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Test ID DXPIN Doxepin and Nordoxepin, Serum

Useful For

Monitoring therapy

 

Evaluating potential toxicity

 

Evaluating patient compliance

Method Name

Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)

Reporting Name

Doxepin and Nordoxepin, S

Specimen Type

Serum Red

Container/Tube: Red top

Specimen Volume: 1 mL

Collection Instructions:

1. Draw specimen immediately before next scheduled dose (or at a 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

Doxepin is recommended for the treatment of psychoneurotic patients with depression or anxiety, and depression or anxiety associated with alcoholism or organic disease.

 

Nordoxepin (N-desmethyldoxepin) is the major metabolite and is usually present at concentrations equal to doxepin. Optimal efficacy occurs at combined serum concentrations between 50 and 150 ng/mL.

 

Like other tricyclic antidepressants, the major toxicity of doxepin is expressed as cardiac dysrhythmias, which occur at concentrations in excess of 300 ng/mL. Other side effects include nausea, hypotension, and dry mouth.

Reference Values

Therapeutic concentration (doxepin + nordoxepin): 50-150 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 Saturday; Varies

Report Available

2 days

Performing 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)

NY State Approved

Yes