generic name with the brand name. Atorvastatin is the generic. Lipitor is the brand. The generic name is public domain - anyone can use it. The brand name is trademarked. Pfizer owns Lipitor. No one else can use it.
Brand names are marketing tools. They’re catchy, easy to remember, and often tied to the drug’s benefit. Viagra sounds like vigor. Prozac sounds calming. But they’re not regulated like generic names. No stems. No rules. Just creativity - and legal teams.
That’s why you’ll see the same generic drug sold under different brand names: ibuprofen is sold as Advil, Motrin, Nuprin, and dozens of others. The generic name stays the same. The brand name changes.
What’s Changing in Drug Naming?
The old stem system was built for pills and injections. Now we have gene therapies, RNA drugs, and antibody-drug conjugates. These don’t fit neatly into -mab or -prazole.
WHO updated its monoclonal antibody naming rules in 2021 to handle newer types - like bispecific antibodies and Fc-engineered versions. USAN is working on similar updates. But it’s slow. Naming is conservative by design. You don’t want to change a system that keeps patients safe.
Still, pressure is growing. Biologics now make up 42% of global drug sales - over $380 billion in 2023. More complex drugs mean more naming challenges. Experts agree: the system works - but it’s being tested.
Why This Matters to You
If you take medication, you’re already using this system. When your pharmacist says, “This is the generic version of your brand drug,” they’re using the USAN or INN name. It’s the only way they know what’s in the pill.
And if you’re traveling? Know your drug’s INN name. If you’re prescribed albuterol in the U.S., ask for salbutamol abroad. It’s the same drug - just a different name.
Medication errors from confusing drug names cost the U.S. healthcare system about $2.4 billion a year. That’s not just money. It’s preventable harm. That’s why these naming rules exist - not for bureaucracy, but to keep you safe.
Final Thoughts
Generic drug names aren’t just labels. They’re coded messages. They tell you what the drug is, how it works, and how it’s related to others. USAN and INN are quiet heroes of modern medicine - invisible systems that make sure the right drug reaches the right person, every time.
And while brand names grab headlines, it’s the generic name that keeps the system running. The next time you see a long, odd-looking word on your prescription - remember: it’s not random. It’s science in a name.