analgesics

Analgesics are medications designed to relieve pain without causing loss of consciousness. They encompass several drug classes: non-opioid analgesics such as acetaminophen and nonsteroidal anti-inflammatory drugs (NSAIDs) including ibuprofen and naproxen, as well as selective COX-2 inhibitors; opioid analgesics such as morphine, oxycodone, fentanyl, and hydromorphone; and adjuvant analgesics, including antidepressants (eg, amitriptyline, duloxetine), anticonvulsants (eg, gabapentin, pregabalin), topical agents, and local anesthetics. They are used for a range of acute and chronic pain conditions and may be given alone or in combination.

Mechanisms and use vary by class. Non-opioids reduce pain chiefly by decreasing prostaglandin synthesis and inflammation; acetaminophen provides analgesia and antipyresis with less anti-inflammatory effect. Opioids act on mu-opioid receptors to alter pain perception and emotional response but carry risks of sedation, respiratory depression, constipation, and dependence. Adjuvants may enhance analgesia or treat neuropathic pain and other pain syndromes. Medications can be administered orally, topically, transdermally, intravenously, or intramuscularly, depending on the clinical scenario.

Safety and cautions: NSAIDs can cause gastrointestinal ulcers, bleeding, kidney impairment, and should be used cautiously in renal disease or peptic ulcers. Acetaminophen overdose can cause severe liver injury. Opioids can cause respiratory depression, constipation, nausea, sedation, and may lead to tolerance or dependence with prolonged use. Drug interactions with alcohol or other central nervous system depressants, and considerations for pregnancy, children, elderly, or liver/kidney disease, are important in planning therapy.

Practice considerations: Multimodal analgesia combines agents with different mechanisms to improve relief and reduce side effects. The WHO analgesic ladder offers a framework for cancer pain but modern practice tailors regimens to individual pain type, severity, and comorbidities, with dose adjustments for hepatic or renal impairment.