analgesic
Meaning of analgesic: The classes act at different points along the pain pathway, which is why one may help where another does nothing.
Definition of analgesic
An analgesic is a medicine that relieves pain without switching off consciousness or general sensation. The main groups are the nonopioid pain relievers such as acetaminophen, the nonsteroidal anti-inflammatory drugs, and the opioids, with several further classes used mainly for nerve pain. Each acts at a different point between the injured tissue and the brain, and each carries its own risks.
What are the main classes?
| Class | Where it acts | Pain it suits |
|---|---|---|
| Nonopioid, such as acetaminophen | Mainly within the brain and spinal cord | Mild to moderate pain, and fever |
| Nonsteroidal anti-inflammatory drug | Blocks the enzymes that make inflammatory messengers at the site of injury | Pain accompanied by inflammation or swelling |
| Opioid | Binds receptors in the brain and spinal cord that damp the incoming signal | Moderate to severe pain, including after surgery |
| Adjuvant, including certain antidepressants and antiseizure medicines | Quiets overactive nerve signaling | Burning or shooting pain from damaged nerves |
Local anesthetics belong in the same conversation even though they are not usually counted as analgesics. They stop the signal in the nerve itself, which is why numbing an area produces relief no tablet can match, and why the effect ends abruptly rather than fading.
Why does the type of pain matter so much?
Pain from a sprained ankle, pain from a tumor pressing on bone and pain from a damaged nerve are carried and processed differently, so a medicine aimed at one may do very little for another. An anti-inflammatory works best where inflammation is generating the signal. A medicine for nerve pain does little for a fresh injury. Severe acute pain after an operation is often managed by combining classes, so that lower doses of each can be used and their side effects do not stack up in the same organ.
What does an analgesic not do?
It does not repair the cause. Pain that is masked continues to signal something, and relief without an explanation leaves the underlying problem unaddressed. Nor does an analgesic abolish sensation the way an anesthetic does: touch, pressure and temperature remain. Effects also differ sharply between classes. Nonsteroidal drugs can irritate the stomach lining, affect kidney function and raise blood pressure; acetaminophen is gentler on the stomach but damages the liver in excess, including through the several combination products that quietly contain it; opioids cause constipation, drowsiness and slowed breathing, and tolerance and dependence develop with continued use.
Also known as
Used in a sentence
A nonopioid analgesic was recommended for mild postoperative pain.
Good to know
The safest analgesic and dose depend on the type of pain, the person's medical history, and the other medicines being taken, so the classes are not interchangeable.
Word origin
Where “analgesic” comes from
From Greek an-, meaning without, and algesis, meaning sense of pain.