Neuropharmacology — Serotonin Syndrome

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2010A Q13

Exam question

Describe the physiological basis of the effects seen in the serotonin syndrome (80% marks). List the classes of drugs that may cause the serotonin syndrome (20% marks).

CICMWrecks answer

Master answer

Serotonin (5-HT or 5-Hydroxytryptophan)

an amine neurotransmitter mainly in the CNS and GI tract
Action on Family of receptors
- Gq-Coupled, Excitatory, ↑ DAG and IP3
  - 5-HT2: CNS/PNS, GIT, Plts and Blood vessels
- Gs-Coupled, Excitatory, ↑ cAMP
  - 5-HT4: CNS/PNS, GIT
  - 5-HT6: CNS
  - 5-HT7: CNS,GIT and Blood vessels
- Gi-Coupled, Inhibitory, ↓ cAMP
  - 5-HT1: CNS and Blood Vessels
  - 5-HT5: CNS
- Ligand gated Na or K, Excitatory
  - 5-HT3: CNS/PNS and GIT
Main actions
- CNS
  - Inhibitory effect on pain pathways
  - Inhibitory effect on higher cortical function, stabilising mood and decreasing wakefulness
- CVS:
  - 5HT-2 – SMC, vasoconstriction
  - Direct small positive chronotropic and inotropic effects
- GIT:
  - ↑↑ tone and peristalsis in the GI tract

Symptoms of Serotonin Syndrome

Increased levels of serotonin in the CNS
CNS Mediated
- hyper-reflexia
- tremor
- clonus
- skeletal muscle contraction and hyperthermia
Peripheral effects
- hypertension
GIT effects
- diarrhoea.

Classes of Drugs which can cause Serotonin Syndrome

Antidepressants
- SSRI, SNRI, MAOi, TCA
Other
- amphetamines
- pethidine, tramadol
- Methylene Blue
- Sumatriptan (5-HT1 agonist)

Gladwin 2016

Answer by Gladwin

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Exam appearances

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Exam	Exact exam wording	Candidate success
2010A Q13	Describe the physiological basis of the effects seen in the serotonin syndrome (80% marks). List the classes of drugs that may cause the serotonin syndrome (20% marks).	70%