Anti-Depressants - TCA

Question 1

Tricyclic antidepressants
- therapeutic effect
- mechanism of action

Answer 1

• therapeutic effect: TCA primarily act as reuptake inhibitors for noradenraline (NA) and serotonin (5-HT)
• action - leads to increased levels of NA and 5-HT in the synaptic cleft - helps to alleviate depressive symptoms

Question 2

Chronic use of TCA leads to?

Answer 2

Downregulation of receptors :

Beta 1 - adrenoreceptors : involved in HR and contractility

5-HT2 receptors: involved in serotonin mediated processes

Autoreceptors: a2 and 5-HT1A/1D

Question 3

Examples of TCA - (AIL-ine)

Answer 3

Amitriptyline
Imipramine
Lofepramine

Question 4

Side effects of TCAs

Answer 4

Anti-cholinergic symptoms : inhibition of acetylcholine that regulate parasympathetic functions
- dry mouth, blurred vision, constipation, drowsiness

Anti-Histamine (H1 receptor downreg)
- sedation
- weight gain

Alpha Adrenergic antagonism
- postural hypotension
- tachycardia
- dizziness

Question 5

Drug interactions with TCA

Answer 5

• inhibition of TCA metabolism can occur - when taken with anti-psyschotics and steroids : INCREASE TOXICITY
• potentiation of alcohol and anaesthetics : can be TOXIC - lead to respiratory depression and sedation

Question 6

TCA = narrow therapeutic window, overdose of TCA leads to

Answer 6

Cardiovascular toxicity : TCA = toxic in overdose - leading to heart attacks, arrhythmias, dysrhythmias

CNS effects: convulsions, delirium, coma and respiratory distress

Narrow therapeutic window

Question 7

Risk in specific population with TCAs?

Answer 7

Those that are elderly or have dementia - due to confusion, sedation and anti-cholinergic effects

Heart disease: due to cardiotoxicity effects

Narrow therapeutic window