Psychopharmacology of Selective Serotonin Re-uptake Inhibitors (SSRIs) – Mechanism of Action

Posted on: April 23, 2020
Last Updated: April 23, 2020

In this video, Dr Sanil Rege covers the mechanism of action and psychopharmacology of SSRIs.

Fluoxetine, Paroxetine, Sertraline, Escitalopram and Citalopram come under the banner of SSRIs. Read more on the mechanisms of action, doses and pharmacokinetics of SSRIs here.

SSRIs are evidence-based on the treatment of depression, anxiety and OCD. SSRIs block serotonin transporter (SERT) increasing levels of serotonin.

The main receptors serotonin acts on are 5HT2A, 5HT2C, 5HT3 and 5HT1A autoreceptor. The initial activation of the post-synaptic 5HT2A, 5HT2C and 5HT3 receptors are responsible for side effects. These receptors downregulate in 1-2 weeks and the side effects wane.

The 5HT1A receptor also downregulates after a lag of 2-4 weeks (onset of action for SSRIs) which results in serotonin flowing down the presynaptic neuron and the neuron firing.