Serotonin reuptake inhibitor

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Serotonin

A serotonin reuptake inhibitor (SRI) is a type of drug which acts as a reuptake inhibitor of the neurotransmitter serotonin (5-hydroxytryptamine, or 5-HT) by blocking the action of the serotonin transporter (SERT). This in turn leads to increased extracellular concentrations of serotonin and, therefore, an increase in serotonergic neurotransmission. It is a type of monoamine reuptake inhibitor (MRI); other types of MRIs include dopamine reuptake inhibitors and norepinephrine reuptake inhibitors.

Contents

SRIs are not synonymous with selective serotonin reuptake inhibitors (SSRIs), as the latter term is usually used to describe the class of antidepressants of the same name, and because SRIs, unlike SSRIs, can either be selective or non-selective in their action. For example, cocaine, which non-selectively inhibits the reuptake of serotonin, norepinephrine, and dopamine, is an SRI but not an SSRI.

SRIs are used predominantly as antidepressants (e.g., SSRIs, SNRIs, and TCAs), though they are also commonly used in the treatment of other psychological conditions such as anxiety disorders and eating disorders. Less often, SRIs are also used to treat a variety of other medical conditions including neuropathic pain and fibromyalgia (e.g., duloxetine, milnacipran), and premature ejaculation (e.g., dapoxetine) as well as for dieting (e.g., sibutramine). Additionally, some clinically used drugs such as chlorpheniramine, dextromethorphan, and methadone possess SRI properties secondarily to their primary mechanism of action(s) and this contributes to their side effect and drug interaction profiles.

A closely related type of drug is a serotonin releasing agent (SRA), an example of which is fenfluramine.

Comparison of SRIs

Binding profiles

Binding affinities of SRIs at MATs [1] [2]
Medication SERT Tooltip Serotonin transporter NET Tooltip Norepinephrine transporter DAT Tooltip Dopamine transporter
Citalopram 1.16407028100
Desmethylcitalopram 3.6182018300
Escitalopram 1.1784127410
Femoxetine 11.07602050
Fluoxetine 0.812403600
Fluvoxamine 2.213009200
Norfluoxetine 1.471426420
Paroxetine 0.1340490
Sertraline 0.2942025
Desmethylsertraline 3.0390129
Zimelidine 152940011700
Levomilnacipran [3] 19.010.5ND
Venlafaxine 8.910609300
Vilazodone [3] 1.6NDND
Vortioxetine [3] 5.4NDND
Amitriptyline 4.30353250
Clomipramine 0.28382190
Imipramine 1.40378500

SERT occupancy

SERT occupancy by SRIs at clinically approved dosages
MedicationDosage range
(mg/day) [4]
~80% SERT
occupancy
(mg/day) [5] [6]
Ratio (dosage /
80% occupancy)
Citalopram 20–40400.5–1
Escitalopram 10–20101–2
Fluoxetine 20–80201–4
Fluvoxamine 50–350700.71–5
Paroxetine 10–60200.5–3
Sertraline 25–200500.5–4
Duloxetine 20–120300.67–2
Venlafaxine 75–375751–5
Clomipramine 50–250105–25

List of SERT-selective SRIs

Many SRIs exist, an assortment of which are listed below. Note that only SRIs selective for the SERT over the other monoamine transporters (MATs) are listed below. For a list of SRIs that act at multiple MATs, see other monoamine reuptake inhibitor pages such as SNRI and SNDRI.

Selective serotonin reuptake inhibitors (SSRIs)

Marketed

Discontinued

Never marketed

Dual serotonin reuptake inhibitors and serotonin receptor modulators

Marketed

Never marketed

Serotonin reuptake inhibition as a weaker/unintended secondary effect

Marketed

Never marketed

See also

Related Research Articles

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Monoamine transporters (MATs) are proteins that function as integral plasma-membrane transporters to regulate concentrations of extracellular monoamine neurotransmitters. The three major classes are serotonin transporters (SERTs), dopamine transporters (DATs), and norepinephrine transporters (NETs) and are responsible for the reuptake of their associated amine neurotransmitters. MATs are located just outside the synaptic cleft (peri-synaptically), transporting monoamine transmitter overflow from the synaptic cleft back to the cytoplasm of the pre-synaptic neuron. MAT regulation generally occurs through protein phosphorylation and post-translational modification. Due to their significance in neuronal signaling, MATs are commonly associated with drugs used to treat mental disorders as well as recreational drugs. Compounds targeting MATs range from medications such as the wide variety of tricyclic antidepressants, selective serotonin reuptake inhibitors such as fluoxetine (Prozac) to stimulant medications such as methylphenidate (Ritalin) and amphetamine in its many forms and derivatives methamphetamine (Desoxyn) and lisdexamfetamine (Vyvanse). Furthermore, drugs such as MDMA and natural alkaloids such as cocaine exert their effects in part by their interaction with MATs, by blocking the transporters from mopping up dopamine, serotonin, and other neurotransmitters from the synapse.

<span class="mw-page-title-main">Serotonin–norepinephrine reuptake inhibitor</span> Class of antidepressant medication

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<span class="mw-page-title-main">Clomipramine</span> Antidepressant

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<span class="mw-page-title-main">Reuptake inhibitor</span> Type of drug

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<span class="mw-page-title-main">Selective serotonin reuptake inhibitor</span> Class of antidepressant medication

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<span class="mw-page-title-main">Dapoxetine</span> Medication used to treat premature ejaculation

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<span class="mw-page-title-main">PPPA (drug)</span> Chemical compound

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