Mental health
Tricyclic antidepressants
TCAs — Older antidepressants now used more often at low dose for nerve pain and other conditions.
Education and reference only. This is a plain-language class overview — it deliberately contains no doses. Always check the current Summary of Product Characteristics (SmPC), the BNF and your local formulary before prescribing or administering any medicine.
What it is
Tricyclic antidepressants are an older class still used for depression in some cases and, commonly at lower doses, for neuropathic pain, migraine prophylaxis and other off-label uses.
How it works
They increase available noradrenaline and serotonin in the brain, but also block several other receptors — which is what produces both their pain-relieving effects and their characteristic side-effects.
In practice
In practice TCAs are used less for depression today (SSRIs are better tolerated and far safer in overdose) but remain valuable at low dose for neuropathic pain, migraine prevention and some other indications. The key cautions are dangerousness in overdose, anticholinergic effects and QT prolongation — so they need care in older people, in those with heart disease, and where overdose risk is a concern.
Examples
Practical use
How to take it & use it well
- When used at low doses for nerve pain, take amitriptyline at night, as it often causes drowsiness that can also help with sleep.
- It is usually started low and increased slowly, so allow time and follow the plan your prescriber gives you.
- Take it at the same time each evening, with or without food.
- If you miss a dose, skip it and take the next one at the usual time rather than doubling up.
- Do not stop suddenly after regular use, as you may feel unwell; reduce gradually with advice.
- Keep it well out of reach of children, as it is dangerous in overdose.
Common uses
- Neuropathic pain (low dose)
- Migraine prophylaxis
- Depression (selected cases)
Monitoring
- Mood and any suicidal ideation when used for depression
- ECG/QT where cardiac risk exists
- Tolerability, especially in older people
Weighing it up
Advantages & disadvantages
Advantages
- At low doses it can ease certain types of nerve pain that ordinary painkillers do not help.
- Taken at night, it may also improve sleep.
- It is well established and inexpensive.
- It can be useful for some types of chronic pain and headache prevention.
- A once-daily evening dose is simple to remember.
Disadvantages
- It commonly causes drowsiness, a dry mouth, constipation and blurred vision.
- It is especially dangerous in overdose, so quantities and storage need care.
- It can cause a fast heartbeat and light-headedness on standing, particularly in older adults.
- Pain relief can take a few weeks to build up, so it is not an instant fix.
- It needs to be reduced gradually rather than stopped abruptly after regular use.
Key safety principles
What to watch for
- Dangerous and potentially fatal in overdose — prescribe with care where risk exists.
- Anticholinergic effects (dry mouth, constipation, urinary retention, confusion in the elderly).
- QT prolongation and caution in heart disease; sedation and weight gain are common.
Key interactions
What to avoid or check alongside
- Alcohol and other sedating medicines add to drowsiness and slowed reactions.
- Combining with other medicines that affect heart rhythm can increase the risk of rhythm problems.
- Used with certain antidepressants and some other drugs, there is a risk of too much serotonin activity, which can be serious.
- Some medicines for bladder problems and certain antihistamines add to dry mouth, constipation and blurred vision.
- Tell your prescriber about all your medicines, as tricyclics interact with many.
Patient & carer advice
- Drowsiness is common — take at night and take care driving
- Do not stop suddenly; taper with advice
- Even at low "pain" doses, take exactly as prescribed
Use with
Related clinical calculators
Dose and risk decisions for this class often depend on renal function, weight or bleeding/stroke risk. These tools help:
Answers
Tricyclic antidepressants: frequently asked questions
Why am I on an antidepressant for pain?
At low doses, amitriptyline can calm overactive nerve signals and ease nerve-related pain. This use is separate from its higher-dose use for depression.
Why is it taken at night?
It often causes drowsiness, so taking it in the evening means the sleepy effect is more helpful and less disruptive during the day.
How long until it helps my pain?
It can take a few weeks of regular use, often with a slow dose increase, before you notice the full benefit.
Why is it considered dangerous in overdose?
Tricyclics can seriously affect the heart and brain if too much is taken. Keep them safely stored and never take more than prescribed.
Can I stop it suddenly?
No. After regular use it should be reduced gradually with advice, as stopping abruptly can make you feel unwell.
Authoritative sources
Always verify against the source
This overview is for orientation. For doses, interactions, contra-indications and the full monograph, use:
Related guides
Need a custom medicines or prescribing resource?
We build evidence-led clinical references, calculators and decision aids for teams.