A patient commencing regular oral morphine for cancer pain asks about expected side effects. Which statement is CORRECT regarding tolerance to opioid adverse effects?

• A Tolerance develops to nausea but not to constipation ✓
• B Tolerance develops to constipation within one to two weeks
• C Tolerance develops equally to all gastrointestinal effects
• D No tolerance develops to any opioid adverse effect

Explanation

Tolerance develops rapidly to respiratory depression, sedation, nausea and vomiting, usually within days to weeks, but no clinically significant tolerance develops to constipation or miosis. B laxative must therefore be prescribed alongside every regular opioid throughout treatment. This asymmetry explains why nausea often settles spontaneously while constipation persists indefinitely, and it kills the distractors claiming uniform tolerance or universal absence of tolerance across all opioid adverse effects.

Reference: Oxford Textbook of Palliative Medicine, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.