Analgesics: Mechanism, Uses, Side Effects.

August 7, 2025

Analgesic Overview

Analgesic also known as Painkiller are those that reduce the sensation of pain. Pain is not a disease but a by-product of a disease. Sometimes it is short-lived in a condition and sometimes it is life-long.

Example:- Tooth Pain (short time), Rheumatoid Arthritis(life long pain)

Type of Analgesics

Analgesics are the mainly divided into the two parts:

Opioids: These Drugs are derived from the opium such as morphine.
Non-opioids: This includes all other than opioids like paracetamol, nefopam and also the NSAIDs.

Mechanism of Action

As you have seen there are two types of analgesics, and both work in different ways.

Opioids Drugs: These Drugs works on CNS and spinal cord that binds to the opioids receptor like mu(μ), kappa(κ) and delta(δ), and binding to these receptor signal blocks between the brain cells that reduces the pain.

Non-Opioid Drugs: These drugs directly works on the site of pain. The drugs of this group works on the COX-1(cyclooxygenase-1) and COX-2(cyclooxygenase-2) enzymes. NSAIDs Drugs block the action of COX enzyme that reduce the conversion of arachidonic acid into prostaglandins, PGs is the responsible for the inflammation and pain sensation.

Therapeutic Use

Analgesics are primarily used to relieve pain without affecting consciousness. They are used depending on the type of pain and the intensity of the pain.

Headache and Migraine – Mild analgesics like paracetamol or NSAIDs.
Muscle and Joint Pain – Ibuprofen, diclofenac for inflammation and pain
Toothache and Dental Procedures – Fast-acting analgesics to control sharp pain
Post-operative Pain – Opioids like morphine used for moderate to severe pain
Arthritis and Bone Disorders – Long-term use of NSAIDs for chronic pain
Menstrual Cramps (Dysmenorrhea) – Paracetamol or mefenamic acid
Cancer Pain – Strong opioids for continuous or breakthrough pain

Side Effects of Analgesics

Non-Opioid Analgesics (e.g. Paracetamol, NSAIDs)

Gastric Irritation – Especially with NSAIDs like ibuprofen or aspirin, long-term use can damage the stomach lining.
Liver Damage – Overdose of paracetamol can cause serious liver toxicity.

Opioid Analgesics (e.g. Morphine, Codeine)

Constipation – Common with long-term use due to reduced gut motility.
Respiratory Depression – High doses can slow down breathing, potentially life-threatening.
Dependence and Tolerance – Regular use can lead to physical dependence and reduced effect over time.

Pregnancy Category

NSAIDs: Use with caution, especially during the third trimester, as they may affect foetal circulation and labour.
Paracetamol: Generally considered safe during pregnancy when used in recommended doses.

⚠ Disclaimer

The content provided in this blog is for educational and informational purposes only. It should not be taken as medical advice. Always consult a licensed healthcare professional before starting, changing, or stopping any medication. Treatment decisions should be based on a doctor’s evaluation of your individual health status and medical history.