Mental health
SNRIs
Serotonin–noradrenaline reuptake inhibitors — Antidepressants that also help certain nerve-pain and anxiety 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
SNRIs are used for depression and several anxiety disorders, and some (such as duloxetine) are also licensed for nerve pain. They are often chosen when an SSRI has been ineffective or poorly tolerated.
How it works
They increase the available levels of both serotonin and noradrenaline in the brain by blocking their reuptake. The noradrenaline effect is thought to add to the antidepressant action and to help with pain.
In practice
In practice SNRIs are a common second step when an SSRI has not worked or is not tolerated, and they are useful where neuropathic pain coexists with low mood. The trade-off is a more noticeable effect on blood pressure (worth checking, especially at higher doses) and a brisk discontinuation syndrome if stopped abruptly — venlafaxine in particular needs a careful taper. As with all antidepressants, watch mood and any emerging suicidal thoughts closely in the first weeks and in younger patients.
Examples
Practical use
How to take it & use it well
- Take your SNRI regularly as prescribed, usually once daily with food, and at the same time each day.
- Allow several weeks for the full benefit, as the effect on mood builds up gradually.
- Do not stop suddenly, as this can cause unpleasant discontinuation symptoms; reductions should be made gradually with your prescriber.
- Have your blood pressure checked, as these medicines can raise it in some people.
- Seek advice if you notice worsening mood or new thoughts of self-harm, especially in the first weeks.
Common uses
- Depression
- Generalised anxiety and other anxiety disorders
- Diabetic and other neuropathic pain (duloxetine)
Monitoring
- Mood and any suicidal ideation, especially in the first weeks and in the young
- Blood pressure
- Response and tolerability
Weighing it up
Advantages & disadvantages
Advantages
- They are effective for depression and several anxiety conditions.
- Duloxetine can also help certain types of nerve pain.
- They are usually taken just once a day, which is convenient.
- They offer an alternative for people who have not responded well to other antidepressants.
Disadvantages
- They can raise blood pressure, which may need monitoring.
- Stopping abruptly often causes discontinuation symptoms such as dizziness, flu-like feelings and electric-shock sensations, with venlafaxine especially prone to this.
- Common side effects include nausea, sweating, dry mouth and sleep changes.
- They can occasionally affect sexual function or cause increased anxiety early in treatment.
Key safety principles
What to watch for
- Can raise blood pressure — monitor, particularly at higher doses.
- Marked discontinuation symptoms if stopped suddenly — taper gradually (especially venlafaxine).
- Risk of serotonin syndrome when combined with other serotonergic drugs; monitor mood early in treatment.
Key interactions
What to avoid or check alongside
- Combined with other serotonin-raising drugs, such as some painkillers, triptans or other antidepressants, they increase the risk of serotonin syndrome.
- Taken with monoamine oxidase inhibitors they can cause dangerous reactions, so a gap between the medicines is essential.
- With anticoagulants or anti-inflammatory painkillers the risk of bleeding rises.
- Combined with other medicines that raise blood pressure, the effect can add up.
- Some medicines that change liver enzymes can alter SNRI levels and effects.
Patient & carer advice
- It may take several weeks to feel the full benefit
- Do not stop abruptly — we will reduce the dose slowly
- Report agitation, worsening mood or thoughts of self-harm promptly
Use with
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Answers
SNRIs: frequently asked questions
What are SNRIs used for?
They treat depression and several anxiety disorders, and one, duloxetine, is also used for certain types of nerve pain.
Why should I not stop my SNRI suddenly?
Stopping abruptly often causes discontinuation symptoms such as dizziness, flu-like feelings and electric-shock sensations. Reducing gradually with your prescriber lowers this risk.
Do SNRIs affect blood pressure?
They can raise blood pressure in some people, so your prescriber may check it during treatment, particularly when starting or increasing the dose.
How long do SNRIs take to work?
Mood usually improves gradually over several weeks. It is important to keep taking the medicine and stay in touch with your prescriber during this time.
What is serotonin syndrome?
It is a rare but serious reaction from too much serotonin activity, causing agitation, sweating, shivering and a fast heartbeat. It is more likely when combining serotonin-raising drugs, and needs urgent care.
Authoritative sources
Always verify against the source
This overview is for orientation. For doses, interactions, contra-indications and the full monograph, use:
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