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What Does Drug Class Mean?
Depending on where you travel, the regulations surrounding drugs, controlled substances, and medications change drastically. Almost every country has its own unique set of drug classes, so it can be confusing trying to piece all the information together.
How Drug Schedules are Categorized
Most often, drugs are classified by:1
- Chemical structure (what is their chemical class?)
- Pharmacological action (where are they impacting the body?)
- Mode of action (what sort of biological impact do they make?)
- Therapeutic class (the conditions they’re intended to treat.)
- Potential for harm (likelihood for dependency, physical and mental harm, and abuse.)
- A combination of the main organ systems impacted and chemical, pharmacological, and therapeutic properties.
With so many methods to categorize drug classes and different types of controlled substances, it can be challenging to understand drug classifications.
As such, the World Health Organization recognized the need for a universal system of drug categories and classifications to ensure quality and production standards across borders.
Why Classify Drugs?
We’ve categorized drug classes since the beginning of time, starting with apothecaries and medicine men acting as the primary source of medication for health issues. However, this system didn’t allow for the globalization of medication or ensuring quality of standard in production.
More recently, drugs have been classified in systems to create a universal language for the research, production, and prescription of each substance. Additionally, drug classes ensure pharmacists produce all substances to the level of quality determined safe and effective by governing bodies.
The first global classification system was designed in 1971 by the European Pharmaceutical Market Research Association (EphMRA). The Anatomical Classification system was initially created as a tool to aid pharmacists in coding pharmaceuticals based on the drug’s active ingredient, the organ or system where the drug impacts the body, and the pharmacological, chemical, and therapeutic properties.2
World Health Organization and ATC
In 1976, EphMRA’s classification system was adopted and expanded upon by the World Health Organization Collaborating Centre for Drug Statistics Methodology (WHOCC).
Renamed the Anatomical, Therapeutic, and Chemical Classification system, the ATC now includes over 4300 different pharmaceuticals and is used to communicate medical information and drug classes worldwide.
The ATC Drug Classifications System
While it might seem complicated, the Anatomical, Therapeutic, Chemical System for classifying substances and drugs is a highly effective way of coding.
ATC classifies drugs through five levels of categorization. Each classification level provides identifying numbers or letters that combine to create a specific universal ID for drugs used around the world.
For example, consider the oral diabetic drug Metformin.
Level One: What organs/systems does this drug target?
A – Metformin impacts the alimentary tract and metabolism, so its first coded letter is A.
Level Two: What is the main therapeutic impact?
A10 – Metformin is a drug used in diabetes.
Level Three: What is the more specific pharmacological impact?
A10B – Metformin is an oral blood-glucose-lowering drug.
Level Four: What is its chemical subgroup?
A10BA – Metformin is part of the chemical subgroup Biguanides.
Level Five: What is its chemical name/substance?
A10BA02 – Metformin’s chemical name is Metformin.
Each response to these classification levels provides a number or letter that codes the substance specifically so anyone with the ID code can quickly determine the type of drug and its intended use. ATC codes are based on the impact of the drug, meaning that certain controlled substances might receive multiple codes.
USP Drug Classifications
What is the USP?
The United States Pharmacopeia (USP) is an annually published, independently reviewed scientific guide to all things pharmacology. Every drug – both human and animal, both legal and illicit – is codified and categorized in the USP.
The USP began in 1820, where a collection of physicians concerned over the quality and production of medicine banded together to codify 217 drugs and drug classes as fully as possible. The United States officially recognized the USP with the Drug Importation Act of 1848, where it was enacted to prevent the importation of low-quality and harmful medicine from drugmakers in Europe.
How Does the USP Classify Drugs?
Now, the USP contains over 4,500 monographs for prescription and over-the-counter drugs. Drug classifications are based on three categories:3
- Therapeutic category
- Pharmacologic class
- Formulary key drug types
Drugs are divided into 51 main therapeutic categories that identify the main action of the drug. These drug classifications could include anesthetics, gastrointestinal agents, or inflammatory bowel disease agents, to name a few. Within these 51 categories, the drug is then codified by its chemical makeup, followed by its main form for distribution.
What Are Drug Schedules?
Drug schedules are drug categories that sort controlled substances based on their potential levels of harm, dependency, and accepted medical use for legal settings.
In the United States, there are five schedules of drugs ranging from the most harmful and never used in medical settings (Type I) to least likely to become addictive and commonly used in prescribed medications (Type V.) They were codified in the Controlled Substance Act (CSA) of 1970 and are enforced by the DEA.
Schedule I Controlled Substances
These substances have no currently accepted medical usage. They also have the highest potential for dependency, addiction, and harm. These types of drugs include heroin, quaaludes, marijuana, LSD, and ecstasy.4
Schedule II Controlled Substances
These substances are used in medicine but with extreme prejudice. There is a very high potential for dependency, addiction, and harm. The drugs in this schedule include fentanyl, cocaine, methamphetamines, morphine, oxycodone, Ritalin, etc.4
Schedule III Controlled Substances
These substances are used for a variety of medical purposes. They still have the potential for dependency, addiction, and harm, but with a lesser likelihood than Schedule II or I. These drugs include ketamine, Vicodin, codeine, barbiturates, anabolic steroids, etc.4
Schedule IV Controlled Substances
These substances are commonly used for medical purposes and often include prescriptions that you can pick up at the pharmacy with a doctor’s note. Addiction or experiencing mental and physical harm is less likely in this schedule, although it is still possible with these types of drugs. Schedule IV substances include Xanax, Klonopin, Valium, Ativan, Darvon, etc.4
Schedule V Controlled Substances
These substances are common for many medical services, including analgesic, antidiarrheal, and antitussive purposes. These drugs contain limited amounts of narcotics in their formula. Developing an addiction or experiencing harm from them is unlikely, although never impossible when taken without a doctor’s recommendation. Schedule V substances include cough medicines with < 200 mg of codeine per 100 ml (i.e., Robitussin AC, Phenergan with codeine), Ezogabine, etc.4