Does Citalopram cross the blood-brain barrier? (+3 factors)

In this article, we will answer whether Citalopram crosses the blood-brain barrier or not. We will further look into the common pathway of Citalopram as an SSRI antidepressant. We will also provide an overview of the factors affecting the penetration across the BBB.

Does Citalopram cross the blood-brain barrier?

Yes, Citalopram can cross the blood-brain barrier (BBB). Citalopram is an SSRI antidepressant and works by inhibiting the reuptake of serotonin in the brain, therefore, it can cross the BBB.

Citalopram, like other antidepressants, enters the brain and increases serotonin levels which helps in regulating mood and treating anxiety, depression, and other related conditions.

How does Citalopram penetrate the BBB?

Citalopram penetrates the blood-brain barrier (BBB) due to its chemical structure and mechanism of action among other SSRI antidepressants. It is a highly potent and selective SSRI drug (1).

Based on the chemical structure of this drug, Citalopram is a racemic drug and its therapeutic activity lies in the S-enantiomer whereas, the R-enantiomer is practically devoid of serotonin reuptake (1,2).

Depending upon the chemical structure, Citalopram does not directly affect the integrity of the BBB. But once it enters the brain, it acts on serotonin transporters,  improves mood regulation, and treats anxiety and depression-related conditions.

Neuropsychiatric drugs consist of drug-bound and unbound concentrations. Similar to other psychoactive drugs, Citalopram is also bound to plasma proteins. It is assumed that only the unbound fraction of Citalopram can passively cross the BBB (1).

The protein binding varies based on individual factors like metabolism, liver function, polypharmacy, etc. Therefore, Citalopram should be prescribed to patients after considering such factors.

However, it is suggested that Citalopram crosses the BBB via a non-stereoselective, bidirectional, and symmetrical carrier-mediated mechanism. This occurs without the influence of active efflux mechanisms (3).

Factors that affect the permeability of Citalopram across the BBB

Following are a few factors that affect the permeability of Citalopram across the BBB (1,3):

Molecular size and Active transport

The molecular size and structure of Citalopram greatly affect its ability to cross the BBB. Preferably, the smaller molecules of Citalopram are more likely to cross the BBB readily.

The serotonin transporters in the brain significantly play an important role in helping the Citalopram molecules to cross the BBB.

The high concentrations of Citalopram in the cerebrospinal fluid indicate an active transport of Citalopram into the brain. This results in higher drug concentration at target sites which contribute towards the clinical efficacy (1).

Protein binding and Lipophilicity

Protein binding is another important factor in the penetration of Citalopram across the BBB. Highly bound drugs have fewer unbound molecules to freely cross the BBB and exert their effects on the brain.

The lipophilicity or the ability of the drug molecules to dissolve in lipids is a plus point for Citalopram to cross the BBB. The lipophilic drugs tend to cross the BBB more readily as compared to the hydrophilic drugs.

How to ensure the safe use of Citalopram?

You can ensure safe and effective use of Citalopram by following the exact dosage strength and frequency of the drug prescribed by your health care provider. Do not change or miss the dosage recommended by the doctor.

Monitor your side effects regularly. It is essential to familiarize yourself with the potential side effects of Citalopram. If you face severe adverse effects, do not abruptly stop taking the medication or go cold turkey. Instead, consult your doctor for a dosage reduction or a medication switch.

Never miss your follow-up sessions with your doctor. Also, educate yourself about the potential drug interactions, adverse effects, and risks of taking psychotropic drugs such as Citalopram.

Avoid alcohol consumption along with Citalopram. It enhances the sedative side effects and also increases the potential risk factors. Therefore, it is advised to avoid alcohol and other intoxicants while being on Citalopram.


We have answered that Citalopram can cross the blood-brain barrier. We have successfully discussed the role of Citalopram in the brain and its capacity to penetrate the BBB to perform its function. We have also discussed the factors that affect the penetration of Citalopram across the BBB.

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Paulzen, M., Lammertz, S. E., Gründer, G., Veselinovic, T., Hiemke, C., & Tauber, S. C. (2016). Measuring citalopram in blood and central nervous system. International Clinical Psychopharmacology, 31(3), 119–126. doi: 10.1097/yic.0000000000000114


Sangkuhl K, Klein TE, Altman RB. PharmGKB summary: citalopram pharmacokinetics pathway. Pharmacogenet Genomics. 2011 Nov;21(11):769-72. doi: 10.1097/FPC.0b013e328346063f. PMID: 21546862; PMCID: PMC3349993.


Rochat B, Baumann P, Audus KL. Transport mechanisms for the antidepressant citalopram in brain microvessel endothelium. Brain Res. 1999 Jun 12;831(1-2):229-36. doi: 10.1016/s0006-8993(99)01461-4. PMID: 10412001.

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