Monitoring nortriptyline concentration during therapy
Evaluating potential nortriptyline toxicity
May aid in evaluating patient compliance
Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)
Aventyl
Nortriptyline, Serum
Pamelor
Sensoval
Norpress
Allegron
Nortrilen
TCA (Tricyclic Antidepressants)
Tricyclic Antidepressants (TCA)
Serum Red
Supplies: Sarstedt Aliquot Tube, 5 mL (T914)
Collection Container/Tube: Red top (Serum gel/SST are not acceptable)
Submission Container/Tube: Plastic vial
Specimen Volume: 1 mL
Collection Instructions:
1. Collect specimen immediately before next scheduled dose (minimum 12 hours after last dose).
2. Centrifuge and aliquot serum into a plastic vial. Serum must be separated from cells within 2 hours of collection.
If not ordering electronically, complete, print, and send a Therapeutics Test Request (T831) with the specimen.
0.25 mL
Gross hemolysis | Reject |
Gross lipemia | Reject |
Gross icterus | Reject |
Specimen Type | Temperature | Time | Special Container |
---|---|---|---|
Serum Red | Refrigerated (preferred) | 28 days | |
Frozen | 28 days | ||
Ambient | 7 days |
Monitoring nortriptyline concentration during therapy
Evaluating potential nortriptyline toxicity
May aid in evaluating patient compliance
Nortriptyline is a tricyclic antidepressant used for treatment of endogenous depression. It also is a metabolite of the antidepressant amitriptyline. Nortriptyline is used when its stimulatory side effect is considered to be of clinical advantage; amitriptyline is used when the side effect of mild sedation is desirable.
Nortriptyline is unique among the antidepressants in that its blood level exhibits the classical therapeutic window effect, as blood concentrations above or below the therapeutic window correlate with poor clinical response. Thus, therapeutic monitoring to ensure that the blood level is within the therapeutic window is critical to accomplish successful treatment with this drug.
Like amitriptyline, nortriptyline can cause major cardiac toxicity when the concentration is above 500 ng/mL, characterized by QRS widening (intraventricular conduction delay), which leads to ventricular tachycardia and asystole. In some patients, toxicity may manifest at lower concentrations.
Therapeutic concentration: 70-170 ng/mL
Note: Therapeutic ranges are for specimens collected at trough (ie, immediately before next scheduled dose). Levels may be elevated in non-trough specimens.
Most individuals display optimal response to nortriptyline with serum levels of 70 to 170 ng/mL. Risk of toxicity is increased with nortriptyline levels above 500 ng/mL.
Some individuals may respond well outside of this range or may display toxicity within the therapeutic range; thus, interpretation should include clinical evaluation.
Therapeutic ranges are based on specimens collected at trough (ie, immediately before the next dose).
This test cannot be performed on whole blood. Serum must be separated from cells within 2 hours of collection; if serum is not removed within this time, tricyclic antidepressant levels may be falsely elevated due to drug release from red blood cells.
Specimens that are obtained from gel tubes are not acceptable because the drug can absorb on the gel and lead to falsely decreased concentrations.
1. Wille SM, Cooreman SG, Neels HM, Lambert WE. Relevant issues in the monitoring and the toxicology of antidepressants. Crit Rev Clin Lab Sci. 2008;45(1):25-89
2. Thanacoody HK, Thomas SHL. Antidepressant poisoning. Clin Med (Lond). 2003;3(2):114-118
3. Hiemke C, Bergemann N, Clement HW, et al. Consensus guidelines for therapeutic drug monitoring in neuropsychopharmacology: Update 2017. Pharmacopsychiatry. 2018;51(1-01):9-62
4. Milone MC, Shaw LM. Therapeutic drugs and their management. In: Rifai N, Chiu RWK, Young I, Burnham CAD, Wittwer CT, eds. Tietz Textbook of Laboratory Medicine. 7th ed. Elsevier; 2023:420-453
Tuesday, Thursday, Sunday
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.
80299
Test Id | Test Order Name | Order LOINC Value |
---|---|---|
NOTRP | Nortriptyline, S | 3872-9 |
Result Id | Test Result Name |
Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
---|---|---|
37119 | Nortriptyline, S | 3872-9 |