Ondansetron

Question 1

Pharmacology and presentation of Ondansetron?

Answer 1

4mg Orally Disintegrating Tablet or 8mg/4ml Ampoule

Ondansetron is a serotonin 5-HT3 receptor antagonist used primarily as an antiemetic. Ondansetron reduces the activity of the vagus nerve, which activates the vomiting centre in the medulla oblongata, and also blocks serotonin receptors in the chemoreceptor trigger zone.

Question 2

Indicators of Ondansetron?
- MNS

Answer 2

• Nausea and vomiting
• Motion sickness secondary to road or aeromedical transport
• Suspected spinal injury.

Question 3

Contraindications of Ondansetron?
- Ondans Dance with new hand waves

Answer 3

• Known allergy
• Congenital long QT syndrome
• Hypokalaemia or hypomagnesaemia
• Current Apomorphine therapy
• Age <3 years.

Question 4

Cautions of Ondansetron?
- HIP PT

Answer 4

• Hepatic impairment
• Patients at risk of QT prolongation or cardiac arrhythmias
• Intestinal obstruction
• Pregnancy
• Current Tramadol therapy.

Question 5

Side Effects of Ondansetron?

• CD Prolonged Serotonin Headache

Answer 5

• Constipation
• Headache
• Dizziness
• QT prolongation and sequelae
• Serotonergic syndrome in combination with other serotonergic drugs

Question 6

Dosing Regimes of Ondansetron?

Answer 6

SL/PO
- Adults = 4mg ODT SL/PO, repeat once after 5 mins to a max of 8mg
- Paeds 3-5years = 2mg ODT PO or >5year = 4mg ODT PO, single dose

IM/IV
- Adults = 4-8mg IM or IV (pushed over 30secs IV or administered in both deltoids IM) to a max of 8mg

Question 7

Onset and duration of Ondansetron?

Answer 7

• Onset = 5 minutes
• Duration = Several hours