Therapeutic classes are a way of classifying medical drugs according to their functions. Each therapeutic class is a group of similar medications classified together because they are intended to treat the same medical conditions. These classifications are used by doctors and pharmacists when selecting appropriate treatments for patients. Commonly used classes include analgesics, which relieve pain; antibiotics, which kill bacterial infections; and anticonvulsants, which prevent seizures.
There are many different therapeutic classes. They commonly have names that describe their intended effects, such as antipsychotics, tranquilizers, and decongestants. A therapeutic class can also be named for its chemical method of action, as is the case for classes such as dopamine receptor antagonists, which inhibit the effects of the neurotransmitter dopamine by preventing it from bonding with cells, and beta-adrenergic antagonists, more popularly known as beta blockers, which diminish the effects of adrenaline and other stress-related hormones and neurotransmitters.
Medications can also be categorized in more than one drug class, according to context. For example, a drug that can be used to treat both pain and fever, such as aspirin, may be categorized as either an analgesic or an antipyretic depending on what it is being used for.
The most commonly used organized therapeutic class system is the Anatomical Therapeutic Chemical Classification System (ATC), maintained by the World Health Organization's Collaborating Centre for Drug Statistics Methodology. The ATC classifies each drug in a series of categories, starting with a group of 14 categories organizing drugs according to the system of the body that the medication is meant to affect, such as the nervous system, immune system, or respiratory system. Drugs are then classified into broad therapeutic groups according to their function, for example, analgesics or antipsychotics. The next category indicates the drug's pharmacological or therapeutic subgroup, while the last two indicate the active ingredient's chemical group and the specific chemical used, respectively.
Each category and subcategory is represented by a letter, one or more numbers, or both, giving each medication a designation containing two letters and five numbers. Medications that have multiple uses can have multiple alphanumeric codes, one for each use. An example of an ACT code is N06AB06, which designates the drug sertraline, more commonly known by its trade name Zoloft™. Sertraline is a drug used to affect the nervous system (N) that increases the nervous system's arousal (N06) and functions as an antidepressant (N06A). It has this effect on the nervous system through increasing the amount of serotonin in the extracellular fluid outside the membranes of the patient's cells by acting as a selective serotonin uptake inhibitor (N06AB) due to the active ingredient sertraline hydrochloride.