Serotonin Norepinephrine Reuptake Inhibitors (SNRIs)


Overview: Serotonin Norepinephrine Reuptake Inhibitors (SNRIs) are a class of antidepressants that are used to treat several mental health conditions. They are primarily used for Depression, though can also be used for Anxiety and Post-traumatic stress disorder. SNRIs are the second-most prescribed class of antidepressants, only trailing to SSRIs. They were created later than SSRIs.





How do they work?: It isn’t entirely known how SNRI antidepressants work. It is believed that the tablets inhibit the reuptake of serotonin and norepinephrine, helping to regulate mood and emotion. Unlike SSRIs, SNRIs act upon norepinephrine as well. SNRIs work best when used in conjunction with some form of psychotherapy.


How effective are they?: Research on the efficacy of SNRI antidepressants is mixed. Many suggest SNRIs are actually better than SSRIs for treating depression, yet aren’t tolerated as well. Research suggests SNRIs are useful for Anxiety. SNRI antidepressants do help many people recover or manage mental health conditions.


Treatment Course: SNRI Antidepressants generally come in tablet form, though some can be injected or taken as a liquid if required. Once prescribed, a low dose will initially be prescribed. A typical treatment course lasts six months., though it can often rise to around 18 months, or even indefinite use. Unfortunately, it takes at least two weeks for benefits to be felt. At first, your mood may start to increase again. The full benefits of antidepressants normally take up to six weeks to be felt. If after this point you haven’t witnessed an improvement, it is worth talking to your GP or mental health specialist. They may suggest switching antidepressants. Many people succeed on their second antidepressant. It is highly likely you will experience some mild side effects early in the treatment. It is crucial however to not stop taking the tablets, as these side effects will disappear quickly. The commonly prescribed SNRI antidepressants can be prescribed by a GP.


Types of SNRI antidepressants: Due to how recently they were created, there aren’t many SNRIs. Only two are primarily used in the United Kingdom. Each medication has its own dedicated page.



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Side Effects

We recommend consulting the individual page for each antidepressant for information on side effects – as they differ from tablet to tablet. Furthermore, the leaflet that comes with each pack of tablets contains enhanced information on side effects. Side effects generally are only present in the first few days of treatment, with the body needing time to get used to treatment. You will often see a GP during the first month of treatment to see how you are reacting.


SNRI’s are associated with loss of appetite, headaches, shakiness, anxiety, sickness, sexual dysfunction and increase in suicidal thoughts in the first few days. The information leaflet with each medicine will include full instructions and information on the side effects. An overdose could induce serotonin syndrome, so should therefore be avoided.




As with any medication, you must be careful when taking antidepressants. Your GP or mental health professional should make you aware of any types of medicine or foods that you should avoid. Some frequently used medications, even over-the-counter ones shouldn’t be used with antidepressants. It is worth looking at the individual page of each antidepressant to see cautions, but an overview is provided here.


Other Medicines: Ibuprofen and aspirin are often not recommended when using SNRI antidepressants. Each information leaflet will provide the types of medicines not to be used. It is important NOT to combine medicines from different classes of antidepressants, or take two from one class at the same time. You should also avoid the herbal remedy St John’s Wort.


Alcohol: Alcohol acts as a depressant, therefore it is recommended that anyone taking an antidepressant stays away from drinking alcohol.


Pregnancy and Breastfeeding: Antidepressants generally aren’t recommended for pregnant women. Taking antidepressants while breastfeeding also isn’t recommended.


Young People: People under the age of 18 are rarely prescribed antidepressants, instead being offered therapy. The exception to this is the SSRI Fluoxetine (Prozac). If therapy hasn’t worked, antidepressants can be prescribed. People under the age of 25 taking antidepressants have been shown to be vulnerable to suicidal thoughts – a serious side effect.


Illicit Drugs: The use of illegal or recreational drugs isn’t recommended, as they can react unpredictably with antidepressants. Cannabis, cocaine, heroin and ketamine have been known to particularly worsen symptoms.


As always, ensure you read the information leaflet.