Psychiatry/Tricyclic antidepressant

Tricyclic antidepressants

also: amitriptyline · clomipramine · nortriptyline · lofepramine

Overview

Older antidepressants — now rarely first-line for depression because of anticholinergic effects and danger in overdose, but used for neuropathic pain, migraine prophylaxis and OCD (clomipramine).

Mechanism

Block serotonin AND noradrenaline reuptake, but also antagonise muscarinic, H1 and α1 receptors → the characteristic side effects and overdose toxicity (Na-channel blockade → arrhythmia).

Indications

Depression (second/third-line)
Neuropathic pain / migraine prophylaxis (amitriptyline — low dose)
OCD (clomipramine)

The agents

Amitriptylinesedating

low-dose for pain

Neuropathic pain, migraine prophylaxis, sleep.

Clomipramineserotonergic

OCD.

Lofepraminesafer in overdose

Less toxic TCA option.

Adverse effects

Overdose: cardiotoxicity (broad QRS, arrhythmia) + seizuresserious

Dangerous in overdose — AVOID if significant suicide risk; treat with IV bicarbonate.

Anticholinergic (dry mouth, constipation, urinary retention, blurred vision)classic

Postural hypotension, sedation (H1)common

QT prolongationcommon

Cautions & contraindications

Recent MI / arrhythmia / heart blockall

Significant suicide riskall

Lethal in overdose.

Within 2 weeks of an MAOIall

Interactions

MAOIs, other serotonergics, antimuscarinics; QT-prolonging drugs

Monitoring & kinetics

ECG if cardiac risk; mood/suicidality

Oral. Low doses for pain; antidepressant doses higher.

Source: BNF — Tricyclic antidepressants