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Fentanyl patches: risk of fatal overdose

Fentanyl is a powerful analgesic. Due to the risk of overdose, precautions must be taken in using and disposing of fentanyl patches.

Fentanyl is a powerful analgesic that can be used in some cases of intense, chronic, stable pain. It contains morphine and has similar adverse effects: gastrointestinal, neuropsychological and urinary disorders. When presented in transdermal patches, it carries specific risk of overdose. A patch removed after 72 hours still contains significant quantities of fentanyl.

The symptoms of overdose include respiratory depression and hypotension, convulsions, and sometimes muscle wasting and pulmonary oedema. Several cases of fatal overdose have been reported, including in France.

Overdoses are generally the result of a poor understanding of the use of the patch or incorrect handling, confusion between 2 dosages, forgetting to remove the patch, unwitting transfer to another person, multiple applications, cutting up the patch, self-medication or swallowing the patch, etc.

Raised skin temperature (due to fever, an electric blanket or intense physical exercise) boosts fentanyl absorption and exposes the patient to the risk of overdose.

Precautions should be taken when applying and changing the patch, and any signs of overdose should be monitored so as to permit action to be taken without delay. Instructions for use and disposal should be strictly adhered to.

©Prescrire February 2010

"Fentanyl patches: preventable overdose" Prescrire Int 2010; 19 (105): 22-25 (pdf, subscribers only).

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