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Side-Effects of Opioids

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Constipation, sedation, dizziness, nausea and vomiting are the most common side-effects. However, in general, most of these are short-lived, except for constipation.

Portenoy ([i]), in his 1996 paper

"Opioid therapy for chronic non-malignant pain: A review of the critical issues", wrote:

"Long-term opioid therapy has not been associated with major organ toxicity in large surveys of cancer patients or patients maintained on methadone. Although constipation is the only persistent side-effect that occurs, some patients experience other adverse effects such as somnolence, confusion or nausea. Cognitive impairment is also possible, as well as subtle changes in reaction time."

Hendler et al ([ii].) found that patients on narcotics scored the same on cognitive testing as patients on no medications. Indeed, some authors believe that opioids, by virtue of providing adequate pain relief, may in fact improve cognitive function that was previously impaired by a high pain level.

Side-effects include:

  • Constipation
  • Decreased libido
  • Depression
  • Oedema (fluid retention)
  • Headache
  • Insomnia
  • Itching/skin rash
  • Nausea and vomiting
  • Sedation
  • Withdrawal syndrome

Further details on dealing with these problems may be found later in this article.

[i] Portenoy  RK J Pain Symptom Manage 1996 11(4):203-217 Opioid therapy for chronic nonmalignant pain: A review of the critical issues.


[ii] Hendler N, Cimini C, Ma T, Long D. Am J Psychiatry 1980 A comparison of cognitive impairment due to benzodiazepines and to narcotics