Tricyclic antidepressants

Tricyclics block the norepinephrine (NET) and serotonin (SERT) transporters, so both transmitters build up in the synapse; how this relieves depression is not fully known. They also block muscarinic, H1-histamine and α1-adrenergic receptors, giving dry mouth, sedation and postural hypotension, and they block sodium channels, which widens the QRS complex and makes overdose dangerous to the heart.

• AmitriptylineWidely used at low doses for nerve pain and migraine prevention as well as for depression; it is usually taken in the evening because it causes sleepiness.
• NortriptylineLess anticholinergic than its parent drug amitriptyline; its blood level can be measured to keep it within a target range.

• Depression
• Nerve pain (neuropathic pain)
• Migraine prevention

• Dry mouth, constipation and blurred visionKnown for
• DrowsinessKnown for
• Heart block and arrhythmiasKnown forSerious
• Dizziness on standing (orthostatic hypotension)
• Difficulty passing urine
• Weight gain
• Confusion, especially in older people
• SeizuresSerious
• Suicidal thoughts in children and young adultsSerious
• Nausea, headache and malaise if stopped abruptly

What the class has in common. Each drug's card has its own, and Known for marks what an exam expects you to know.

• Very toxic in overdose (arrhythmias, seizures, coma), so supply small amounts to anyone at risk of suicide.
• Avoid in the recovery period after a heart attack, and take care with heart block or other heart disease.
• Their atropine-like action can bring on angle-closure glaucoma or urinary retention in people at risk.
• Never combine with an MAOI; leave at least 14 days after stopping one.

Written for biofideX in plain words, after checking these references:

• Antidepressants (NHS)
• Tricyclic Antidepressant (NCI Thesaurus)
• Amitriptyline hydrochloride tablets: label (DailyMed)
• Amitriptyline 25 mg film-coated tablets: SmPC (emc)

For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.