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HelpTest ID PARO Paroxetine, Serum
Specimen Required
Collection Container/Tube: Red top (serum gel/SST are not acceptable)
Submission Container/Tube: Plastic vial
Specimen Volume: 0.5 mL
Collection Instructions:
1. Draw blood before next scheduled dose.
2. Centrifuge and aliquot serum into plastic vial within 2 hours of collection.
Forms
If not ordering electronically, complete, print, and send a Therapeutics Test Request (T831) with the specimen.
Secondary ID
83731Useful For
Monitoring paroxetine therapy
Identifying noncompliance, although regular blood level monitoring is not indicated in most patients
Identifying states of altered drug metabolism when used in conjunction with CYP2D6 genotyping
Method Name
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
Reporting Name
Paroxetine, SSpecimen Type
Serum RedSpecimen Minimum Volume
0.4 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | |
|---|---|---|---|
| Serum Red | Refrigerated (preferred) | 28 days | |
| Ambient | 28 days | ||
| Frozen | 28 days |
Clinical Information
Paroxetine (Paxil and Paxil CR) is approved for treatment of depression. Paroxetine is completely absorbed. Metabolites of paroxetine are inactive. Paroxetine metabolism is carried out by cytochrome P450 (CYP) 2D6. Paroxetine can saturate CYP2D6 resulting in a nonlinear relationship between dose and serum concentration. Paroxetine clearance is significantly affected by reduced hepatic function but only slightly by reduced kidney function.
A typical adult paroxetine dose is 20 mg per day. Paroxetine is 100% bioavailable, 95% protein bound, and the apparent volume of distribution is 17 L/kg. Time to peak serum concentration is 5 hours for the regular product and 8 hours for the controlled release product. The elimination half-life is 20 hours. Half-life is prolonged in the elderly and with cirrhosis.
Reference Values
20-65 ng/mL
Cautions
Specimens that are obtained from gel tubes are not acceptable as the drug can absorb on the gel and lead to falsely decreased concentrations.
Day(s) Performed
Thursday
Report Available
1 to 4 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
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
80299