Ondansetron

Question 1

Presentation

Answer 1

1. 4mg ODT

2. 8mg in 4ml

Question 2

Indications

Answer 2

1. Undifferentiated nausea and vomiting
2. Vestibular nausea <21years
3. Prophylactic ally for spinal immobilisation and penetrating eye injuries

Question 3

Contraindications

Answer 3

1. Hypersensitivity
2. Long QT syndrome
3. Hypomagnesia or hypokalaemia
4. Concurrent apomorphine use

Question 4

Precautions

Answer 4

1. Patients with liver disease should have no more than 8mg per day
2. Concurrent use of transfix
3. Care should be taken with patients on diuretics due to ? Electrolyte imbalances
4. Patients with phenyleketonuria due to Indians containing aspartame

Question 5

Side effects

Answer 5

Common
1. Constipation 
2. Headache 
3. Fever 
4. Dizziness 
4. Rise in liver enzymes 
Rare 
1. Extrapyramidal reactions 
2. Hypersensitivity reactions 
3. Widened QRS
4. QT prolongation 
5. Tachyarrhythmias 
6. Seizures 
7. Visual disturbances

Question 6

Pharmacology

Answer 6

Ondansetron is a serotonin receptors antagonist which works by blocking receptors both centrally and peripherally. Ondansetron blocks initiation of vomiting reflexes as well as blocking the chemoreceptor trigger zone (CTZ)

Question 7

IV effects

Answer 7

Onset - 5mins
Peak - 10mins
Duration - 2.5 to 6.1hrs

Question 8

ODT effects

Answer 8

Onset - 2mins
Peak - 20mins
Duration - 120mins

Question 9

Metabolism

Answer 9

Metabolised by the liver