Opioid Special Situations
A patient on chronic morphine needs surgery. The standard postop dose barely touches the pain — not because they're drug-seeking, but because their receptors have adapted. Knowing why changes everything you do next.
Core Concept
Tolerance, physical dependence, and addiction are three distinct phenomena that students must separate cleanly. Tolerance is a pharmacologic adaptation: mu-opioid receptors downregulate with prolonged exposure, so the same dose produces less analgesia and fewer side effects over time. A tolerant patient legitimately needs higher doses. Physical dependence is a neuroadaptive state — abrupt discontinuation triggers withdrawal (diaphoresis, tachycardia, cramping, anxiety, yawning, piloerection) within 6–24 hours of the last dose. Taper opioids by 20–25% every 1–2 days to prevent this. Addiction (substance use disorder) is a behavioral pattern of compulsive use despite harm — it is NOT the same as dependence. Equianalgesia is the conversion framework for switching opioids safely. Oral morphine 30 mg ≈ oral hydromorphone 4 mg ≈ oral oxycodone 20 mg ≈ IV morphine 10 mg. When converting, reduce the calculated equianalgesic dose by 25–50% because cross-tolerance between opioids is incomplete — the new drug's receptors are fresh. Nurses must verify conversions, monitor pain scores closely during transitions, and advocate when doses seem dangerously high or inadequately low.
Watch Out For
Don't confuse physical dependence with addiction — a post-surgical patient who experiences withdrawal symptoms is dependent, not addicted. Students mistake tolerance for drug-seeking; tolerance is a predictable physiologic response, not a behavioral choice. When converting opioids, the full equianalgesic dose is NOT given — always reduce by 25–50% for incomplete cross-tolerance.
Clinical Pearl
Dependence lives in the receptors; addiction lives in the behavior. A patient can have one without the other — your assessment must distinguish them.
Test Your Knowledge
3 quick questions — see how well you understood Opioid Special Situations