Chapter 14.Citalopram and Escitalopram

Citalopram (Celexa) and its pharmacologically active enantiomer, escitalopram (Lexapro), are among the most selective serotonin reuptake inhibitors available. Both drugs are widely prescribed and have been shown in large-scale controlled trials to be effective in the treatment of depression; escitalopram has also been shown to be effective in the treatment of anxiety disorders. Generic formulations of both drugs are now available. Both drugs are well tolerated in patients and show a low potential for pharmacokinetic drug–drug interactions. Citalopram and escitalopram have similar effectiveness in the treatment of depression, although some studies suggest a modest superiority of escitalopram over citalopram on some measures of efficacy, including a possibly faster onset of therapeutic effect for escitalopram. Antagonism of the effects of escitalopram by R-citalopram has been invoked to explain the purported therapeutic differences between the two drugs. Also, the affinity of citalopram for histamine receptors appears to reside in the R-enantiomer, suggesting that escitalopram has a decreased potential for antihistaminergic side effects. Finally, in terms of cardiac safety, citalopram has a greater potential to prolong the electrocardiogram (ECG) QT interval and produce potentially serious arrhythmias.