Description

Citalopram, typically formulated as Citalopram Hydrobromide (HBr), is an antidepressant medication belonging to the class of Selective Serotonin Reuptake Inhibitors (SSRIs). It is a racemic compound, meaning it is a mixture of two mirror-image forms (enantiomers), the R- and S-enantiomers. The S-enantiomer, known as escitalopram, is the pharmacologically active component responsible for its therapeutic effects. Citalopram HBr is known for its high selectivity for the serotonin transporter and has a well-established safety profile.

Indications

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

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

It is also commonly used off-label to treat various other conditions, including:

• Obsessive-Compulsive Disorder (OCD)

• Panic Disorder

• Premenstrual Dysphoric Disorder (PMDD)

• Generalized Anxiety Disorder (GAD)

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 and for a longer duration 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, or histamine, which contributes to its favorable side-effect profile compared to older antidepressants. The difference between Citalopram HBr and Citalopram Oxalate is simply the salt form of the same active drug; they have the same description, indications, and mechanism of action.