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22571 Doxepin and Nordoxepin (DXPIN)

Doxepin and Nordoxepin (DXPIN)
Test Code: DOXSO
Synonyms/Keywords
Adapin (Doxepin), Doxepin (Sinequan), Nordox (Doxepin)
Useful For
Monitoring doxepin therapy
Evaluating potential doxepin toxicity
Evaluating 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 reject
​Lipemia
Gross reject
​Icterus
Gross reject
​Other ​Serum gel tube
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​​
Monday, Wednesday, Friday 
 2 to 5 days Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
Reference Lab
Mayo Clinic Laboratories
Reference Range Information
Performing Location Reference Range
Mayo Clinic Laboratories​​
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.
Interpretation
Most individuals display optimal response to doxepin when combined serum levels of doxepin and nordoxepin are between 50 and 150 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. Risk of toxicity is increased with combined levels > or =300 ng/mL.
 
Therapeutic ranges are based on specimens drawn at trough (ie, immediately before the next dose).
Outreach CPTs
CPT Modifier
(if needed)		 Quantity Description Comments
​80299​
 ​ ​ ​ ​
Synonyms/Keywords
Adapin (Doxepin), Doxepin (Sinequan), Nordox (Doxepin)
Ordering Applications
Ordering Application Description
​Centricity ​LAB Doxepin and Nordoxepin (DOXP)
​Cerner ​Doxepin and Nordoxepin Level (DOXP)
If the ordering application you are looking for is not listed, contact your local laboratory for assistance.
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
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 reject
​Lipemia
Gross reject
​Icterus
Gross reject
​Other ​Serum gel tube
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.

Useful For
Monitoring doxepin therapy
Evaluating potential doxepin toxicity
Evaluating patient compliance
Reference Range Information
Performing Location Reference Range
Mayo Clinic Laboratories​​
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.
Interpretation
Most individuals display optimal response to doxepin when combined serum levels of doxepin and nordoxepin are between 50 and 150 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. Risk of toxicity is increased with combined levels > or =300 ng/mL.
 
Therapeutic ranges are based on specimens drawn at trough (ie, immediately before the next dose).
For more information visit:
Performing Laboratory Information
Performing Location Day(s) Test Performed Report Available Methodology/Instrumentation
Mayo Clinic Laboratories​​
Monday, Wednesday, Friday 
 2 to 5 days Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
Reference Lab
Mayo Clinic Laboratories
For billing questions, see Contacts
Outreach CPTs
CPT Modifier
(if needed)		 Quantity Description Comments
​80299​
 ​ ​ ​ ​
For most current information refer to the Marshfield Laboratory online reference manual.