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Side effects


  • adverse effects
  • side reaction


An unwanted effect caused by a drug or therapy. Such effects can be drug related, dose related, route related, patient related, caused by an interaction with another drug, or caused by opioid initiation or dose escalation.

Definition from: NCI Thesaurus via Unified Medical Language SystemThis link leads to a site outside Genetics Home Reference. at the National Library of Medicine

A secondary and usually adverse effect (as of a drug) <toxic side effects> <a side effect of drowsiness caused by antihistamines> -- called also side reaction.

Definition from: Merriam-Webster's Medical DictionaryThis link leads to a site outside Genetics Home Reference. by Merriam-Webster Inc.

Related discussion in the Handbook

See also Understanding Medical Terminology.

Published: February 8, 2016