Correlations between serum ami- and nortriptyline concentrations and psychomotor performance

Area of Science:

• Pharmacology
• Neuroscience
• Clinical Psychology

Background:

• Tricyclic antidepressants like nortriptyline (NT) and amitriptyline (AT) are widely prescribed.
• Understanding their impact on cognitive and psychomotor functions is crucial for patient management.
• Previous research has yielded mixed results regarding the relationship between antidepressant levels and performance.

Purpose of the Study:

• To examine the correlation between serum levels of nortriptyline (NT) and amitriptyline (AT) and psychomotor performance in healthy subjects.
• To assess the impact of these antidepressants on choice reaction time, eye-hand coordination, and divided attention.
• To present a novel assay method for quantifying AT and NT levels.

Main Methods:

• Two experiments were conducted with 20 healthy subjects each.
• Experiment 1: Serum NT levels measured via isotope derivative method after 14-day NT treatment.
• Experiment 2: Plasma AT and NT concentrations measured using gas-chromatography after 14-day AT treatment.

Main Results:

• No significant linear correlations were observed between serum antidepressant levels and psychomotor performance variables.
• Low serum NT levels (<50 ng/ml) showed a trend towards shortening reaction time compared to placebo.
• Intermediate NT levels (50–80 ng/ml) tended to prolong reaction time.
• The correlation between serum NT levels and tyramine pressor test response was not statistically significant.

Conclusions:

• Serum concentrations of nortriptyline and amitriptyline do not linearly correlate with psychomotor performance in healthy individuals.
• Specific serum NT levels may influence reaction time, with low levels potentially speeding it up and intermediate levels slowing it down.
• The study introduces a new assay method for AT and NT, contributing to improved analytical techniques in psychopharmacology.