Cancer Pain and Palliative Care: The WHO Ladder and Beyond
Cancer pain is rarely conquered by one heroic drug. It is layered — a steady background opioid, a top-up for breakthrough, an adjuvant tuned to the nerve or bone, and, never forgotten, a laxative to keep the bowel moving. This is the discipline of the WHO analgesic ladder and the humane logic of palliative care: relieve suffering, in proportion, by the mouth, by the clock, by the ladder.
A 64-year-old woman with breast cancer that has spread to her spine describes a deep, gnawing ache that never fully sleeps, punctured by lightning jolts down one leg when she moves. One doctor reaches for a single, ever-stronger painkiller and keeps raising it; her pain still breaks through, and now she is drowsy and constipated to the point of misery. A second team builds a plan instead of a dose: a regular background morphine to smooth the baseline, an immediate-release top-up for the flares, a nerve-pain adjuvant for the electric leg, and — written on the very first prescription — a laxative. Within days she is comfortable and clear-headed. The lesson of this article is that quiet plan: cancer pain is controlled by layers, not by heroics.
The WHO analgesic ladder
The whole approach fits on three steps. The World Health Organization (WHO) analgesic ladder matches the strength of the drug to the severity of the pain. Step 1 (mild pain): a non-opioid — paracetamol (acetaminophen) or a non-steroidal anti-inflammatory drug (NSAID) — with or without an adjuvant. Step 2 (mild-to-moderate pain): add a weak opioid such as codeine or tramadol, still with the non-opioid and any adjuvant. Step 3 (moderate-to-severe pain): swap in a STRONG opioid — morphine, oxycodone, a fentanyl patch, or hydromorphone — again layered on the non-opioid and adjuvant as needed. You climb the ladder if pain persists and titrate the dose to the pain itself.
The WHO ladder travels with three companion rules: "by the mouth" (use the oral route whenever possible — it is simple and preserves independence), "by the clock" (give regular doses on a fixed schedule, not only when pain returns), and "by the ladder" (step up in strength to match severity). These three phrases carry more clinical wisdom than any single drug name.
Note that an adjuvant — a drug not primarily an analgesic but useful for a specific pain, such as gabapentin for nerve pain or dexamethasone for a compressed nerve — can be added at ANY step, not just at the top. A patient on Step 1 paracetamol may still need amitriptyline for a neuropathic component from day one. The ladder is about opioid strength; adjuvants run alongside it throughout.
- Step 1 = non-opioid (paracetamol / NSAID) ± adjuvant, for mild pain.
- Step 2 = weak opioid (codeine, tramadol) added on, for mild-moderate pain.
- Step 3 = strong opioid (morphine, oxycodone, fentanyl, hydromorphone) for severe pain.
- "By the mouth, by the clock, by the ladder" — the three governing principles.
- Adjuvants can be added at any step, not reserved for the top.
- Titrate to the pain — the right dose is the one that relieves it safely.
Opioid principles in cancer: background plus breakthrough
Once you reach strong opioids, the shape of dosing matters as much as the drug. Cancer pain has two faces: a constant baseline and sudden flares. So you give two doses in tandem. A regular BACKGROUND dose, usually a modified-release (slow-release) opioid taken on a fixed schedule, smooths the baseline. A BREAKTHROUGH dose, an immediate-release form taken as needed for flares, covers the spikes. The breakthrough dose is classically about one-sixth (1/6) of the total daily background dose. If a patient needs many breakthrough doses a day, that is the signal to raise the background dose — you recalculate rather than leave them chasing the pain.
Pure opioid agonists have no ceiling. Unlike a non-opioid such as paracetamol — which has a maximum daily dose beyond which you only add toxicity, not analgesia — a pure opioid agonist (morphine, oxycodone, hydromorphone, fentanyl) has NO analgesic ceiling. The correct dose is whatever controls the pain while side effects stay tolerable. That is why titration is central: you climb the dose against the pain, guided by response and by sedation, not by a printed maximum. This principle underpins the opioid pharmacology covered in the central nervous system (CNS) section, where receptor action, tolerance, and reversal with naloxone are detailed.
When you rotate from one opioid to another — say a patient on oral morphine develops intolerable nausea and you move to oxycodone, or you switch a stable patient to a fentanyl patch — you convert doses using published equianalgesic ratios (equivalence tables). Because of incomplete cross-tolerance, the calculated equivalent dose is usually reduced by roughly a quarter to a third when starting the new drug, then re-titrated. Getting the ratio wrong in either direction is a real source of harm, so opioid conversion is done carefully and, where possible, with specialist input.
Managing the predictable side effects
Strong opioids come with side effects that are so predictable you plan for them before they appear. Constipation is near-universal: opioids slow the gut, and — crucially — tolerance does NOT develop to this effect the way it does to nausea or sedation. So a laxative is co-prescribed from the start and continued for as long as the opioid is taken; it is not an optional extra. Nausea is common but usually transient in the first days, and an antiemetic can cover that window. Sedation and, at the dangerous end, respiratory depression are dose-related; sedation often eases as tolerance builds, but excessive drowsiness is a warning sign, and naloxone reverses a genuine opioid overdose. The laxative story connects to the gastrointestinal (GI) section, and the naloxone/tolerance story to the CNS section.
Transdermal fentanyl and buprenorphine patches suit two situations well: stable, steady pain (a patch gives smooth levels over days and is convenient for someone who struggles to swallow), and renal impairment. Morphine's active metabolites are cleared by the kidney and accumulate in renal failure, causing sedation and twitching; fentanyl and buprenorphine lack clinically significant active metabolites and are safer choices there. Patches are for BACKGROUND pain, though — their slow onset makes them unsuitable for rapid titration in a pain crisis.
- Give a regular modified-release background dose PLUS immediate-release breakthrough.
- Breakthrough dose ≈ 1/6 of the total daily background dose.
- Pure opioid agonists have no analgesic ceiling — titrate to effect.
- Always co-prescribe a laxative; tolerance to constipation does NOT develop.
- Nausea is usually transient; sedation/respiratory depression are dose-related (naloxone reverses overdose).
- Use fentanyl/buprenorphine patches in renal impairment or stable pain, not for a crisis.
Adjuvants: matching the drug to the kind of pain
Not all pain answers to opioids equally. Two cancer pains especially need adjuvants layered on. NEUROPATHIC pain — the burning, shooting, electric pain of a nerve infiltrated or compressed by tumour — responds best to gabapentinoids (gabapentin, pregabalin), the tricyclic antidepressant amitriptyline, or the serotonin-noradrenaline reuptake inhibitor duloxetine. BONE pain — the aching pain of skeletal metastases — is often helped by NSAIDs, by bone-targeted agents (bisphosphonates such as zoledronic acid, or denosumab), by radiotherapy to a painful deposit, and by dexamethasone where a nerve is being compressed or intracranial pressure is raised. These neuropathic adjuvants are the same drugs detailed in the CNS and Inflammation sections; the bisphosphonates connect to the Endocrine bone chapter.
Steroids earn a special mention. Dexamethasone reduces the swelling around a tumour, and that single action relieves several distinct emergencies: pain from a nerve compressed by oedema, the headache of raised intracranial pressure, and the pain of spinal cord compression (where high-dose dexamethasone plus urgent radiotherapy or surgery is the classic response). One drug, several palliative uses — but its own side-effect burden means it is used deliberately, not casually.
Palliative and end-of-life symptom control
Palliative care is far wider than pain. As disease advances, a cluster of symptoms recurs and each has an answer. Nausea and vomiting are matched to their cause with the appropriate antiemetic. Breathlessness — one of the most frightening symptoms — is eased by a low-dose opioid, which blunts the sensation of air hunger, alongside simple measures such as a fan and positioning. Noisy respiratory secretions in the final hours (the sound distresses families more than the patient) are dried by anticholinergic drugs such as hyoscine (scopolamine) or glycopyrronium. Terminal agitation or restlessness is settled with sedating agents. The aim throughout is comfort.
One ethical principle guides the doses. Underlying all of this is the principle of PROPORTIONATE symptom relief: you give the dose needed to relieve the suffering in front of you, no more and no less, with the intention of easing symptoms — not of ending life. When an opioid or sedative is titrated carefully against a distressing symptom, any incidental shortening of life that some fear is neither the goal nor, in practice, a common consequence; good symptom control does not equate to hastening death. This is the moral backbone of palliative prescribing: relieve in proportion, with honest intent, and keep the patient comfortable and, wherever possible, lucid.
- Neuropathic pain → gabapentinoids, amitriptyline, or duloxetine.
- Bone pain → NSAIDs, bisphosphonates/denosumab, radiotherapy, ± dexamethasone.
- Dexamethasone relieves oedema-related pain, raised ICP, and cord compression.
- Breathlessness responds to a low-dose opioid; secretions to anticholinergics.
- Proportionate relief: dose to ease suffering, with the intention of comfort.
- Prescribing a strong opioid without a regular laxative. Constipation is near-universal and does not wane with tolerance — the laxative is not optional.
- Dosing only "as needed" and waiting for pain to return, instead of giving regular doses "by the clock".
- Using morphine unadjusted in renal failure — active metabolites accumulate; prefer fentanyl or oxycodone.
- Forgetting adjuvants — climbing opioid doses for neuropathic or bone pain that would answer better to gabapentinoids, an NSAID, or radiotherapy.
A patient is started on a modified-release oral morphine for severe bone-metastasis pain. Which co-prescription should accompany it from the very first prescription?
- The WHO ladder: Step 1 non-opioid, Step 2 weak opioid, Step 3 strong opioid — ± adjuvant, titrated "by the mouth, by the clock, by the ladder."
- Give a modified-release background dose plus immediate-release breakthrough (~1/6 of the daily dose); pure agonists have no ceiling.
- Always co-prescribe a laxative; manage nausea/sedation; use fentanyl/oxycodone (not morphine) in renal failure.
- Match adjuvants to the pain: gabapentinoids/TCA/duloxetine for neuropathic, NSAIDs/bisphosphonates/radiotherapy/steroids for bone.
- Palliative care controls nausea, breathlessness, secretions and agitation under the principle of proportionate relief.
- World Health Organization. WHO Guidelines for the Pharmacological and Radiotherapeutic Management of Cancer Pain in Adults and Adolescents.
- World Health Organization. Cancer Pain Relief (the analgesic ladder) — "by the mouth, by the clock, by the ladder."
- Twycross R, Wilcock A, Howard P. Palliative Care Formulary (PCF) — opioid titration, breakthrough dosing & symptom control.
- Rang HP, Dale MM, et al. Rang & Dale's Pharmacology — opioid analgesics, tolerance, dependence & naloxone.
- Brunton LL, et al. Goodman & Gilman's The Pharmacological Basis of Therapeutics — opioid analgesics & adjuvant analgesics.
- National Institute for Health and Care Excellence (NICE). Palliative care for adults: strong opioids for pain relief (NG / CG guidance).
- European Association for Palliative Care (EAPC). Use of opioid analgesics in the treatment of cancer pain: evidence-based recommendations.
