Core pharmacology

Class Group

Anti-emetic

Serotonin Antagonist

Legacy Cicm Level

Level 3

Introduction

5-HT3 antagonist antiemetic

Presentation

Clear, colourless solution, oral wafer, oral tablet and suppository
0.1mg/kg in paeds

Mechanism of action

- Peripheral in GIT 5-HT3-R inhibited, preventing afferent signal to medulla
- Central at VC and CTZ

Adverse Effects Toxicity

1. Mild QTc
2. Flushing, headache, constipation
3. Bradycardia after rapid infusion may occur
4. Choreaform movements in overdose

Absorption

Passive and complete oral absorption with BA 65%

Protein binding

75% PB

Volume of distribution

Vd 2L/kg

Metabolism

- Extensive hepatic metabolism (including CYP 3A4 and 2D6)
- Due to extensive metabolism, enzyme inhibition easily compensated for by other enzymes

Excretion

<5% renally excreted unchanged

Half-life

T1/2= 3 hours

Special Points

Hepatic impairment: 100% BA, T1/2=30 hours (limit to 8mg/day)