Effect of age and gender on citalopram and desmethylcitalopram steady-state plasma concentrations in adults and elderly depressed patients

The effect of aging on steady-state plasma concentrations of citalopram (CIT) and desmethylcitalopram (DCIT) was investigated in 128 depressive patients treated with 10-80 mg/day CIT. They were separated into three groups, with age up to 64 years (mean age ± S.D.: 47 ± 12 years; n = 48), between 65 and 79 years (72 ± 1 years; n = 57), and from 80 years or older (84 ± 1 years; n = 23). Body mass index (BMI), renal and hepatic functions were similar in the three groups. A large interindividual variability of plasma levels of CIT (16-fold) and DCIT (12-fold) was measured for a given dose. The mean plasma levels of CIT corrected for a 20 mg daily dose were 55% higher in the very elderly (> = 80 years) patients (65 ± 30 ng/ml; p < 0.001) and 38% higher in the elderly (65-79 years) patients (58 ± 24 ng/ml; p < 0.001) when compared to the adult patients (42 ± 17 ng/ml). DCIT mean plasma level was 38% higher (p < 0.05) in the group of very elderly patients (22 ± 10 ng/ml) when compared to the adult patients (16 ± 9 ng/ml). As a consequence, the mean plasma concentration of CIT + DCIT was 48% higher in the very elderly patients (86 ± 36 ng/ml; p < 0.001) and 33% higher in the elderly patients (77 ± 28 ng/ml; p < 0.001) when compared to the adult patients (58 ± 21 ng/ml). Age correlated significantly with CIT (r = 0.43, p < 0.001), DCIT (r = 0.28, p < 0.01), and CIT + DCIT plasma levels (r = 0.44, p < 0.001), and thus accounts for 18% of the variability of CIT plasma levels, with no influence of gender. The recommended dose reduction of CIT in elderly patients seems therefore justified.