Serotonin-blocking medicines used to treat nausea and vomiting

Consumers and health professionals are advised that serotonin syndrome is a newly identified issue associated with products containing the serotonin-blocking medicines classed as 5-HT3 receptor antagonists.

These medicines are used after surgery and in patients undergoing cancer treatment to prevent nausea and vomiting. They work by blocking serotonin from entering certain cells in the nervous system and brain.

Serotonin syndrome has been seen in patients using 5-HT3 receptor antagonists at the same time as otherserotonergic medicines. The 5-HT3 receptor antagonists available in Australia are: granisetron (Sancuso and Kytril), dolasetron (Anzemet), tropisetron (Navoban), ondansetron (Zofran) and palonosetron (Aloxi).

Serotonin syndrome occurs when serotonin accumulates to high levels in the body, as can happen when medicines block the chemical from entering cells. The syndrome is characterised by:

• altered mental state, e.g. confusion, agitation, restlessness and excitement
• autonomic dysfunction, e.g. tachycardia, sweating, shivering, hypertension and hyperthermia
• neuromuscular excitation, e.g. hyperreflexia, tremor.

In some cases serotonin syndrome can lead to loss of consciousness, coma and death.

Health Canada published safety information about this issue after completing a review of 5-HT3 receptor antagonists.

The TGA has previously published an article regarding serotonin syndrome, including information about diagnosis and treatment of this potentially life-threatening condition.

Information for consumers

If you, or someone you care for, is being treated for nausea and vomiting with a serotonin-blocking medicine and experiences the symptoms listed above, contact a health practitioner immediately.

If you have any questions or concerns about this issue, please contact your treating doctor.

Information for health professionals

Health professionals are advised to be alert to this issue.

The TGA is working with the sponsors of the different 5-HT3 receptor antagonists to update their Product Information (PI) regarding the risk of serotonin syndrome. Some sponsors already include this information in their PI.

The updated PI contains a new precaution and information on drug interactions advising that serotonin syndrome has been described following the use of 5-HT3 receptor antagonists when used concomitantly with other serotonergic drugs, including selective serotonin reuptake inhibitors (SSRIs) and serotonin noradrenaline reuptake inhibitors (SNRIs).

If concomitant treatment with a 5-HT3 receptor antagonist and other serotonergic drugs is clinically warranted, it is advised that the patient and caregivers are advised of this issue and that appropriate observation is undertaken.

Reporting problems

Consumers and health professionals are encouraged to report problems with medicines or vaccines. Your report will contribute to the TGA’s monitoring of these products.

The TGA cannot give advice about an individual’s medical condition. You are strongly encouraged to talk with a health professional if you are concerned about a possible adverse event associated with a medicine or vaccine.

(Source: Australian Government – Department of Health)