Side effect can mean:

  • Adverse drug reaction, an unintended consequence specifically arising from drug therapy
  • Therapeutic effect, a desirable consequence of any kind of medical treatment, even though resulting as an unintended, unexpected consequence of the treatment
  • Adverse effect (medicine), an unintended, and undesirable, consequence of any kind of medical treatment
  • Unintended consequence, an effect that is unforeseen, regardless of type or quality

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