Why Does Ondancestron Cause Qt Problems At Very High Doses

[biggirlkisss]

why does ondancestron cause qt problems at very high doses? Why would it do that?

 

[Blossom]

From openanesthesia.org:

The QRS widening is likely due to blockade of sodium channels while the QT prolongation is caused by blocking potassium channels.

 

[Blossom]

Here is the whole paragraph:

5HT-3 antagonists

Known to cause QT prolongation, ex. ondansetron (Zofran), granisetron (Kytril), and dolasetron (Anzemet). These drugs have been reported to widen the QRS complex and prolong JT, QT, and PR intervals. Dolasetron (1.2-4mg/kg IV) can prolong QRS by 5-20% whereas Ondansetron has been shown to increase QT and JT intervals by an average of 2-5%. The QRS widening is likely due to blockade of sodium channels while the QT prolongation is caused by blocking potassium channels. In a study done with human myocytes, all of the drugs in this class where shown to block human cardiac Na+ channels probably by interacting with the inactivated state. This could lead to clinically relevant blockade, especially with high heart rates or depolarized/ischemic tissue, potentially leading to ventricular arrhythmias. The rank order of potency for Na+ blockade is granisetron>dolasetron>ondansetron. For blockade of the K+ channel (QT prolongation), the order of potency is ondansetron>granisetron>dolasetron.

https://www.openanesthesia.org/

 

[DaveFoster]

Most antidepressants prolong the QT interval.

 

[ddjd]

why does ondancestron cause qt problems at very high doses? Why would it do that?

What do you mean by QT

 

[biggirlkisss]

joeyd heart problems... Umm would increasing sodium and potassium counter the qt problems?

 

[Blossom]

joeyd heart problems... Umm would increasing sodium and potassium counter the qt problems?

The QT interval has to do with the electrical activity in the heart muscle and is the time between the Q wave and the T wave on a persons ECG. The fix will depend on the cause. If it's medication induced then adjusting or discontinuing the medication may be necessary. If it's low blood potassium or magnesium then that would need to be corrected. If it's from a thyroid issue that would need treatment etc. The following link has more information that may be relevant.
Long QT Syndrome | NHLBI, NIH

 

[Tarmander]

The QT interval has to do with the electrical activity in the heart muscle and is the time between the Q wave and the T wave on a persons ECG. The fix will depend on the cause. If it's medication induced then adjusting or discontinuing the medication may be necessary. If it's low blood potassium or magnesium then that would need to be corrected. If it's from a thyroid issue that would need treatment etc. The following link has more information that may be relevant.
Long QT Syndrome | NHLBI, NIH

Nice to see you back around Blossom

 

[Blossom]

Nice to see you back around Blossom

Thanks Tarmander!