Serotonin syndrome

Serotonin is derived from amino acid tryptophan and is naturally occurring in the body. In the central nervous system it acts as a neurotransmitter and can influence mood, sleep, appetite and various other brain functions.

Excess serotonin in the central nervous system is referred to as serotonin syndrome or serotonin toxicity, and can be caused by various drug mechanisms. The symptoms may include: clonus, hyperreflexia, myoclonus, muscle rigidity, hyperthermia, tachycardia, diaphoresis, tremor, flushing, anxiety, agitation or confusion.

Some drugs that have been associated with serotonin syndrome:

 Serotonin reuptake inhibitors o Selective serotonin reuptake inhibitors (SSRIs) antidepressants o Other antidepressants, including tricyclic antidepressants o Opiod analgesics, including pethidine, tramadol  Monoamineoxidase inhibitors (MAOIs)  Serotonin releasers o Amphetamines, ecstasy  Some migraine medications including sumatriptan, dihydroergotamine  Miscellaneous o Lithium o Tryptophan  Herbal medications e.g. St John’s wort

Serotonin syndrome can occur with single drug treatment, but more commonly with drug combination and/or misuse, or drug overdose.

Serotonin syndrome coding guidelines Coding of serotonin syndrome will depend on whether there was proper or improper drug use. If the syndrome is caused by an adverse effect of correct substance(s) properly administered, follow ACS 1902 Adverse effects and assign codes for the symptom(s) followed by adverse effect codes. Separate external cause codes are required for each different drug type.

Coding Education Team Performance Activity & Quality Division Department of Health WA Last reviewed May 2013

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If the syndrome results from improper use such as overdose, or prescribed drugs taken in combination with self-prescribed drugs and/or intoxication, follow ACS 1901 Poisoning and assign a code from T36-T50, followed by the symptom(s) and external cause codes. Separate poisoning and external cause codes are required for each different drug type.

If there is no documentation of the drug(s) resulting in serotonin syndrome, clarification should be sought from the clinician. If this is not possible, code the symptom(s) as an adverse effect of an antidepressant NEC.

References: Ibister, G, Buckley, N, Whyte, I. Serotonin toxicity: a practical approach to diagnosis and treatment. MJA [serial on the Internet]. 2007 Jun 25; [cited 2011 March 29]; 187 (6): [4 pages]. Available from: http://www.mja.com.au/public/issues/187_06_170907/isb10375_fm.html

Hill, M. Serotonin syndrome. Australian Prescriber [serial on the Internet]. 2003 Jun; [cited 2011 March 29]; 26: [2 pages]. Available from: http://www.australianprescriber.com/magazine/26/3/62/3/

Coding Education Team Performance Activity & Quality Division Department of Health WA Last reviewed May 2013

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