Pain Management & Gate Control Theory
“Pain is whatever the experiencing person says it is, existing wherever they say it does.” Managing it safely means understanding how it travels — and how to block it.
Nociceptive vs neuropathic pain, the WHO Analgesic Ladder, multimodal therapy, opioid safety, and naloxone — everything you need to know.
How Pain Travels — And How to Close the Gate
Pain isn’t just a feeling — it’s a signal travelling along nerves, through the spinal cord, up to the brain. Understanding the journey changes how you treat it.
A-Delta vs C-Fibres — Two Different Messages
- A-Delta fibres: Fast, sharp, pinpointed — the immediate sting of a cut or needle. Myelinated, speedy, unmistakable.
- C-fibres: Slow, dull, burning, aching — deep, lingering, harder to place. Unmyelinated, slower, but relentless.
Gate Control Theory — Rubbing It Better Actually Works
In 1965 Melzack and Wall explained it: the spinal cord has a “gate” in the dorsal horn that decides which signals get through to the brain.
- Small pain fibres open the gate — pain passes through.
- Large touch/vibration fibres close the gate — they stimulate inhibitory cells that block pain signals. That’s why rubbing a bump, heat, ice, or TENS machines provide real relief.
Pain uses multiple pathways — so hit it from multiple angles. Paracetamol centrally, NSAIDs peripherally, opioids at spinal/brain level. Together they work better, at lower doses, with fewer side effects. Always combine where safe to do so.
The WHO Analgesic Ladder — Step Up Wisely
Start low, go slow, match the strength to the severity. Don’t jump straight to strong opioids when paracetamol will do — but don’t leave someone in severe pain because you’re afraid of morphine either.
Paracetamol & NSAIDs (Ibuprofen, Naproxen)
How they work: Paracetamol raises the pain threshold in the brain. NSAIDs block inflammation at the source — where the damage is happening.
Watch for: Paracetamol — max 4g in 24 hours, overdose damages the liver. NSAIDs — stomach irritation, kidney strain, asthma flare-ups. Always check history of ulcers and renal function.
Weak Opioids (Codeine, Tramadol)
How they work: Act on opioid receptors in the brain and spinal cord to change how pain is felt. Codeine converts to morphine in the liver — but some people can’t do that at all and get zero relief.
Watch for: Constipation — always prescribe laxatives. Nausea, drowsiness. Tramadol plus antidepressants = risk of serotonin syndrome. Codeine — some people metabolise it too fast and become dangerously sedated.
Strong Opioids (Morphine, Oxycodone, Fentanyl, Buprenorphine)
How they work: Powerful binding to mu-opioid receptors — blocks pain signals climbing to the brain. The gold standard for severe cancer and acute post-surgical pain.
Watch for — THESE CANNOT BE IGNORED:
- Respiratory depression — count breaths. If below 10–12/min: STOP, escalate, prepare naloxone.
- Constipation — opioids slow gut motility. Laxatives are NOT optional.
- Drowsiness — sedation usually drops before breathing does. Watch the patient, not just the monitor.
- Nausea — common in first few days, often settles. Anti-emetics help.
Opioid Toxicity — Recognise & Reverse
On PCA pumps, high-dose patches, or oral strong opioids — always be alert. The classic triad of overdose:
- Pinpoint pupils — won’t react to light
- Slow, shallow breathing — RR < 10 is danger
- Drowsiness → unresponsiveness → coma
Naloxone knocks the opioid off the receptors and reverses respiratory depression in minutes. Critical: naloxone wears off in 30–90 minutes — longer-acting opioids can outlast it. Patient needs monitoring, possibly repeated doses or infusion. They will wake in sudden, severe pain and withdrawal — be ready to support them.
📖 Trusted Guidelines & References
Standards to cite and share — updated and current:
- NICE CG140 — Opioids in Palliative Care (last reviewed Sep 2024) — UK framework for safe prescribing, titration, and managing side effects.
- British National Formulary (BNF) — Doses, contraindications, maximum limits, and controlled drug schedules.
- Faculty of Pain Medicine (RCoA) — Professional standards for acute and inpatient pain management.
Written by: Daniel Hancock, Registered Nurse
Focus: Pain management, opioid safety, ward monitoring
Published: September 2026 | Last reviewed: September 2026
For: UK student nurses — supervised learning only
⚠️ NICE CG140 is the current UK reference. Always confirm opioid doses, PCA settings, and naloxone protocols with the medical team — every patient is different.