Pharmacology: Antidepressants, selective serotonin reuptake inhibitors.
Pharmacodynamics: Escitalopram is the S-enantiomer of the racemic derivative citalopram, which selectively inhibits the reuptake of serotonin with little to no effect on norepinephrine or dopamine reuptake. It has no or very low affinity for 5-HT1-7, alpha- and beta-adrenergic, D1-5, H1-3, M1-5, and benzodiazepine receptors. Escitalopram does not bind to or has low affinity for Na+, K+, Cl-, and Ca++ ion channels.
Pharmacokinetics: Onset of action: Depression: The onset of action is within a week; however, individual response varies greatly and full response may not be seen until 8-12 weeks after initiation of treatment.
Distribution: 20 L/kg.
Protein binding: 56% to plasma proteins.
Metabolism: Hepatic via CYP2C19 and 3A4 to S-desmethylcitalopram (S-DCT); S-DCT is metabolized to S-didesmethylcitalopram (S-DDCT) via CYP2D6; in vitro data suggest metabolites do not contribute significantly to the antidepressant effects of escitalopram.
Half-life elimination: 27-32 hours (increased 50% in the elderly and doubled in patients with hepatic impairment).
Time to peak: Escitalopram 5 hours.
Excretion: Urine.