Published: 2 September 2015


Reminder: Interactions Resulting in Serotonin Syndrome

Prescriber Update 36(3): 35
September 2015

Key Messages

  • Serotonin syndrome can result from a pharmacodynamic interaction between medicines with serotonergic effects.
  • Medicines with serotonergic effects also include medicines other than antidepressants such as tramadol, methylene blue and linezolid.
  • Healthcare professionals are reminded that patients taking more than one serotonergic medicine are at an increased risk of developing serotonin syndrome.

Healthcare professionals are reminded that the risk of developing serotonin syndrome is increased in patients taking more than one serotonergic medicine.

The Centre for Adverse Reactions Monitoring (CARM) has recently received two reports of patients taking regular fluoxetine who developed serotonin syndrome after tramadol was started. The symptoms improved after tramadol was stopped.

Although tramadol is an analgesic, it also has serotonergic effects and should be avoided in patients taking serotonin reuptake inhibitors.

Pharmacodynamic interactions include interactions that occur between medicines which have similar pharmacological effects or adverse effects1. Serotonin syndrome is an example of a pharmacodynamic interaction where two or more medicines with serotonergic effects interact resulting in serotonin toxicity.

Further information on serotonin syndrome, including a summary table of serotonergic medicines, can be found in a previous edition of Prescriber Update2.

Healthcare professionals are encouraged to report all suspicions of medicine interactions to CARM. Reports may be submitted on paper or electronically (

  1. New Zealand Formulary. 2015. Drug interactions. NZF v37. URL: (accessed 14 July 2015).
  2. Medsafe. 2010. Serotonin syndrome/toxicity — reminder. Prescriber Update 31(4): 30–31. URL: (accessed 14 July 2015).
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