Ondansetron

Question 1

Drug class

Answer 1

Anti-emetic

Question 2

Pharmacology

Answer 2

Is a serotonin 5-HT3 receptor antagonist that primarily reduces the activity of the vagus nerve, which actives the vomiting center in the medulla oblongata, and also blocks serotonin receptors in the chemoreceptor trigger zone

Question 3

Metabolism

Answer 3

Majority by the liver & excreted by the kidneys

Question 4

Indications

Answer 4

Significant nausea and/or vomiting

Question 5

Contraindications

Answer 5

• Allergy and/or adverse drug reaction
• Congenital long QT syndrome
• Current apomorphine therapy (dopamine agonist used in the rx of parkinsonism)
• Pts <2yrs

Question 6

Precautions

Answer 6

• Hepatic impairment
• Intestinal obstruction
• Pts with risk factors for QT interval prolongation or cardiac arrhythmias
• First trimester pregnancy (extreme & uncontrolled hyperemesis)

Question 7

Adverse events

Answer 7

Common
• Headache
• Constipation
Rare 
• Hypersensitivity reactions 
• ECG changes

Question 8

Presentation

Answer 8

• 4mg/2ml amp

* 4mg Orally disintegrating tablet (ODT)

Question 9

Routes

Onset

Duration

Answer 9

PO / IM / IV

IV O: 5mins

IV D: Several hours

Question 10

Adult dosages

Answer 10

PO / IM / IV
4-8mg, total max dose 8mg
*IV slow push over 2-3min

Question 11

Paediatric dosages

Answer 11

PO
≥5yrs 4mg, single dose only
2-4yrs 2mg, single dose only

IM
≥2yrs 100mcg/kg (rounded to nearest 5kg)
Single dose only, not to exceed 4mg

Weight/Dose/Volume
> 15-20kg / 2mg / 1ml
> 20-25kg / 2.5mg / 1.25ml
> 25-30kg / 3mg / 1.5ml
> 30-35kg / 3.5mg / 1.75ml
> 35kg / 4mg / 2ml

IV
≥2yrs 100mcg/kg, slow push over 2-3min, single dose only, not to exceed 4mg