Excessive doses of escitalopram usually cause relatively minor untoward effects, such as agitation and tachycardia. However, dyskinesia, hypertonia, and clonus may occur in some cases. Therapeutic blood levels of escitalopram are usually in the range of 20–80 μg/L but may reach 80–200 μg/L in the elderly, patients with hepatic dysfunction, those who are poor CYP2C19 metabolizers or following acute overdose. Monitoring of the drug in plasma or serum is generally accomplished using chromatographic methods. Chiral techniques are available to distinguish escitalopram from its racemate, citalopram.