WHO Analgesic Ladder & Clinical Pain Management Protocols

The Four-Step WHO Analgesic Ladder Framework

Originally promulgated by the WHO in 1986 for cancer pain, Modern clinical practice expands this into a 4-step model integrating interventional procedures.

Step Level

Pain Severity

Pharmacological Agents

Key Exam Takeaways

Step 1

Mild Pain
(VAS 1–3)

Non-Opioids:
• Paracetamol
• NSAIDs (Aspirin, Ibuprofen, Naproxen, Celecoxib)
± Adjuvants

• No physical dependence/addiction.
• Ceiling effect present.
• Paracetamol acts centrally; NSAIDs inhibit peripheral COX.

Step 2

Mild to Moderate Pain
(VAS 4–6)

Weak Opioids:
• Codeine
• Dihydrocodeine
• Tramadol
± Non-Opioids ± Adjuvants

• Known ceiling effect for analgesia.
• Codeine is a prodrug requiring CYP2D6 activation to morphine.


• Co-codamol combinations increase efficacy.

Step 3

Moderate to Severe Pain
(VAS 7–10)

Strong Opioids:
• Morphine (1st line)
• Oxycodone
• Fentanyl
• Hydromorphone
• Methadone
± Non-Opioids ± Adjuvants

• NO ceiling effect for analgesia (titrate to relief or toxicity).
• Active metabolites: Morphine-6-glucuronide (M6G), M3G.
• Co-prescribe stimulant laxatives.

Step 4

Severe / Refractory Interventional

Interventional Therapies:
• Nerve blocks
• Epidural/Intrathecal pumps
• Neurolysis
• Spinal cord stimulation

• Indicated when oral/systemic pharmacotherapy is insufficient or limited by intolerable toxicity.



3. Drug Profiles

Paracetamol (Acetaminophen)

• Mechanism: Inhibits central prostaglandin synthesis in the CNS with negligible peripheral anti-inflammatory activity. Excellent antipyretic and analgesic properties.
• Dosing: Standard adult dose 500–1000 mg QDS (every 4–6 hours; max 4000 mg/24 hr).
• Toxicity: Overdose depletes hepatic glutathione, causing accumulation of the toxic reactive metabolite N-acetyl-p-benzoquinoneimine (NAPQI), leading to centrilobular hepatic necrosis. Antidote = N-acetylcysteine (NAC).
• Utility: Can be maintained across ALL steps of the WHO ladder to provide opioid-sparing benefits.

NSAIDs (Cyclooxygenase Inhibitors)

• Mechanism: Inhibit cyclooxygenase (COX-1 and COX-2) enzymes, preventing conversion of arachidonic acid to PGE2, PGI2, and TXA2. PGE2 inhibition reduces peripheral nociceptive terminal sensitization.

• Non-Selective vs Selective COX-2: COX-1 inhibition causes gastric mucosal breakdown and ulceration. Selective COX-2 inhibitors (Celecoxib, Etoricoxib) spare the stomach but increase cardiovascular thrombotic risk (stroke/MI) due to endothelial PGI2 inhibition without platelet TXA2 suppression. Naproxen carries the lowest relative CV risk.

• Aspirin Special Note: Irreversibly acetylates COX-1 in platelets for their entire 7–10 day lifespan. Contraindicated in children with viral infections due to Reye’s syndrome.

Step 2 Weak Opioids (Codeine & Tramadol)

• Codeine: Codeine is a prodrug metabolized to morphine via hepatic CYP2D6. Approximately 6–10% of Caucasians are poor metabolizers (lack analgesia), whereas ultra-rapid metabolizers experience severe opioid toxicity or fatal neonatal respiratory depression in nursing mothers.
• Compound Preparations: Co-codamol 30/500 (30 mg codeine / 500 mg paracetamol) provides synergistic analgesia. Low-dose preparations (8/500) are sub-therapeutic for cancer pain.
• Tramadol Dual Mechanism: Weak mu-opioid receptor agonist (via active M1 metabolite) PLUS inhibition of serotonin and norepinephrine reuptake in the spinal cord. Lowers seizure threshold and risks serotonin syndrome with SSRIs/MAOIs.

Step 3 Strong Opioids (Morphine Titration Protocol)

• No Ceiling Effect: Strong opioids have no upper efficacy plateau; dosage is titrated against pain relief vs adverse side effects.
• Morphine Titration Rules
  1. Opioid-Naive Patients: Start immediate-release (IR) oral morphine 2.5–5 mg every 4 hours + PRN breakthrough doses.
  2. Daily Recalculation: After 24–48 hours, sum total 24-hour regular + PRN requirements. Divide by 6 to set new 4-hourly dose.
  4. Breakthrough PRN Dose: Prescribe 50–100% of the single 4-hourly dose (or 1/6th of total daily dose) as IR morphine PRN.
• Renal Impairment Caution: Morphine glucuronides (M6G – analgesic; M3G – neurotoxic/myoclonus) accumulate in renal impairment. Hydromorphone, Fentanyl, or Buprenorphine are preferred in renal failure.

Advantages & Modern Limitations of the Ladder

  • Advantages: Provides a simple, structured, international standard for non-specialists; ensures rational drug escalation; integrates adjuvant therapies.
  • Limitations: Strict linear progression may delay effective pain relief in severe acute or malignant pain where skipping Step 2 directly to low-dose Step 3 opioids is clinically preferred; lacks guidance on non-pharmacological modalities.

CLINICAL GUIDELINE SUMMARY: WHO & EAPC Clinical Guidelines for Cancer Pain Relief
World Health Organization (WHO) and European Association for Palliative Care (EAPC) guidelines state that for patients presenting with moderate-to-severe cancer pain, direct initiation of low-dose Step 3 strong opioids (e.g., low-dose oral morphine or transdermal buprenorphine) is superior in efficacy and tolerability compared to traditional Step 2 weak opioids.


Standard References

Cherny NI, Fallon M, Kaasa S, Portenoy RK, Currow DC, eds. Oxford Textbook of Palliative Medicine. 6th ed. Oxford University Press; 2021.

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