Description

Citalopram, typically formulated as Citalopram Oxalate, is an antidepressant medication that belongs to a class of drugs called Selective Serotonin Reuptake Inhibitors (SSRIs). It is a racemic compound, meaning it contains two mirror-image forms (enantiomers), designated as S-citalopram and R-citalopram. A more potent version, escitalopram, is a single-enantiomer drug containing only the S-enantiomer. Citalopram is known for its high selectivity for the serotonin transporter and has a relatively mild side-effect profile compared to older antidepressants.

Indications

Citalopram is primarily used for the treatment of mental health conditions related to an imbalance in brain chemistry. Its main indications include:

• Major Depressive Disorder (MDD): Citalopram is FDA-approved for the treatment of depression in adults.

• Off-label Uses: It is also used off-label to treat various other conditions, including:
  • Obsessive-Compulsive Disorder (OCD)

• • Panic Disorder
  • Social Anxiety Disorder

• • Post-Traumatic Stress Disorder (PTSD)

• • Premenstrual Dysphoric Disorder (PMDD)

• • Generalized Anxiety Disorder (GAD)

Like other antidepressants, the full therapeutic effect of citalopram may take several weeks to become apparent.

Mechanism of Action

Citalopram’s mechanism of action is centered on its ability to increase the concentration of serotonin in the brain.

1. Serotonin System: Serotonin (5-HT) is a key neurotransmitter that plays a crucial role in regulating mood, emotion, sleep, and appetite. After a serotonin molecule is released into the synaptic cleft (the space between two neurons), it transmits a signal to the receiving neuron. To end the signal, the serotonin is typically reabsorbed by the releasing neuron via a protein called the serotonin transporter (SERT).

2. Citalopram’s Action: As a Selective Serotonin Reuptake Inhibitor, citalopram works by blocking the SERT. By binding to and inhibiting this transporter, citalopram prevents the reabsorption of serotonin back into the presynaptic neuron.

3. Resulting Effect: This inhibition leads to an increase in the concentration of serotonin in the synaptic cleft. The elevated serotonin levels allow the neurotransmitter to bind more frequently to the receptors on the postsynaptic neuron, enhancing serotonergic activity and improving communication between neurons. Over time, this sustained increase in serotonin is thought to lead to adaptive changes in the brain that are responsible for the drug’s antidepressant and anxiolytic effects.

A key feature of citalopram is its high selectivity for the serotonin transporter. It has very little to no effect on other neurotransmitter systems, such as dopamine, norepinephrine, acetylcholine, or histamine. This selectivity is what contributes to its favorable side effect profile compared to older antidepressant classes.