Clinics and Departments

Laboratory Services

Lab Dept:


Test Name:


General Information

Lab Order Codes:



AventylŪ, PamelorŪ

CPT Codes:

80335 – Antidepressants, serotonergic class; 1 or 2

Test Includes:

Nortriptyline concentration reported in ng/mL.


Test Indications:

Therapeutic antidepressant monitoring, monitoring patient compliance, and detection of toxic concentration.

Lab Testing Sections:

Chemistry - Sendouts

Referred to:

Mayo Medical Laboratories (Test: NORT)

Phone Numbers:

MIN Lab: 612-813-6280

STP Lab: 651-220-6550

Test Availability:

Daily, 24 hours

Turnaround Time:

2 - 4 days, test set-up Monday – Saturday

Special Instructions:

It is recommended that blood be drawn 12 hours after the last dose. Gel tubes are not acceptable.


Specimen Type:



Red top tube

Draw Volume:

6 - 9 mL (Minimum: 3. 3 mL) blood

Processed Volume:

2 – 3 mL (Minimum: 1.1 mL) serum


Routine venipuncture

Special Processing:

Lab Staff: Centrifuge specimen, remove plasma aliquot into a screw-capped round bottom plastic vial. Store and ship at refrigerated temperatures. Forward promptly.

Patient Preparation:


Sample Rejection:

Hemolyzed specimens; mislabeled or unlabeled specimens


Reference Range:

70 – 170 ng/mL

Note: Therapeutic ranges are for specimens drawn at trough (i.e., immediately before the next scheduled dose). Levels may be elevated in non-trough specimens.

Critical Values:

Toxic: ≥300 ng/mL


Nortriptyline analytical interferences: Sertraline may cause falsely low results, metformin may cause false elevations.

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, TCA levels may be falsely elevated due to drug release from red blood cells. Specimens that are obtained from gel tubes are not acceptable.


High Performance Liquid Chromatography (HPLC)


Mayo Medical Laboratories Web Page October 2012


3/11/2004: Test moved from MedTox Laboratories to Mayo Medical Laboratories.
10/26/2009: Note: Reference value update. Plasma samples are no longer acceptable.
10/25/2012: Toxic level change, previously listed as > or =500 ng/mL.
1/7/2015: CPT update

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