The pharmacokinetics of escitalopram after oral and intravenous administration of single and multiple doses to healthy subjects

The pharmacokinetics of escitalopram (S-citalopram) and its principal metabolite, S-demethylcitalopram (S-DCT), were investigated after intravenous and oral administration to healthy subjects. After intravenous infusion of escitalopram, the mean systemic clearance and volume of distribution were 31 L/h and 1100 L, respectively After oral administration Of single or multiple doses, the absorption was relatively fast, with the maximum observed plasma or serum concentration attained after 3 to 4 hours. The mean half-lives were 27 and 33 hours, respectively, steady state was attained within 10 days. The area under the plasma or serum concentration-time curve from time zero to 24 hours and C-max was both linear and proportional to the dose. The apparent volume of distribution was around 20 L/kg. Comparison of the systemic and oral clearance implied a high absolute bioavailability, There was no evidence of interconversion from S-citaloprom to R-citalopram either in plasm a or in urine. Concurrent in take of food had no effect on the pharmacokinetics of escitalopram or its metabolite. All treatments were well tolerated.