These are potential side effects of Selective Serotonin Reuptake Inhibitors (SSRIs):

* Light-headedness.
* Insomnia.
* Headache.
* Mouth dryness. 
* Tiredness.
* Nausea or vomiting. 
* Agitation or anxiety.  
* Diarrhea.
* Increased or decreased appetite.
* Sexual dysfunctions. 


Side Effects of Selective Serotonin Reuptake Inhibitors (SSRIs)

Selective Serotonin Reuptake Inhibitors (SSRIs) work by blocking the reabsorption of the neurotransmitter serotonin into neurons. This increases the levels of serotonin in the brain. 

SSRIs include:

- Citalopram

- Escitalopram

- Fluoxetine

- Paroxetine

- Sertraline

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Selective serotonin reuptake inhibitors (SSRIs) are a class of drugs used to treat conditions like depression, which is often associated with low serotonin levels. Unlike agonists or antagonists that bind to receptors, SSRIs work by blocking the reuptake process. This action prevents unused serotonin from being reabsorbed by the presynaptic neuron, allowing it to remain in the synaptic cleft for a longer period. The extended presence of serotonin enhances its interaction with postsynaptic receptors, thereby strengthening its overall effect. Common examples of SSRIs include Prozac, Paxil, and Zoloft.

SSRIs and SNRIs

St. John's wort has shown promise as an affordable herbal treatment for depression, being compared to tricyclic antidepressants and SSRIs, particularly with less severe forms of the disorder. However, it is also known to interact with several other drugs.

St. John's Wort

Breedlove, S. & Watson, N. (2017). Behavioral neuroscience, eighth edition. Oxford University Press.

Behavioral Neuroscience 8th Edition

National Center for Biotechnology Information (2021). PubChem Compound Summary for CID 68617, Sertraline. Retrieved October 21, 2021 from https://pubchem.ncbi.nlm.nih.gov/compound/Sertraline.

Sertraline (Zoloft)

National Center for Biotechnology Information (2021). PubChem Compound Summary for CID 43815, Paroxetine. Retrieved October 21, 2021 from https://pubchem.ncbi.nlm.nih.gov/compound/Paroxetine.

Paroxetine (Paxil)

National Center for Biotechnology Information (2021). PubChem Compound Summary for CID 2771, Citalopram. Retrieved October 21, 2021 from https://pubchem.ncbi.nlm.nih.gov/compound/Citalopram.

Citalopram (Celexa)

National Center for Biotechnology Information (2021). PubChem Compound Summary for CID 146570, Escitalopram. Retrieved October 21, 2021 from https://pubchem.ncbi.nlm.nih.gov/compound/Escitalopram.

Escitalopram (Lexapro)

National Center for Biotechnology Information (2021). PubChem Compound Summary for CID 62857, Fluoxetine hydrochloride. Retrieved October 21, 2021 from https://pubchem.ncbi.nlm.nih.gov/compound/Fluoxetine-hydrochloride.

Fluoxetine hydrochloride (Prozac)

Spielman, R. M., Jenkins, W. J., & Lovett, M. D. (2020, April 22). Psychology (2nd ed.). OpenStax. https://openstax.org/books/psychology-2e/pages/1-introduction

OpenStax Psychology (2nd ed.) Textbook

SSRIs appear to regulate the activation state of microglia in addition to their effects on the serotonergic system when studied in vitro. Fluoxetine (Prozac) and its metabolite, norfluoxetine, have been shown to induce apoptosis in microglia, which limits the amounts of neuroinflammation they can cause. There appear to be both direct and indirect (modulating amount of serotonin available to microglia, or changing the extracellular environment) mechanisms by which this is done. 

Effects of SSRIs on Microglia

Selective Serotonin Reuptake Inhibitors (SSRIs)

Selective Norepinephrine Reuptake Inhibitors (SNRIs) work by blocking the reabsorption of both serotonin and norepinephrine into neurons. This increases the levels of both these neurotransmitters in the brain.

Serotonin Norepinephrine Reuptake Inhibitors include:
- Venlafaxine

- Desvenlafaxine

- Duloxetine

Serotonin Norepinephrine Reuptake Inhibitors (SNRIs)

Although there is significant debate around psychiatric drug use during pregnancy, evidence from population-based studies show no increased risk for stillbirth or infant mortality as a result of SSRI usage during pregnancy and no increased risk of congenital malformations or stillbirth as a result of SNRI usage (specifically duloxetine) during pregnancy.

SSRI/SNRI Use During Pregnancy

The serotonin theory claims that depression and other mental disorders are caused from an imbalance of serotonin in the brain, leading to a widespread use of SSRIs. This theory was first proposed in the 1960's and was publicized in the 1990's. SSRIs aim to increase serotonin levels in the synaptic cleft by blocking the reuptake of serotonin. However, the theory has been questioned in recent years, as studies haven’t consistently found a clear link between low serotonin and mental illnesses like depression.

The Serotonin Theory

A new medication is developed to treat a mood disorder. Its mechanism involves preventing the presynaptic neuron from reabsorbing a specific neurotransmitter after it has been released into the synapse. This results in a higher concentration of that neurotransmitter remaining in the synaptic cleft for a longer time. Based on this description, what is the primary way this medication enhances the neurotransmitter's effect?

Generally speaking, depression is an overall feeling of sadness. More specifically, those with depression tend to experience several things such as: an increase or decrease in weight, troubles with concentration, feelings of meaninglessness or worthlessness, thoughts of death or suicide, and so on. 

Depression

Tricyclic (or heterocyclic) antidepressants inhibit the reuptake of serotonin and/or norepinephrine, and are thus called due to their three (or more)-ring chemical structure. Some examples include:

- Amitriptyline (Elavil) 
- Nortriptyline (Aventyl)
- Maprotiline hydrochloride (Ludiomil)
- Desipramine hydrochloride (Norpramin)
- Clomipramine (Anafranil)

A similar drug is Bupropion (Wellbutrin), which is an aminoketone that weakly blocks norepinephrine, serotonin, and dopamine reuptake.

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