Plasma ratio trytophan/neutral amino acids in relation to clinical response to paroxetine and clomipramine in patients with major depression

Plasma Tryptophan to Large Neutral Amino Acids Ratio and Therapeutic Response to a Selective Serotonin Uptake Inhibitor

“…This result suggests that clinical response may be explained by differential pharmacodynamic properties rather than by pharmacokinetic variables. Althoug plasma fluvoxamine levels were not the main focus of the present work, our results agree with those found in the literature [4], even if we cannot consider them conclusive.…”

“…For this reason we expected to find a better clinical response in subjects with a low Trp/LNAAs ratio, accord ing to the data reported in the literature [4,5], Our results show that the good responders to the 5-HT uptake inhibitor had a lower pre-treatment plasma Trp/ LNAAs ratio than non-responders to the same therapy, suggesting that this biological paramter may be a useful tool for increasing the efficacy of antidepressant treat ment. In fact, these data may support the hypothesis that a low Trp/LNAAs ratio might be a predictive index of good response to antidepressant treatment with molecules potentiating serotonergic neurotransmission.…”

“…Our results suggested the impor tance of the Trp/LNAAs ratio in relation to the presenceabsence of depressive symptoms, in agreement with other similar studies [8][9][10][11][12][13], We also tested the usual clinical variables of depression and they did not show any correla tion with this biological parameter. As suggested by pre- vious studies [4][5][6], the Trp/LNAAs ratio may become a useful biological tool when correlated to pharmacological response.…”

“…Data from the literature suggest the use of plasma amino acid profile as a biological mark er for clinical improvement on a variety of antidepressant treatments. Results are intriguing, as they report a signifi cant inverse correlation between Trp plasma levels or the Trp/LNAAs ratio and clinical improvement on serotoner gic antidepressants (both tricyclics and selective 5-HT uptake inhibitors) and no correlation on the monoamino oxidase inhibitor moclobemide [4][5][6],…”

Demonstration of the Efficacy and Safety of a Novel Substance P (NK1) Receptor Antagonist in Major Depression

“…Subsequent literature (eg Arora and Meltzer, 1989;Deakin et al, 1990;Delgado et al, 1989;Maes et al, 1990;Meltzer and Lowy, 1987;Mller et al, 1990;Sarrias et al, 1987;Upadhyaya et al, 1991;Young et al, 1985) suggested that serotonergic mechanisms may in part underlie vulnerability to major depression (and some anxiety disorders), and that agents that increase serotonergic activity may be therapeutic. Functional underactivity in dopamine transmission has also been comparatively recently suggested (Randrup et al, 1975;Willner, 1983) to contribute to the pathology of depression.…”