Chapter 11: Analgesic Drugs – Opioids & Nonopioids

Pain is fundamentally divided into acute pain (sudden, short duration) and persistent pain (long-term, chronic), alongside specific categories like neuropathic and cancer pain. The neurophysiology of pain, termed nociception, is explained through four interconnected processes—transduction, transmission, perception, and modulation—which are regulated by the Gate Control Theory. Pharmacological pain relief utilizes various classes of analgesics, including nonopioids (like acetaminophen, which primarily treats fever and mild pain but poses a significant risk of hepatotoxicity managed by the antidote acetylcysteine), nonsteroidal anti-inflammatory drugs (NSAIDs), and opioids. Opioids are further categorized by their receptor action: agonists (e.g., morphine, fentanyl) bind to mu receptors to produce strong analgesia; agonist–antagonists (partial agonists) cause a weaker response; and antagonists (e.g., naloxone) reverse opioid effects, crucial for managing respiratory depression and overdose. Management standards, such as the WHO three-step analgesic ladder, promote individualized care, including the use of adjuvant analgesic drugs (like anticonvulsants) often needed for neuropathic pain and the preference for around-the-clock dosing for persistent pain. Nursing care requires a holistic assessment utilizing various pain scales (e.g., FACES or Numeric), recognizing that specialized populations, such as pediatric patients and older adults, require cautious, weight-based dosing due to increased sensitivity and risk of adverse effects.