Tricyclic antidepressants

Tricyclic antidepressants

Tricyclic antidepressants (TCAs) are used less commonly now for depression due to their side-effects and toxicity in overdose

toxicity in overdose

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. They are however used widely in the treatment of neuropathic pain, where smaller doses are typically required.

The primary mechanism by which TCAs exert their antidepressant effects is through the inhibition of the reuptake of neurotransmitters

inhibition of the reuptake of neurotransmitters

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• Serotonin (5-HT): This neurotransmitter has a pivotal role in mood regulation. Inhibition of its reuptake leads to increased concentrations in the synaptic cleft, enhancing serotonergic neurotransmission.
• Noradrenaline (NA): Similar to 5-HT, blocking the reuptake of NA increases its synaptic cleft concentration, intensifying noradrenergic neurotransmission.

As well as 5-HT and NA, tricyclics interact with number of other receptors that contribute to their side-effect profile:

• antagonism of histamine receptors
  • drowsiness
    Tricyclic antidepressants may cause lethargy/drowsiness
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    Importance: 24
• antagonism of muscarinic receptors
  • dry mouth
    Tricyclic antidepressants may cause dry mouth
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    Importance: 8
  • blurred vision
    Tricyclic antidepressants may cause blurred vision
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    Importance: 9
  • constipation
    Tricyclic antidepressants may cause constipation
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    Importance: 24
  • urinary retention
    Tricyclic antidepressants may cause urinary retention, particularly in patients with BPH
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    Importance: 43
• antagonism of adrenergic receptors
  • postural hypotension
• lengthening of QT interval
  Tricyclic antidepressants may cause lengthens QT interval
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  Importance: 3

Choice of tricyclic

• low-dose amitriptyline is commonly used in the management of neuropathic pain and the prophylaxis of headache (both tension and migraine)
• lofepramine has a lower incidence of toxicity in overdose
  Lofepramine - the safest TCA in overdosage
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  Importance: 78
• amitriptyline and dosulepin
  Dosulepin - avoid as dangerous in overdose
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  Importance: 68
  (dothiepin) are considered the most dangerous in overdose

*trazodone is technically a 'tricyclic-related antidepressant'

+PassMedicine Notes

Tricyclic antidepressants (TCAs) are used less commonly now for depression due to their side-effects and toxicity in overdose. They are however used widely in the treatment of neuropathic pain, where smaller doses are typically required.

The primary mechanism by which TCAs exert their antidepressant effects is through the inhibition of the reuptake of neurotransmitters

• Serotonin (5-HT): This neurotransmitter has a pivotal role in mood regulation. Inhibition of its reuptake leads to increased concentrations in the synaptic cleft, enhancing serotonergic neurotransmission.
• Noradrenaline (NA): Similar to 5-HT, blocking the reuptake of NA increases its synaptic cleft concentration, intensifying noradrenergic neurotransmission.

As well as 5-HT and NA, tricyclics interact with number of other receptors that contribute to their side-effect profile:

• antagonism of histamine receptors
• drowsiness
• antagonism of muscarinic receptors
• dry mouth
• blurred vision
• constipation
• urinary retention
• antagonism of adrenergic receptors
• postural hypotension
• lengthening of QT interval

Choice of tricyclic

• low-dose amitriptyline is commonly used in the management of neuropathic pain and the prophylaxis of headache (both tension and migraine)
• lofepramine has a lower incidence of toxicity in overdose
• amitriptyline and dosulepin (dothiepin) are considered the most dangerous in overdose

More sedative _ Less sedative| Amitriptyline Clomipramine Dosulepin Trazodone* _ Imipramine Lofepramine Nortriptyline|

*trazodone is technically a 'tricyclic-related antidepressant'