INTRODUCTION: The effect of aging on steady-state plasma concentrations of paroxetine was investigated in 136 depressive patients treated with paroxetine 10-120 mg/day. METHODS: The patients were divided into three groups: aged up to 64 years (mean age ± standard deviation: 41.7±12.6 years; n = 44), between 65 and 79 years (72.8±4.7 years; n = 64), and 80 years or older (82.8±3.3 years; n = 28). Paroxetine doses were normalized to 20 mg/day. Blood samples were collected under steady-state conditions. Paroxetine plasma levels were measured by gas chromatography/mass spectrometry. Hepatic and renal functions were measured by standardized clinical laboratory tests. RESULTS: A large interindividual variability of paroxetine plasma levels (37-fold) was measured for a given dose. The mean plasma levels of paroxetine corrected for a 20 mg daily dose were 87% higher in the very elderly (≥ 80 years) patients (56.4±64.1 ng/mL; p < 0.05) and 57% higher in the elderly (65-79 years) patients (46.7±33.4 ng/mL; p < 0.001) when compared to the adult patients (< 64 years) (29.9±11.9ng/mL). Age correlated significantly with paroxetine plasma levels (r = 0.21, p < 0.05). CONCLUSION: Recommended dose reduction of paroxetine in elderly patients seems therefore justified.
Paroxetine; elderly; depression; plasma levels; antidepressants
