Nortriptyline (NOTRP)

Test Code: NORTSO

Overview
Ordering
Specimen
Performing
Clinical/Interpretive
Contacts
Coding

Synonyms/Keywords

Aventyl (Nortriptyline), Serum, Nortriptyline, Serum, Pamelor (Nortriptyline), Serum, Sensoval, Aventyl, Pamelor, Norpress, Allegron, and Nortrilen (Nortriptyline), TCA (Tricyclic Antidepressants), Tricyclic Antidepressants (TCA)

Useful For

Monitoring serum concentration during therapy

Evaluating potential toxicity

The test may also be useful to evaluate patient compliance

Specimen Requirements

Specimen Type	Preferred Container/Tube	Acceptable Container/Tube	Specimen Volume	Specimen Minimum Volume (allows for 1 repeat)	Pediatric Minimum Volume (no repeat)
Serum	Red Top Tube (RTT)		1 mL	0.25 mL

Collection Processing 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 Stability Information

Specimen Type	Temperature	Time
Serum	Refrigerated (preferred)	28 days
	Ambient	7 days
	Frozen	28 days

Rejection Criteria

Hemolysis	Gross
Lipemia	Gross
Icterus	Gross
Serum Separator Tube (SST)

Interference

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.

Performing Laboratory Information

Performing Location	Day(s) Test Performed	Report Available	Methodology/Instrumentation
Mayo Clinic Laboratories	Tuesday, Thursday, Sunday	3 to 5 days	Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)

Reference Lab

Mayo Clinic Laboratories

Test 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 >500 ng/mL, characterized by QRS widening leading to ventricular tachycardia and asystole. In some patients, toxicity may manifest at lower concentrations.

Reference Range Information

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.

Interpretation

Most individuals display optimal response to nortriptyline with serum levels of 70 to 170 ng/mL. Risk of toxicity is increased with nortriptyline levels >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 drawn at trough (ie, immediately before the next dose).

Outreach CPTs

CPT	Modifier (if needed)	Quantity	Description	Comments
80335

Synonyms/Keywords

Ordering Applications

Ordering Application	Description
Cerner	Nortriptyline Level (NORT)

If the ordering application you are looking for is not listed, contact your local laboratory for assistance.