P. David Falkenstein, PA-C, MS, DFAAPA

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Drugs are classified according to their effect on particular body systems, their therapeutic uses, and their chemical characteristics.

A class of drugs is a group of drugs that have similar characteristics; they may cure the same diseases, have similar chemical structures or work in the same way.

Example: morphine can be classified as a central nervous system depressant and a narcotic or opioid analgesic

Enables us to readily identify the similarities and differences among a large number of medications within and outside of a particular classification

One of the best and most efficient ways to master pharmacology is to become familiar with the classifications of medications and then to focus on the similarities and differences of medications within the same classification.

Prescription Drugs require a doctor's prescription before they can be purchased

Over-the-counter drugs do not require a physician's prescription before they can be purchased legally

This distinction implies the fact that prescription drugs are highly specialized and should never be taken casually

The actual distinction between prescription and over-the-counter drugs is governed by legislation

The names of therapeutic classifications usually reflect the condition for which the drugs are used (e.g., antidepressants, antihypertensives).

Sometimes, the names of many drug groups reflect their chemical characteristics rather than their therapeutic uses (e.g., adrenergics, benzodiazepines)

Many drugs fit into multiple groups because they have wide-ranging effects on the human body.

Individual drugs that represent groups of drugs are called prototypes.

Prototypes, often the first drug of a particular group to be developed, are usually the standard with which newer, similar drugs are compared.

For example, morphine is the prototype of opioid analgesics; penicillin is the prototype of antibacterial drugs.

There are 30 primary classes of drugs and numerous subdivisions

Prescription drugs can be grouped into different classification systems.

A commonly used system developed in 1959 is called the AHFS (American Hospital Formulary Service) Pharmacologic-Therapeutic Classification System.

Drugs are classified in a four-tier system.

Because of the structure of the Classification system, there are several cases where a drug can have multiple classes, either by indication, mechanism of action, or route of administration.

Additionally, drugs can also be classified 3 different ways: 

– By body system – By the action of the agents – By the drug’s mechanism of action

Drugs can also be identified or classified by one of three names: Chemical – long name, refers to the chemical

structure of the drug Generic – shorter name derived from the

chemical name Trade – brand name assigned by the

manufacturer Drugs within the same class typically have

similar sounding generic names (e.g., atenolol, metropolol, labetalol), all of which are in a drug class called beta-blockers.

Drugs are also placed into one of five drug classes, or schedules, by the DEA based on abuse according to their abuse potential, addictive nature and whether or not they have accepted medical use for treatment.

A controlled substance is placed in its respective schedule based on whether it has a currently accepted medical use in treatment in the United States and its relative abuse potential and likelihood of causing dependence.

Drugs can also be classified according to the Drug Enforcement Agency (DEA) schedules, or

By Pregnancy Category These classification systems will be

discussed in future lectures.