Purpose and principles
Use the WHO cancer-pain framework as a flexible guide, combine mechanism-specific medicines with disease treatment, rehabilitation and psychosocial care, and avoid reflex opioid escalation when a different modality offers greater benefit.
The three-step WHO framework remains a useful organising concept for cancer pain but is not a compulsory staircase. Step one uses non-opioid analgesia with or without an adjuvant. Step two traditionally adds a weak opioid such as codeine. Step three uses a strong opioid for moderate-to-severe pain. At every step, assess mechanism, treat reversible pathology, provide rescue for predictable flares and monitor function and toxicity.
Weak opioids have limitations. Codeine depends on CYP2D6 conversion to morphine, giving variable analgesia and toxicity, and its metabolites accumulate in renal impairment. Combining it with paracetamol creates a ceiling imposed by the non-opioid component. In severe progressive pain, a lower carefully titrated dose of strong opioid can be more controllable than maximising a weak opioid, provided the patient receives education, constipation prophylaxis and close review.