Am J Psychiatry 1978; 135:557-561
Copyright © 1978 by American Psychiatric Association
Plasma and erythrocyte levels of tricyclic antidepressants in depressed patients
M Linnoila, F Dorrity Jr and K Jobson
Plasma and red blood cells (RBCs), amitriptyline, nortriptyline,
imipramine, desipramine, doxepin, and desmethyl doxepin levels were
measured in depressed inpatients during steady-state kinetics. A strong
positive correlation between the drug levels in plasma and RBCs was found
for amitriptyline, nortriptyline, desipramine, and desmethyl doxepin.
However, at a given plasma level, up to a 6-fold interindividual variation
in the RBC drug levels was found. The correlations between plasma and RBC
imipramine and doxepin levels were low. The interindividual variation in
the RBC-plasma tricyclic level ratios was large enough to warrant further
clinical studies on the relationship between efficacy and pharmacokinetics
of tricyclic antidepressants.
