- Anti-emetics
- Vomiting - the forced explosion of gastric contents in a highly co-ordinator manner
- Wrenching is followed by abdominal wall muscle contraction
- Intercostals, pharyngeal and laryngeal muscles all co-ordinate to protect larynx during vomiting
- Anti-emetics
- Dopamine antagonists (avoid in Parkinson's disease)
- Phenothiazines
- Mainly used as antipsychotics and can cause extra pyramidal side effects
- Propilamines
- Piperazines
- Piperidines
- Butyrophenones
- Benzamides
- 5HT₃ receptor antagonists
- Anticholinergics (also avoid in Parkinson's due to the risk of central anticholinergic syndrome)
- Antihistamines
- Miscellaneous
- Dexamethasone, propofol, benzodiazepines, cannabinoids
- Multiple receptors involved
- D₂
- HT₃
- Opioid
Link:Opiates
- H₁
- Muscarinic ACh
- PSNS and vestibular apparatus
- NK1
- Gut
- Target for future anti-emetics
- Specific common drugs
- Ondansetron
- A carbazole drug with central and peripheral effects
Link:en.wikipedia.org/wiki/carbazole
- Blocks PSNS afferents from the gut via antagonism of 5HT₃ and works centrally at the CTZ
- Bioavailability 60%, 75% protein bound, T½(e) 3 hrs
- Undergoes hepatic hydroxylation and conjugation
- Clearance 0.45L/kg/hr
- Constipation, headache and dizziness are the commonest side effects
- Cyclizine
- Piperazine derivative
- Used at dose of 1mg/kg or 50mg in adults
- Used in motion sickness and PONV
- H₁ receptor antagonism
- Anticholinergic side effects
- Metabolised to nor-cyclizine (demethylated) in the liver
- T½(e) - 10hrs
- Metoclopramide
- Benzamide derivative
- Prokinetic action
- Works in the gut, CTZ and at peripheral D₂ receptors
- Has some action at 5HT₃ receptors
- 1st pass metabolism of 50-90%, 20% proteins bound
- Hepatically metabolised or eliminated unchanged (50%)
- S/E include dystonic reactions and occulogyric crisis - treat with benzatropine or procyclidine