Ondansetron
- Class: 5-HT3 antagonist
- Used for: nausea
- Say it: on-DAN-seh-tron
- Forms: tablet, dissolving tablet, oral liquid, injection
Remember the name – ON-DANSE → dance
ONDANSETRON stops the stomach's DANCE. The churning settles and the nausea goes with it.
Blocking 5-HT3 receptors in the gut and the vomiting centre stops the signal that starts the dance — which is why it works so well for chemotherapy sickness.
ONDANSETRON stops the stomach's DANCE. The churning settles and the nausea goes with it.
Blocking 5-HT3 receptors in the gut and the vomiting centre stops the signal that starts the dance — which is why it works so well for chemotherapy sickness.
Mnemonic: A -SETRON silences the serotonin alarm
The -setron drugs block 5-HT3. Chemotherapy and anaesthesia flood the gut with serotonin, which is exactly why ondansetron shines for those two causes.
The -setron drugs block 5-HT3. Chemotherapy and anaesthesia flood the gut with serotonin, which is exactly why ondansetron shines for those two causes.
Side effects
Common: headache, constipation, dizziness
Serious: QT prolongation, serotonin syndrome
Typical dose
4–8 mg two or three times daily
Causes constipation and prolongs the QT interval.
Check yourself
Ondansetron works best for nausea caused by...
- chemotherapy or anaesthesia, where serotonin pours out of the gut
- motion sickness, which runs on histamine and acetylcholine
- an inner-ear problem causing vertigo
- any cause — it works equally well for all of them
Show answer
A. chemotherapy or anaesthesia, where serotonin pours out of the gut
Matching the antiemetic to the pathway is the whole skill. Motion sickness and vertigo travel by histaminergic and cholinergic routes, so a 5-HT3 blocker does comparatively little for them.
See it, don't memorize it
The app has the mechanism comic and a patient case for Ondansetron – plus the name link, the class mnemonic, pronunciation you can hear, and a self-check, for the top 100 drugs. One purchase, no subscription, no account.