Objective: The authors' goal was to compare serum anticholinergicity of 61 elderly depressed patients randomly assigned to double-blind treatment with paroxetine (N=31) or nortriptyline (N=30).
Method: Both antidepressants were titrated in a standardized manner, and plasma was sampled weekly for measurement of paroxetine and nortriptyline and its hydroxy metabolite concentrations. Serum anticholinergicity was measured at baseline and after 1, 4, and 6 weeks of treatment. Side effects were assessed by using a validated scale.
Results: After correcting for pretreatment anticholinergicity, the authors found that mean serum anticholinergicity for the nortriptyline-treated patients was significantly greater than that for the paroxetine group at all weeks assessed. Serum anticholinergicity was significantly correlated with nortriptyline but not with paroxetine plasma levels. Complaints of dry mouth and tachycardia were significantly more frequent and severe in the nortriptyline group.
Conclusions: These findings suggest that, at therapeutic plasma concentrations, paroxetine has approximately one-fifth the anticholinergic potential of nortriptyline in older patients.