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Side effects of opioids (strong and weak)

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

Authoring team

  • constipation
    • must be anticipated and prevented in all patients on weak or strong opioids. Regular stimulant laxatives must be commenced at the same time as weak or strong opioids. The dose of laxative should increase as the dose of opioid increases
    • constipation may be less severe in some patients with transdermal fentanyl.
  • sedation
    • may occur with the first few doses, but then lessens
  • nausea
    • is a common problem during the first few days of treatment. If it occurs, haloperidol, domperidone, cyclizine or metoclopramide are useful
  • also recognised
    • dry mouth, itching, sweating, hallucinations and myoclonic jerks
  • psychological addiction
    • does not occur in patients taking opioids for their analgesic effects
  • tolerance
    • may occasionally occur, but an increase in dose requirement usually reflects an increase in pain due to advancing disease. Some patients may exhibit tolerance or intolerance (excessive side effects), to a particular strong opioid and switching to another strong opioid might be helpful. Seek specialist advice
  • respiratory depression
    • is not a risk when doses are increased by appropriate amounts
    • if pain is relieved by alternative methods e.g. radiotherapy or nerve block, a reduction in opioid dose will be required


  1. West Midlands Palliative Care Physicians (2007). Palliative care - guidelines for the use of drugs in symptom control.
  2. St Elizabeth Hospice Guidelines, Ipswich, 1997.

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