Citalopram

Citalopram is an antidepressant in the selective serotonin reuptake inhibitor (SSRI) class. It is approved for the treatment of major depressive disorder and is sometimes used off-label for other anxiety disorders. It works by increasing serotonin levels in the synaptic cleft through inhibition of its reuptake into presynaptic neurons.

Pharmacology and pharmacokinetics: Citalopram is taken orally and has good bioavailability. The elimination half-life is about 35 hours, and it has an active metabolite called desmethylcitalopram. It is primarily metabolized in the liver by cytochrome P450 enzymes, especially CYP2C19, with contributions from CYP2D6 and CYP3A4, and is excreted in urine. Clinically relevant antidepressant effects typically emerge after several weeks of treatment.

Dosing and indications: A typical starting dose for adults is 20 mg once daily. Depending on response and tolerability, the dose may be increased to a maximum of 40 mg daily in many regions, though elderly patients or those with hepatic impairment may require lower doses. Dosing should consider the risk of QT interval prolongation, which can be greater at higher doses and in individuals with certain medical conditions or on interacting medications.

Safety and adverse effects: Common side effects include nausea, dry mouth, sleep disturbance or fatigue, sweating, and sexual dysfunction. Weight changes and gastrointestinal symptoms may occur. Discontinuation symptoms can arise after abrupt withdrawal. A key safety concern is QT interval prolongation, especially at higher doses or with electrolyte disturbances or concurrent QT-prolonging drugs; this risk guides dose limits and patient selection.

Interactions and precautions: Avoid coadministration with monoamine oxidase inhibitors and exercise caution with other serotonergic drugs and with drugs known to prolong the QT interval. Consider caution in hepatic impairment and in patients with cardiac conduction abnormalities.