Ondansetron and prolonged QT on 12 lead

asked 2 months ago

This is a 2 part question:

One of the contraindications of ondansetron is "prolonged QT syndrome (known to patient)". If a 12 lead is performed before administering an antiemetic (i.e. in an elderly pt with acute onset of nausea/vomiting/chest pain) and a prolonged QTc is found, should ondansetron be withheld?
If ondansetron has to be withheld, if it's contraindicated, or if the primary cause of the nausea/vomiting is vertigo, can dimenhydrinate be administered to > 65-year-old patients? The directive only says it can be administered to that patient population when "ondansetron is unavailable."

1 Answers

answered 2 months ago

Thank you for your questions.

Yes, I would withhold ondansetron if prolonged QT is noticed on ECG. This does not mean you need to perform an ECG prior to ondansetron administration but if you do for other reasons, I would not ignore it.
As you have indicated, dimenhydrinate is a better choice when vertigo is the cause of nausea. In these cases, a patch to the BHP would be in order. Provincially, we are reviewing all of the medical directives and the use of dimenhydrinate for vertigo has been discussed as a possible change.