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HelpTest Code FENTS Fentanyl, Serum
Reporting Name
Fentanyl and Metabolites, SUseful For
Monitoring fentanyl therapy
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: 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 | Special Container |
|---|---|---|---|
| Serum Red | Frozen (preferred) | 28 days | |
| Refrigerated | 14 days | ||
| Ambient | 72 hours |
Reject Due To
| Gross hemolysis | OK |
| Gross lipemia | OK |
| Gross icterus | OK |
Reference Values
Not applicable
Day(s) Performed
Tuesday, Thursday
CPT Code Information
80354
G0480 (if appropriate)
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 |
Clinical Information
Fentanyl is an extremely fast-acting synthetic opioid related to the phenylpiperidines.(1,2) It is available in injectable as well as transdermal formulations.(1) The analgesic effects of fentanyl are similar to those of morphine and other opioids(1), as it interacts predominantly with the opioid mu-receptor. These mu-binding sites are discretely distributed in the human brain, spinal cord, and other tissues.(1,3)
Fentanyl is approximately 80% to 85% protein bound.(1) Fentanyl plasma protein-binding capacity decreases with increasing ionization of the drug. Alterations in pH may affect its distribution between plasma and the central nervous system (CNS). The average volume of distribution for fentanyl is 6 L/kg (range 3-8).(3,4)
In humans, the drug appears to be metabolized primarily by oxidative N-dealkylation to norfentanyl and other inactive metabolites that do not contribute materially to the observed activity of the drug. Within 72 hours of intravenous (IV) administration, approximately 75% of the dose is excreted in urine, mostly as metabolites with less than 10% representing unchanged drug.(3,4)
The mean elimination half-life is:(1-3)
-IV: 2 to 4 hours
-Iontophoretic transdermal system (Ionsys), terminal half-life: 16 hours
-Transdermal patch: 17 hours (range 13-22 hours, half-life is influenced by absorption rate)
-Transmucosal:
-Lozenge: 7 hours
-Buccal tablet
-100 to 200 mcg: 3 to 4 hours
-400 to 800 mcg: 11 to 12 hours
In clinical settings, fentanyl exerts its principal pharmacologic effects on the CNS. In addition to analgesia, alterations in mood (euphoria, dysphoria) and drowsiness commonly occur.(1,3) Because the biological effects of fentanyl are similar to those of heroin and other opioids, fentanyl has become a popular drug of abuse.
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.
Cautions
Specimens collected in serum gel tubes are not acceptable because the drug can absorb on the gel and lead to falsely decreased concentrations.
Method Description
Fentanyl is isolated from serum using a liquid/liquid extraction. The solvent is dried, and the analytes are reconstituted with mobile phase. Analysis is performed by liquid chromatography tandem mass spectrometry using selected ion monitoring.(Unpublished Mayo method)