Published: May 2009

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The cough and cold season is on its way - caution for patients receiving SSRIs

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Prescriber Update 30(2): 13
May 2009

Prescribers are reminded of the potential interaction between selective serotonin reuptake inhibitors (SSRI) and dextromethorphan, commonly included in cough and cold products. CARM has received a report of a patient taking citalopram who experienced a serotonin syndrome-type reaction following the use of an over the counter medicine containing dextromethorphan.

Serotonin syndrome is a dose-dependent toxic state caused by excess serotonin within the CNS and is characterised by mental, autonomic and neuromuscular changes. Clinical features include confusion, agitation, hyperactivity sweating, tachycardia, ataxia, hypertonia and tremor.

The mechanism for this interaction is not fully understood; however it has been suggested that the reaction may be due to the additive effects of SSRIs and dextromethorphan on serotonin transmission. SSRIs are known to inhibit cytochrome P450 isoenzyme CYP2D6, the same enzyme which catalyses dextromethorphan metabolism.¹

Patients should be informed about this potentially serious drug interaction and advised to check with their pharmacist when purchasing cough and cold medicines. Pharmacists are reminded to ask about concomitant medicines when recommending cough and cold products.

Reference

1. SSRIs and related antidepressants. In Stockley IH (Ed) Stockley's Drug Interactions Electronic version, 2009.