TCA OD

Question 1

What is side effect of TCAs?

Answer 1

Anticholinergic

Result: less PNS -> more SNS activity

Examples:

• dilated pupils
• tachycardia
• dry mouth
• urinary retention
• blocks alpha1 adrenal receptors in blood vessels -> lower blood pressure as vasoconstriction is blocked -> more vasodilatation
• coma
• fast sodium channels in the heart are blocked -> arrythmais
• seizures -> due to GABA antagonist

Question 2

Signs of TCAs OD on ECG

Answer 2

ECG with TCAs OD

• tachycardia
• R axis deviation (lead I and aVF - ‘returning/reaching’)
• widen QRS

Question 3

Management of TCAs OD

Answer 3

odium bicarbonate -> if ECG changes (to increase the bioavailability of sodium, as sodium channel blocked) + buffer against seizures and acts against acidosis

Question 4

What drug and why is contraindicated in the treatment of TCAs OD induced seizures?

Answer 4

Phenytoin is contraindicated

This is because it acts as Na+ channel blocker and in TCAs OD we have already blocked Na+ channels -> risk of arrhythmias would be increased

Question 5

Would haemodialysis work in management of TCAs OD?

Answer 5

No, as TCAs are protein bound

Question 6

How to differentiate anti-psychotics OD from TCAs?

Answer 6

Anti-psychotic meds also block dopamine-2 receptors -> involuntary movements are not blocked

Involuntary movements: pseudoparkinsonism, acute dystonia, tardive dyskinesia