analgesic

An analgesic is a medication that relieves pain without causing loss of consciousness. Analgesics are used to manage acute and chronic pain and, in some cases, fever. They work by interrupting pain signaling at various points in the nervous system and are chosen based on the type and intensity of pain, patient factors, and potential risks.

Analgesics are commonly classified as non-opioid, opioid, and adjuvant. Non-opioid analgesics include acetaminophen (paracetamol) and non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, naproxen, and aspirin. These drugs often reduce pain and inflammation and may also lower fever. Opioid analgesics, such as morphine, codeine, oxycodone, and fentanyl, act on opioid receptors to blunt pain signals and can cause sedation, euphoria, and risk of dependence. Adjuvant analgesics, including certain antidepressants (amitriptyline, duloxetine), anticonvulsants (gabapentin, pregabalin), and topical agents (lidocaine, capsaicin), are used to enhance analgesia, particularly for neuropathic pain or complex cases.

Mechanisms vary by class. Acetaminophen is believed to act centrally to reduce pain and fever. NSAIDs inhibit cyclo-oxygenase enzymes, decreasing prostaglandin synthesis and inflammation. Opioids modulate pain pathways at spinal and brain levels. Adjuvant agents modify neurotransmitter activity to improve pain control or reduce analgesic requirements.

Safety and dosing depend on the drug and patient. Acetaminophen has a liver toxicity risk at high doses; NSAIDs can cause gastrointestinal, renal, and cardiovascular issues; opioids carry risks of respiratory depression, sedation, tolerance, and dependence. Use is guided by clinical indications, comorbidities, and current therapies.