Drug class

A drug class is a set of medications that have similar chemical structures, the same mechanism of action (i.e., bind to the same biological target), a related mode of action, and/or are used to treat the same disease.

In several dominant drug classification systems, these four types of classifications form a hierarchy. For example, the fibrates are a chemical class of drugs (amphipathic carboxylic acids) that share the same mechanism of action (PPAR agonist), mode of action (reducing blood triglycerides), and are used to prevent and to treat the same disease (atherosclerosis). Conversely not all PPAR agonists are fibrates, not all triglyceride lowering agents are PPAR agonists, and not all drugs that are used to treat atherosclerosis are triglyceride lowering agents.

The most widely used drug classification system is the Anatomical Therapeutic Chemical Classification System (ATC). The Systematized Nomenclature of Medicine (SNOMED) also includes a section devoted to drug classification.

Chemical class

Examples of drug classes that are based on chemical structures include:

• β-lactam antibiotic
• Benzodiazepine
• Cardiac glycoside
• Fibrate
• Thiazide diuretic

Mechanism of action

Drug classes that share a common molecular mechanism of action by modulating the activity of a specific biological target. The definition of a mechanism of action also includes the type of activity at that biological target. For receptors, these activities include agonist, antagonist, inverse agonist, or modulator. Enzyme target mechanisms include activator or inhibitor. Ion channel modulators include opener or blocker. The following are specific examples of drug classes whose definition is based on a specific mechanism of action:

• 5-Alpha-reductase inhibitor
• Angiotensin II receptor antagonist
• ACE inhibitor
• Alpha-adrenergic agonist
• Beta blocker
• Dopamine agonist
• Dopamine antagonist
• Incretin mimetic
• Nonsteroidal anti-inflammatory drug − cyclooxygenase inhibitor
• Proton-pump inhibitor
• Renin inhibitor
• Selective glucocorticoid receptor modulator
• Selective serotonin reuptake inhibitor
• Statin – HMG-CoA reductase inhibitor

Mode of action

Drug classes that are defined by common cellular mode of action include:

• Diuretic
• Cholinergic
• Dopaminergic
• GABAergic
• Serotonergic

Therapeutic class

Drug classes that are defined by their therapeutic use include:

• Analgesic
• Antibiotic
• Anticoagulant
• Antidepressant
• Anticancer
• Antiepileptic
• Antipsychotic
• Antiviral
• Sedative

Amalgamated classes

Some drug classes have been amalgamated from these three principles to meet practical needs. The class of non-steroidal anti-inflammatory drugs (NSAIDs) is one such example. Strictly speaking, and also historically, the wider class of anti-inflammatory drugs also comprises steroidal anti-inflammatory drugs. These drugs were in fact the predominant anti-inflammatories during the decade leading up to the introduction of the term "non-steroidal anti-inflammatory drugs". Because of the disastrous reputation that the corticosteroids had got in the 1950s, the new term, which offered to signal that an anti-inflammatory drug was not a steroid, rapidly gained currency. The drug class of "non-steroidal anti-inflammatory drugs" (NSAIDs) is thus composed by one element ("anti-inflammatory") that designates the mechanism of action, and one element ("non-steroidal") that separates it from other drugs with that same mechanism of action. Similarly, one might argue that the class of disease-modifying anti-rheumatic drugs (DMARD) is composed by one element ("disease-modifying") that albeit vaguely designates a mechanism of action, and one element ("anti-rheumatic drug") that indicates its therapeutic use.

• Nonsteroidal anti-inflammatory drug (NSAID)
• Disease-modifying antirheumatic drug (DMARD)