Drug class
A group of drugs sharing chemical, pharmacological, or therapeutic properties.
A drug class is a grouping of medications and other compounds that share certain characteristics, such as similar chemical structures, the same mechanism of action (binding to the same biological target), comparable modes of action, or use in treating similar diseases. In the United States, the Food and Drug Administration’s Center for Drug Evaluation and Research classifies new medications by both their chemical and therapeutic categories. Typically, a drug class is defined by a prototype drug—the most important and often the first developed in that class—which serves as a reference for comparison.
In major classification systems, these types of groupings are arranged hierarchically. For instance, fibrates form a chemical class (amphipathic carboxylic acids) that share a mechanism of action (PPAR agonist), a mode of action (lowering blood triglyceride levels), and a therapeutic use (preventing and treating atherosclerosis). However, not all PPAR agonists are fibrates, not all triglyceride-lowering agents are PPAR agonists, and not all drugs for atherosclerosis lower triglycerides.
Several comprehensive systems exist. The Anatomical Therapeutic Chemical Classification System (ATC) combines organ system, therapeutic, pharmacological, and chemical properties into five levels. The Systematized Nomenclature of Medicine (SNOMED) includes a section for drug classification.
Drug classes can be defined from different perspectives. Chemical class categorizes drugs by their chemical structure. Mechanism of action categorizes them pharmacologically by their biological target, including the type of activity—such as agonist, antagonist, inverse agonist, or modulator for receptors; activator or inhibitor for enzymes; and opener or blocker for ion channels. Mode of action categorizes drugs biologically by the anatomical or functional change they induce. Therapeutic class categorizes them medically by the pathology they treat.
Some drug classes are amalgamated from these principles to meet practical needs. For example, nonsteroidal anti-inflammatory drugs (NSAIDs) combine the mechanism-of-action element “anti-inflammatory” with the element “nonsteroidal,” which distinguishes them from steroidal anti-inflammatory drugs. Similarly, disease-modifying antirheumatic drugs (DMARDs) combine a vaguely defined mechanism-of-action element (“disease-modifying”) with a therapeutic-use element (“anti-rheumatic drug”).
Other classification systems exist, such as the Biopharmaceutics Classification System, which categorizes drugs by solubility and intestinal permeability. Legal classification varies by jurisdiction—for example, Canada’s Controlled Drugs and Substances Act, the UK’s Misuse of Drugs Act, and the US Controlled Substances Act schedules. Pregnancy category definitions also differ across jurisdictions.
- definition
- Group of medications sharing chemical structure, mechanism of action, mode of action, or therapeutic use
- classification types
- Chemical, mechanism of action, mode of action, therapeutic class
- example class
- Fibrates (chemical class: amphipathic carboxylic acids; mechanism: PPAR agonist; mode: reducing blood triglycerides; therapeutic: treating atherosclerosis)
- classification systems
- Anatomical Therapeutic Chemical Classification System (ATC), Systematized Nomenclature of Medicine (SNOMED), Biopharmaceutics Classification System
- legal classifications
- Canadian Controlled Drugs and Substances Act, UK Misuse of Drugs Act, US Controlled Substances Act schedules, pregnancy category systems
Lore & Background
Drug classes are groups of medications and other compounds that share similar chemical structures, act through the same biological target (mechanism of action), produce similar functional or anatomical changes (mode of action), or are used to treat similar diseases (therapeutic use). In the United States, the Food and Drug Administration’s Drug Evaluation and Research Center classifies new medications based on both their chemical and therapeutic classes. A drug class is typically defined by a prototype drug—the most important and often the first developed within the class—which serves as a reference for comparison. Major classification systems organize these four types into hierarchies. For example, fibrates are a chemical class (amphipathic carboxylic acids) that share a mechanism of action (PPAR agonist), a mode of action (reducing blood triglyceride levels), and a therapeutic use (preventing and treating atherosclerosis). However, not all PPAR agonists are fibrates, not all triglyceride-lowering agents are PPAR agonists, and not all drugs for atherosclerosis lower triglycerides. Comprehensive systems include the Anatomical Therapeutic Chemical Classification System, which combines organ system, therapeutic, pharmacological, and chemical properties into five levels, and the Systematized Nomenclature of Medicine, which includes a drug classification section. Some classes are amalgamated from multiple principles, such as nonsteroidal anti-inflammatory drugs (NSAIDs), which combine a mechanism-of-action element (“anti-inflammatory”) with a chemical distinction (“nonsteroidal”) to separate them from steroidal anti-inflammatory drugs, a distinction that gained currency after the reputation of corticosteroids in the 1950s. Similarly, disease-modifying antirheumatic drugs (DMARDs) blend a vaguely defined mechanism (“disease-modifying”) with a therapeutic use (“anti-rheumatic drug”). Other systems, like the Biopharmaceutics Classification System, classify drugs by solubility and intestinal permeability. Legal classifications vary by jurisdiction, including the Canadian Controlled Drugs and Substances Act, the UK Misuse of Drugs Act, and US pregnancy category systems.
Reader's Guide
The concept of drug class is fundamental to pharmacology and medicine, enabling systematic categorization of medications for research, prescribing, and regulation. Four primary classification types: chemical structure, mechanism of action (biological target and activity type, such as agonist or inhibitor), mode of action (anatomical or functional change induced), and therapeutic use (pathology treated). Some classes are amalgamated from these principles, such as nonsteroidal anti-inflammatory drugs (NSAIDs), which combine a mechanism-of-action element ('anti-inflammatory') with a distinguishing element ('nonsteroidal') to separate them from steroidal anti-inflammatory drugs. Similarly, disease-modifying anti-rheumatic drugs (DMARDs) blend a vague mechanism-of-action term ('disease-modifying') with a therapeutic-use term ('anti-rheumatic drug'). The article notes that the term NSAID gained currency in the 1950s due to the disastrous reputation of corticosteroids. Drug classification systems like the Anatomical Therapeutic Chemical Classification System (ATC) and Systematized Nomenclature of Medicine (SNOMED) provide comprehensive frameworks, while legal classifications vary by jurisdiction, including the US Controlled Substances Act schedules and pregnancy category systems.
Did You Know?
- Fibrates are a chemical class of drugs (amphipathic carboxylic acids) that share the same mechanism of action (PPAR agonist) and are used to treat atherosclerosis.
- The class of nonsteroidal anti-inflammatory drugs (NSAIDs) is an amalgamated class combining a mechanism-of-action element ('anti-inflammatory') with a distinguishing element ('nonsteroidal').
- The term 'nonsteroidal anti-inflammatory drugs' gained currency in the 1950s because of the disastrous reputation that corticosteroids had acquired.
- Drug classes are typically defined by a prototype drug, the most important and often the first developed drug within the class.
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