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HelpTest Code DXPIN Doxepin and Nordoxepin, Serum
Reporting Name
Doxepin and Nordoxepin, SUseful For
Monitoring doxepin therapy
Evaluating potential doxepin toxicity
Evaluating patient compliance
Method Name
Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
Serum RedSpecimen Required
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.
Specimen Minimum Volume
0.25 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum Red | Refrigerated (preferred) | 28 days | |
| Frozen | 28 days | ||
| Ambient | 7 days |
Reject Due To
| Gross hemolysis | Reject |
| Gross lipemia | Reject |
| Gross icterus | Reject |
Reference Values
Therapeutic concentration (doxepin + nordoxepin): 50-150 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.
Day(s) Performed
Monday, Wednesday, Friday
CPT Code Information
80299
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| DXPIN | Doxepin and Nordoxepin, S | 43122-1 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 63507 | Doxepin | 3579-0 |
| 37125 | Nordoxepin | 3862-0 |
| 37126 | Doxepin and Nordoxepin | 3582-4 |
Clinical Information
Doxepin is recommended for the treatment of psychoneurotic patients with depression or anxiety, or with 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 more than 500 ng/mL. Other side effects include nausea, hypotension, and dry mouth.
Specimen Retention Time
14 daysReport Available
3 to 5 daysTest Classification
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.Forms
If not ordering electronically, complete, print, and send a Therapeutics Test Request (T831) with the specimen.