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Test Code FENTS Fentanyl, Serum

Reporting Name

Fentanyl and Metabolites, S

Useful For

Monitoring fentanyl therapy

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Serum Red


Specimen 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: 2.3 mL

Collection Instructions: Within 2 hours of collection, centrifuge and aliquot serum into a plastic vial.


Specimen Minimum Volume

1.25 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Red Frozen (preferred) 28 days
  Refrigerated  14 days
  Ambient  72 hours

Reference Values

Fentanyl:

Average serum fentanyl concentrations 24 hours after application of transdermal patch:

25 mcg/hour: 0.3-1.2 ng/mL

50 mcg/hour: 0.6-1.8 ng/mL

75 mcg/hour: 1.1-2.6 ng/mL

100 mcg/hour: 1.9-3.8 ng/mL

(Baselt RC. Disposition of Toxic Drugs and Chemical in Man. 12th ed. Biomedical Publications; 2020)

 

Norfentanyl:

Reference range: Not established

 

Cutoff concentrations by liquid chromatography tandem mass spectrometry:

Fentanyl: 0.05 ng/mL

Norfentanyl: 0.25 ng/mL

Day(s) Performed

Tuesday, Thursday

Test 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.

CPT Code Information

G0480

80354 (if appropriate for select payers)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
FENTS Fentanyl and Metabolites, S 81275-0

 

Result ID Test Result Name Result LOINC Value
31829 Norfentanyl 11074-2
31830 Fentanyl 3636-8
31832 Chain of Custody 77202-0

Interpretation

Both fentanyl and norfentanyl are reported.

 

Tolerant individuals may require many-fold increases in dose to achieve the same level of analgesia, which can greatly complicate interpretation of therapeutic drug monitoring results and establishment of a therapeutic window.

 

Concentration at which toxicity occurs varies and should be interpreted in light of clinical situation.

Clinical Reference

1. Gutstein HB, Akil H. Opioid analgesics. In: Brunton LL, Lazo JS, Parker KL, eds. Goodman and Gilman's: The Pharmacological Basis of Therapeutics. 11th ed. McGraw-Hill Companies; 2006:chap 21

2. Kerrigan S, Goldberger BA. Opioids. In: Levine B, eds. Principles of Forensic Toxicology. 2nd ed. AACC Press; 2003:187-205

3. DURAGESIC (fentanyl transdermal system). Package insert: Janssen Pharmaceutica Products, LP; 2006

4. Baselt RC. Disposition of Toxic Drugs and Chemicals in Man. 12th ed. Biomedical Publications; 2020

5. Yaksh T, Wallace M. Opioids, Analgesia, and Pain Management. In: Brunton LL, Hilal-Dandan R, Knollmann BC, eds. Goodman and Gilman's: The Pharmacological Basis of Therapeutics, 13th ed. McGraw-Hill Education; 2017

6. Langman LJ, Bechtel LK, Holstege CP. Clinical toxicology. In: Rifai N, Chiu RWK, Young I, Burnham CAD, Wittwer CT, eds. Tietz Textbook of Laboratory Medicine. 7th ed. Elsevier; 2023:chap 43

7. Fentanyl. In: Merative Micromedex (electronic version). Merative US 2024. Accessed April 7, 2025. Available at www.micromedexsolutions.com

Report Available

2 to 7 days

Method Name

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

Forms

If not ordering electronically, complete, print, and send a Therapeutics Test Request (T831) with the specimen.