Antidepressants (SSRI, SNRI, NDRI, Tricyclics)

Antidepressants are used in the treatment of depressive disorders (e.g. major depressive disorder, dysthymia). They can also be used for other conditions, such as anxiety disorders.




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There are six major classes of antidepressants, but I shall only talk about four of them:

Selective serotonin reuptake inhibitors (SSRI)
Serotonin and Noradrenaline Reuptake Inhibitors (SNRIs)
Norepinephrine and dopamine reuptake inhibitors (NDRIs)
Tricyclic Antidepressants

Selective serotonin reuptake inhibitors (SSRIs)

SSRIs are the most commonly prescribed antidepressants. Apart from being effective in treating depression, it also has fewer side-effects as compared to other antidepressants. They work by blocking the absorption of serotonin in the brain. Serotonin has been found to affect not just mood, but other factors such as digestion and sleep. SSRIs are also used in the treatment of anxiety disorders, eating disorders, and chronic pain.

Note: SSRIs may increase the risk of suicide, especially in children and adolescents.

Serotonin and Noradrenaline Reuptake Inhibitors (SNRIs)

SNRIs raise levels of serotonin and norepinephrine, two neurotransmitters in the brain – they both play a key role in stabilising mood. They are sometimes used for treatment of anxiety disorders and attention deficit hyperactivity disorder (ADHD).

Side effects include, but are not limited to:

Anxiety or agitation
Difficulty urinating
Loss of appetite
Reduced sexual desire, or problems with sexual arousal

Norepinephrine and dopamine reuptake inhibitors (NDRIs)

NDRIs affect the reuptake of norepinephrine and dopamine are another class of reuptake inhibitors. They are sometimes used in the treatment of addiction and ADHD. The only NDRI that is approved by the Food and Drug Administration (FDA) to use for treating depression is buproprion (Wellbutrin). Some of the more serious (but rare) side effects are ringing in the ears, shakiness, and frequent urination.

Tricyclic Antidepressants

Tricyclics  are sometimes used in the treament of some anxiety disorders, fibromyalgia, and chronic pain. Tricyclics are not often used today due to the number and severity of side effects. Some of the side effects are seizures, hypertension (high blood pressure), and arrhythmia (irregular heartbeat).


Again, note that there are other classes of antidepressants that have not been mentioned in this article. Medications that are not antidepressants may also be used in the treatment of depression. Before being prescribed with a particular medication or having a dosage increased, it is useful to know the possible side effects so you know what signs to look out for. If the side effects are too overwhelming, call your psychiatrist about it. Not everyone responds to a medication the same way – just because you hear horror stories of side effects doesn’t mean that you will get those side effects too. Alcohol and other medication could interact with your current medication – consult your psychiatrist for more information.

Examples of some websites that give a good overview of medication and their side effects:
WebMD – All possible side effects are listed by likelihood and severity.
Drugs.com – Description, explanation, dosage, etc.

Resources, Links & Sources:

  • Trivedi, J., Tripathi, A., Nischal, A., & Nischal, A. (2012). Suicide and antidepressants: What current evidence indicates. Mens Sana Monographs, 10(1) doi:10.4103/0973-1229.87287
  • http://www.medicalnewstoday.com/kc/antidepressants-work-248320\
  • http://www.webmd.com/depression/how-different-antidepressants-work#1
  • http://www.everydayhealth.com/snri/guide/
  • https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3353604/
  • http://www.treatment4addiction.com/drugs/antidepressants/norepinephrine-dopamine-reuptake-inhibitors-ndris/

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