2007 Second Sitting Paper 1 Question 3 - WordPress.comFeb 03, 2007 · 2007 Second Sitting Paper 1...
Transcript of 2007 Second Sitting Paper 1 Question 3 - WordPress.comFeb 03, 2007 · 2007 Second Sitting Paper 1...
2007 Second Sitting Paper 1 Question 3
2007-2-3 Describe the physiological effects and principals of management of
tricyclic antidepressant overdose.
TCA (e.g. amitryptilline and imipramine)
- Toxic dose of amitrytilline
>10mg/kg
Mechanism of Action
- Act via central inhibition of noradrenaline reuptake (via inhibition of NET) and
serotonin reuptake (via inhibition of SERT) but not dopamine transfer
- Also Na channel blockade
- Agonist at α1 and to a lesser extent α2 receptors
- Decreases sensitivity of muscarinic receptors
- Antagonist at H1 receptors
- Downregulates expression of GABAb and NMDA receptors
Physiological effects
CNS
- Agitation
- Seizures
- Coma and respiratory depression
CVS
- Sinus tachycardia
- Hypertension
- Na channel blockade
Prolonged QT
Widened QRS
RBBB
Anticholinergic
- Dry mouth
- Dry, warm skin
- Urinary retention
- Tachycardia
2007 Second Sitting Paper 1 Question 3
Management
- Maintain airway patency
- Support ventilation
- Support organ perfusion
Fluids, vasopressors as needed
- ABGs, blood tests, ECG
- Activated charcoal early
However TCA rapidly absorbed
- Sodium bicarbonate
100mmol boluses
Target pH >7.45
Alkalinization promotes protein binding and limits free fraction of drug
Alkalinization promotes dissociation of TCA and Na channel
- Consider intralipid, hypertonic saline for refractory cases