An analgesic, commonly called a painkiller, is a medication used to relieve pain of varying intensity and origin. Analgesics range from over‑the‑counter remedies for minor aches to prescription drugs for severe or chronic pain. For general reference on medicines, see pharmaceutical information, and for clinical definitions of pain consult pain management sources. Most analgesics exert their effect by modifying signals within the nervous system, either at the site of injury or within the brain and spinal cord.

Major classes

Clinically important groups of analgesics include:

  • Nonsteroidal anti‑inflammatory drugs (NSAIDs) — reduce inflammation and pain; examples commonly used for musculoskeletal pain and headaches.
  • Acetaminophen (paracetamol) — effective for mild to moderate pain and fever; widely available without prescription.
  • Opioids — strong central analgesics for acute severe pain and certain chronic pain conditions; examples include morphine and related drugs. See general opioid information at opioid resources.
  • Adjuvant analgesics — drugs developed for other conditions (antidepressants, anticonvulsants, topical agents) that are used to treat particular pain types such as neuropathic pain.

How they work

Analgesics act by altering pain signaling pathways. Some block the production of inflammatory mediators in peripheral tissues, while others change how pain is perceived in the central nervous system. Because these mechanisms differ, specialists choose drugs according to pain type, intensity and patient factors. Long‑term use of certain agents may lead to tolerance or dependence; the addictive potential of some analgesics is documented in clinical guidance available at addiction and dependence information.

Uses, risks and precautions

Analgesics are used in acute settings (injury, surgery), chronic pain syndromes (arthritis, cancer pain) and symptomatic relief (headache, toothache). Side effects vary: NSAIDs can increase the risk of gastrointestinal bleeding and cardiovascular effects, opioids can depress respiration and cause constipation, and overdosing on acetaminophen can cause serious liver injury. For safety and adverse effect summaries see side effect references. Specific warnings about paracetamol/acetaminophen are available at paracetamol guidance.

History and notable facts

The search for pain relief has ancient roots, from herbal remedies to the isolation of active compounds such as morphine in the 19th century and the later development of synthetic analgesics. Modern pain management emphasizes individualized treatment, balancing benefit and harm, and nonpharmacological approaches alongside drug therapy. For more detailed clinical protocols and patient information, consult professional sources linked above.