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Selective Serotonin Reuptake Inhibitors

Q: What are the main indications for SSRIs?

The primary clinically validated areas for SSRI use: Depressive states: major depressive disorder, classic depressive states.Neuroses: especially obsessive-compulsive disorder and panic attacks; serotonergic agents, including SSRIs, are commonly used to prevent recurrent panic attacks.Post-ischemic stroke anxiety disorders: SSRIs are recommended to reduce anxiety symptoms.Climacteric syndrome: relief of vasomotor and psychoemotional symptoms, sleep improvement.Behavioral correction in dysthymic and anxious-suspicious personalities.Somatic and psychosomatic disorders.Affective disorders in multiple system atrophy: depression and anxiety, where SSRIs such as paroxetine are indicated.

Inhibitores selectivi reuptakis serotonini

For medical students2 min readUpdated 2026-10-10

Selective serotonin reuptake inhibitors selectively block neuronal uptake of the neurotransmitter, enhancing serotonergic activity in the central nervous system. Due to their selective action, they exhibit significantly fewer adverse reactions compared to tricyclic antidepressants.

MechanismBlockade of serotonin reuptake in the CNS

ParoxetineMost potent inhibitor in the group, latent period of 10–14 days

DosingParoxetine taken once daily, peak concentration in 2–8 hours

Major LimitationCombination with non-selective MAOIs is absolutely contraindicated

General Characteristics and Mechanism of Action

Selective neuronal serotonin reuptake inhibitors act directly on brain neurons. The primary biochemical process involves the inhibition of serotonin reuptake, leading to a predictable increase in serotonergic activity within the body.

Unlike non-selective agents, such as tricyclic antidepressants (TCAs), these drugs have a fundamentally different receptor profile:

They exhibit minimal or completely absent antimuscarinic (anticholinergic) activity.
They have only a negligible effect on alpha-adrenergic receptors and histamine receptors.

The main clinical advantage of this profile is a substantially lower frequency of side effects typically caused by undesirable blockade of peripheral receptors.

Pharmacodynamics and Characteristics of Paroxetine

A prominent representative of this group is paroxetine. Its pharmacodynamic action is based on the preferential blockade of neuronal serotonin reuptake. Notably, among all known drugs in this class, it is considered the most potent inhibitor.

Clinical effects develop gradually with regular administration:

The antidepressant effect appears after a latent period averaging 10 to 14 days.
The spectrum of action includes marked reduction of anxiety, alleviation of depressive symptoms, and general correction of sleep disorders.
The primary clinical indication is major depressive disorder.

Similarly to the broader drug class, paroxetine compares favorably to tricyclic antidepressants by having less pronounced antimuscarinic effects and weak antihistaminic activity.

Pharmacokinetics and Distribution

Compounds in this class possess specific pharmacokinetic properties. The drugs are characterized by a large volume of distribution: they actively accumulate in body tissues, whereas only about 1% of the administered dose circulates in blood plasma.

Paroxetine is characterized by the following parameters:

Absorption: completely absorbed from the gastrointestinal tract.
Metabolism: undergoes intensive first-pass hepatic metabolism, which reduces overall bioavailability. Food intake does not affect the degree of absorption.
Regimen: standardly prescribed once daily.
Concentration: peak plasma concentration is reached within 2–8 hours, while steady-state concentration is established after 7–14 days of regular intake.

Safety Profile and Drug Interactions

Despite good tolerability, SSRIs have a certain spectrum of adverse reactions. Frequent side effects include dyspeptic disorders such as nausea, headaches (cephalalgia), and skin pruritus. Autonomic disturbances are less common: mydriasis, accommodation disorders, tachycardia, arrhythmias, and orthostatic hypotension.

Characteristics of other representatives:

Fluvoxamine is completely devoid of sedative action and does not affect peripheral cholinergic and adrenergic receptors.
Sertraline successfully combines antidepressant properties with a mild sedative effect, also without affecting peripheral innervation.

Critical Risk: Combining SSRIs with non-selective monoamine oxidase (MAO) inhibitors is an absolute contraindication. Excessive accumulation of serotonin in the synaptic cleft causes serotonin syndrome with a dangerous clinical presentation: ranging from confusion and psychomotor agitation to muscle rigidity, hyperthermia, and cardiovascular collapse. Prevention requires a mandatory washout period of at least two weeks.

Mnemonic

Paroxetine is a "potent syrup": the strongest serotonin inhibitor, taken once daily, but combining with MAOIs is strictly prohibited (remember the two-week "washout" period!).

Frequently asked questions

What drugs are included in the selective serotonin reuptake inhibitor class?

The SSRI class includes the following drugs, whose mechanism of action involves the preferential blockade of neuronal serotonin reuptake:

Paroxetine (Paroxetine) — considered the most potent inhibitor in the group;
Fluvoxamine — devoid of sedative effects;
Sertraline (Sertraline) — combines antidepressant and sedative effects;
Fluoxetine (Fluoxetine) — possesses psychostimulating properties;
Citalopram (Citalopram);
Escitalopram (Escitalopram).

What are the main indications for SSRIs?

The primary clinically validated areas for SSRI use:

Depressive states: major depressive disorder, classic depressive states.
Neuroses: especially obsessive-compulsive disorder and panic attacks; serotonergic agents, including SSRIs, are commonly used to prevent recurrent panic attacks.
Post-ischemic stroke anxiety disorders: SSRIs are recommended to reduce anxiety symptoms.
Climacteric syndrome: relief of vasomotor and psychoemotional symptoms, sleep improvement.
Behavioral correction in dysthymic and anxious-suspicious personalities.
Somatic and psychosomatic disorders.
Affective disorders in multiple system atrophy: depression and anxiety, where SSRIs such as paroxetine are indicated.

Aside from MAO inhibitors, what drugs are dangerous to combine with SSRIs due to the risk of serotonin syndrome?

In addition to MAO inhibitors, sources point to a link between serotonin syndrome and:

MAO-B inhibitors in Parkinson's disease patients when combined with SSRIs;
Tramadol, for which a specific risk of serotonin syndrome due to excessive central serotonergic activity is described.

While a direct prohibition on combining SSRIs and tramadol may not always be explicitly formulated, the risk of serotonin syndrome with tramadol is established.

What contraindications exist for prescribing SSRIs besides concurrent MAO inhibitor use?

Aside from concurrent MAO inhibitor use, sources note specific restrictions for individual SSRIs:

Pregnancy: psychopharmacotherapy is avoided during pregnancy unless strictly necessary; when treatment is unavoidable, SSRIs are among the drugs of choice, strictly excluding paroxetine.
Tamoxifen therapy in breast cancer patients: paroxetine, fluoxetine, and sertraline should be avoided as they interfere with tamoxifen metabolism and reduce its efficacy.

Why are SSRIs better tolerated than tricyclic antidepressants?

Due to their selectivity, they have minimal or absent antimuscarinic action and show almost no affinity for alpha-adrenergic and histamine receptors, sparing patients from numerous side effects.

When does the antidepressant effect occur with paroxetine?

The antidepressant effect develops gradually with regular administration, with a latent period averaging 10 to 14 days.

What are the main manifestations of serotonin syndrome in overdose or dangerous combination?

The syndrome manifests with psychiatric disturbances (confusion, psychomotor agitation), as well as somatic and neurological disorders (muscle rigidity, hyperthermia, collapse).

Why is a "washout" period necessary when switching from MAO inhibitors to SSRIs?

An interval of at least 2 weeks is necessary to prevent a critical spike in synaptic serotonin concentration and the development of severe serotonin syndrome.

Go deeper

Comparative receptor profile of SSRIs and tricyclic antidepressants
Pharmacokinetic features of first-pass hepatic metabolism of paroxetine
Differences in the pharmacological effects of fluvoxamine and sertraline
Pathogenesis and clinical presentation of serotonin syndrome
Rules and duration of the washout period when switching antidepressant therapy