How Do Drugs Get Their Names?

Most drugs on the market have 2 names. They have a brand name (like Tylenol), and a generic name (like acetaminophen). Unlike brand names, generic names are used to describe a drug's function.1

The International Union of Pure and Applied Chemistry (IUPAC) name for a drug describes its structure. However, these names can be long or complicated. Therefore, a clear and consistent naming system is used.

What is the process for choosing a drug name?

There are many steps to naming a new drug. The United States Adopted Names program (USAN) assigns generic names to all active ingredients in drugs. The USAN program names active ingredients in many things. They name ingredients in drugs and vaccines, and even sunscreen or contact lenses.1

USAN sends name recommendations to the World Health Organization (WHO) naming program. This is called the International Nonproprietary Names (INN) program. INN then makes the final call on whether a drug name is approved or not.1

Assigning a name to a drug is a key step in the development process. USAN and INN make sure drug names are the same both inside and outside the United States. These organizations work together for public safety.1

Having clear naming rules for drugs makes it easier to identify and classify them. It also makes it easier to avoid confusion when people take different drugs.

General naming rules

Drug names have 2 main parts:1

  • Stem – This describes the drug's class or function. It also defines the chemical structure or how the drug works.
  • Affix – This distinguishes between drugs in the same class or that work the same way.

Stems and affixes are important to drug names. They have to be distinct enough from each other to avoid confusion between drugs.2

USAN and INN also look at global needs. For example, drug names cannot include the letters H, J, K, or W. This is because these letters are pronounced differently between languages.1

A name that is fine in English may have a different meaning or even be obscene in another language. This is important to avoid confusion or offense.

Finally, drug names cannot use company names or medical terms. Company names are considered marketing, which is off-limits. Words like "best" or "better" cannot be used for the same reason. Medical terms are not allowed because a drug may be used to treat several conditions, not just the one it was originally approved for.3

Common drug stems and what they mean

Drugs have a wide variety of stem meanings, ranging from broad classes to specific actions. Some of these stems include:4

  • -mab: Monoclonal antibodies, such as cetuximab
  • -prazole: Antiulcer agents, such as omeprazole
  • -olone: Steroids, such as prednisolone
  • -formin: Hypoglycemics, such as buformin
  • -carbef, -cillin, -gillin, -micin, -mycin, -oxef, -tricin: Antibiotics, such as penicillin

These are not the only stems a drug name can have. The National Library of Medicine website provides more information about drug stem meanings.

Monoclonal antibody naming rules

Monoclonal antibodies are used to treat a variety of conditions. These include migraines and some types of cancer. All monoclonal antibody drugs end in -mab. However, they have additional naming rules.5,6

The syllable right before -mab stands for the source of the antibody structure. Examples include:5

  • -o-: The antibody structure is nearly 100 percent the same as a mouse antibody.
  • -xi-: The antibody structure is similar to humans and other organisms.
  • -zu-: The antibody structure is 90 percent human-like.
  • -u-: The antibody structure is fully human.

Right before this syllable is the syllable that stands for the drug's use. These may not match up with clinical use. Instead, they match with the original target of the drug while it was in development. Examples include:5

  • -ci-: Drugs that affect the circulatory system
  • -tu- or –tum-: Drugs used to treat cancer
  • -li-: Drugs that impact the immune system

CGRP monoclonal antibodies are used to prevent migraines. They have an additional 4 letters at the end of their names, such as eptinezumab-jjmr. CGRP antibodies are biological drugs. This means they come from cells of living organisms.6

Biologics can have similar drugs that share a function but are different from each other. This is called a biosimilar. A biologic-biosimilar pair will have the same generic name. However, they will have different 4-letter suffixes. This is to distinguish between the 2 drugs.6

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