Analgesics | What Are Analgesics and How They Are Classified?

What Are Analgesics

Analgesics, also known as painkillers, are a class of drugs that are generally used to reduce or relieve pain, an unlikable emotional and sensory experience in a human body linked with potential or actual tissue damage, or expressed in terms of such damage. The term “Analgesic” is derived from two Greek words – (1) an ("without") and (2) algos ("pain").

In other words, an analgesic is a medicinal agent, which relieves or reduces pain by heightening the threshold level in a body, without hampering consciousness or varying other sensory modalities. In short, therapeutic substances that diminish or reduce pain are termed as analgesics.

Classification of Analgesics

Drugs that are included in analgesics work in diverse ways to diminish or relieve pain. They act mainly on the central and peripheral nervous system. Narcotic drugs such as pathedine, synthetic drugs such as ketorolac, the non-steroidal anti-inflammatory drugs (NSAIDs) such as the salicylates (aspirin), and a variety of drugs are included in analgesics. However, there are a few exceptions too. For example, tri-cyclic antidepressants and anticonvulsants are frequently used to treat neuropathic pain syndromes, but these drugs are not considered in analgesics.

Based on the narcosis properties of the analgesic drugs, analgesics can be classified into the following groups.


The narcotic analgesics are the agents that cause sleep or loss of consciousness (narcosis) in conjunction with their analgesic effect. In other words, drugs that directly act on central nervous system (CNS) to relieve pain are termed as narcotic analgesics. In addition, the term narcotic becomes associated with the addictive properties of opioids and other CNS depressant agents. The opiates and the derivatives of opiates (i.e. opioids) are the most frequently used narcotic analgesics. For this reason, in United States, these analgesics are also known as opioid analgesics (e.g. morphine, codeine, pathedine, etc).

Learn more about Weak and Strong Opioids.

Non-narcotic analgesics

The non-narcotic analgesics act peripherally on the nervous system to reduce pain. Excluding the analgesic effect, the non-narcotic analgesics usually have two other properties (antipyretic and anti-inflammatory effects). Unlike narcotic analgesics, drugs of this class do not cause physical dependencies and narcosis. However, most of the drugs in this class are gastric irritant. For this reason, physicians generally recommend an antacid or anti-ulcerent when prescribing these drugs. Most often, these drugs are used in the management of mild to moderate pain. Usually, they are available as OTC (over the counter) drugs in most drug stores.

Learn more about How the Nervous System Works.

Non-steroidal anti-inflammatory drug (NSAID)

Another class of analgesic drug is the NSAIDs or the non-steroidal anti-inflammatory drugs. Drugs of this class not only show chemical dissimilarities but also vary in their analgesic, antipyretic and anti-inflammatory properties. These drugs work principally by inhibiting the COX1 and COX2 enzymes. However, they do not act on the lipooxygenase enzymes. Aspirin, the most widely used analgesic, is a prototype of this class.
Published on: November 02, 2011
Last Updated: January 01, 2013

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