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HelpTest ID NOTRP Nortriptyline, Serum
Useful For
Monitoring serum concentration during therapy
Evaluating potential toxicity
The test may also be useful to evaluate patient compliance
Method Name
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
Reporting Name
Nortriptyline, SSpecimen Type
Serum RedContainer/Tube: Red top
Specimen Volume: 1 mL
Collection Instructions:
1. Draw specimen immediately before next scheduled dose (minimum 12 hours after last dose).
2. Serum must be separated from cells within 2 hours of draw.
Specimen Minimum Volume
0.25 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Serum Red | Refrigerated (preferred) | 28 days |
| Frozen | 28 days | |
| Ambient | 7 days |
Clinical Information
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; 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 ≥300 ng/mL, characterized by QRS widening leading to ventricular tachycardia and asystole. In some patients, toxicity may manifest at lower concentrations.
Reference Values
Therapeutic concentration: 70-170 ng/mL
Note: Therapeutic ranges are for specimens drawn at trough (ie, immediately before next scheduled dose). Levels may be elevated in non-trough specimens.
Cautions
This test cannot be performed on whole blood. Serum must be separated from cells within 2 hours of drawing; if serum is not removed within this time, tricyclic antidepressant levels may be falsely elevated due to drug release from RBCs. Specimens that are obtained from gel tubes are also not acceptable, as the drug can absorb on the gel and lead to falsely decreased concentrations.
Day(s) Performed
Monday through Friday; Varies
Report Available
2 daysPerforming Laboratory
Mayo Medical Laboratories in Rochester
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.CPT Code Information
80335
G0480 (if appropriate)