Pain Management Pharmacology: Opioid Receptors and the LPN Role
Pain medications act on specific receptor locks throughout the nervous system. The opioid class is the most high-yield for the NCLEX-PN because it carries the most safety responsibilities and the most frequently tested adverse effects. Understanding which receptor is targeted and what that receptor does predicts every clinical cue associated with opioid use.
| Receptor | Location | Effect When Opioid Binds | Clinical Cue If Overstimulated |
|---|---|---|---|
| Mu (μ) | Brain, spinal cord, GI tract | Analgesia, euphoria, sedation, ↓ GI motility, respiratory depression | Pinpoint pupils, RR <12, sedation, constipation |
| Kappa (κ) | Brain, spinal cord | Analgesia, sedation, dysphoria | Confusion, disorientation |
| Delta (δ) | Brain, peripheral nerves | Analgesia, mood effects | Contributes to dependence pathway |
Before giving: Assess (collect) respiratory rate. Hold and report if RR <12 breaths/min. Note level of sedation — oversedation precedes respiratory depression.
Three priority cues to report immediately: Respiratory rate <12, pinpoint pupils, unresponsive to verbal stimuli. These = opioid overdose pattern. Naloxone (Narcan) reverses opioid effects by blocking mu receptors — must be available wherever opioids are used.
Constipation is NOT optional: Every patient on scheduled opioids should have a bowel regimen ordered. Constipation does not develop tolerance — it persists throughout opioid use. Note last bowel movement and report if >3 days.
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