Citalopram

Citalopram is an antidepressant of the selective serotonin reuptake inhibitor (SSRI) class. It is used to treat major depressive disorder, obsessive-compulsive disorder, panic disorder, and social phobia. The antidepressant effect may have a latency of up to 4 weeks. It is taken by mouth and requires a prescription.

Pharmacodynamics

The mechanism of action of citalopram is based on its inhibition of neuronal reuptake of serotonin (5-HT) in the CNS. The molecular target of citalopram is the serotonin transporter (solute carrier family 6 member 4, SLC6A4), whose serotonin reuptake in the synaptic cleft is inhibited. As a result, the extracellular serotonin concentration increases permanently, thus enhancing and prolonging the mood-lifting effect of serotonin.

Pharmacokinetics

Citalopram is rapidly and well absorbed from the GI tract. Maximal plasma concentrations occur within 4 hours after a single oral dose. Bioavailability is 80% after oral administration. Citalopram is 80% bound to plasma proteins. Citalopram is metabolized primarily in the liver via N-demethylation to its major metabolite, demethylcitalopram, by the two enzymes CYP2C19 and CYP3A4. Excretion is via the urine and the mean elimination time is 35 hours.

Drug Interactions

Citalopram should not be combined with other antidepressants (especially MAO inhibitors). In addition, concomitant use of drugs that are degraded by or induce the same enzymes (CYP2C19 and CYP3A4) should be avoided.

Side effects

Common side effects include nausea, sleep disturbances, sexual problems, shakiness, fatigue, and sweating.

Serious side effects include increased risk of suicide in people under 25 years of age, serotonin syndrome, glaucoma, and QT prolongation. It should not be used in individuals taking an MAO inhibitor.

Side effects and withdrawal symptoms may occur when discontinuing the antidepressant.

It is not recommended for use during pregnancy or lactation.

Toxicological data

LD50 (human, oral): 56 mg/kg