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UW Health SMPH
American Family Children's Hospital

UW Hospital and Clinics Lab Test Directory

Test Name: Doxepin

Test Code(s): DOX / HCDOX

CPT Code(s): 80335

Test Description: Test Component:

Doxepin and metabolite desmethyldoxepin

Methodology: Liquid Chromatography

Clinical Significance: Antidepressant

Days Performed: Daily, dayshift.

Turnaround Time: Routine: 24 hours.

Specimen Requirements

Specimen: Blood

Collection Instructions: Collect specimen for trough level prior to next dose.

Collection Container: Preferred: Red top

Collection Volume: Preferred: 4 mL
Pediatrics: 4 mL

Sample Analyzed: Serum

Volume Required: Preferred: 2 mL
Pediatrics: 1.5 mL

Specimen Processing: Centrifuge. Transfer cell-free serum to plastic vial. Refrigerate.

Specimen Transport: Transport specimen to UWHC Core Laboratory (B4/220). Transport with coolant pack if coming from outreach location.

Unacceptable Criteria: Specimens collected in red cap with yellow ring (SST) tubes are not acceptable.

Stability: Ambient: 5 days
Refrigerated: 7 days
Frozen: 1 year


Interpretive Guidelines:
Generally effective therapeutic concentration: 
18 years and up:

doxepin plus

desmethyldoxepin: 150-250 ng/mL

18 years and up:

Total concentration of doxepin

and desmethyldoxepin >500 ng/mL


Critical Calls: View

Additional Information:

Result of "BELOW" indicates that the result is below the method detection limit of 10 ng/mL. The half-life of doxepin in an adult is 12-23 hours.


This test was developed and its performance characteristics determined by the UWHC Clinical Laboratories.  This test meets the standards for clinical testing.  This test should not be regarded as investigational or for research use.  The US Food and Drug Administration (FDA) has not approved or cleared this test; however, the FDA has determined that such clearance or approval is not necessary.


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