2009A07 Outline the subtypes of serotonin (5-hydroxytryptamine) receptors.
Discuss pharmacological agents that act at these sites.

 

List:

·     Intro

·     Serotonergic drugs

·     Serotonin syndrome

 

Intro:

·       Monoamine receptor in CNS, PNS, vascular smooth muscle (dilate and constrict), platelets

·       Multiple subtypes: 1ABCD, 2ABC, 3, others

·       Mostly metabotropic GPCR, except 5HT3 ligand-gated ion channel (activity -> depolarisation)

·       Both excitatory and inhibitory

 

Serotonergic drugs by class:

Anti-depressants

·  SSRI (e.g. fluoxetine)

·  SNRI (e.g. duloxetine)

·  TCA (e.g. amitryptiline)

·  MAOi (e.g. moclobemide)

Anti-emetics

·  5-HT3 antagonists (e.g. ondansetron)

·  Metoclopramide (central 5-HT3 antagonist, peripheral 5-HT4 agonist

Non-opioid analgesics

·  Paracetamol (5-HT1A)

·  Ketamine

Opioid analgesics

·  Tramadol

·  Methadone

·  Pethidine

Anaesthetic agents

·  Halogenated ether anaesthetics

·  Propofol

·  Ketamine

Other

·  5HT1D: sumatriptan

·  5HT2: ketanserin, methylsergide, pizotifen

·  5HT2A: ergometrine, phenoxybenzamine

·  LSD: ?

 

Serotonin syndrome:

Cause

·  Multiple drugs increasing serotonergic activity

·  Especially MAOi

Features

·  Autonomic: ↑HR, ↑BP, shivering, sweating, dilated pupils

·  Somatic NS: hyperreflexia, myoclonus

·  CNS: agitation

·  GIT: abdo pain, nausea/vomiting, diarrhoea

Treatment

·  Cyproheptadine

·  Supportive