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Test Code SFZ Sulfamethoxazole, Serum

Reporting Name

Sulfamethoxazole, S

Useful For

Monitoring sulfamethoxazole therapy to ensure drug absorption, clearance, or compliance

Method Name

Liquid Chromatography Mass Spectrometry (LC-MS/MS)

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 (gel tubes/SST are not acceptable)

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions:

1. Serum for a peak level should be collected 60 minutes after dose.

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


Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Red Refrigerated (preferred) 28 days
  Ambient  28 days
  Frozen  28 days

Reject Due To

Gross hemolysis OK
Gross lipemia OK
Gross icterus OK

Reference Values

>50 mcg/mL (Peak)

Day(s) Performed

Monday, Thursday

CPT Code Information

80299

LOINC Code Information

Test ID Test Order Name Order LOINC Value
SFZ Sulfamethoxazole, S 10342-4

 

Result ID Test Result Name Result LOINC Value
8238 Sulfamethoxazole, S 10342-4

Clinical Information

Sulfamethoxazole is a sulfonamide antibiotic that is administered in conjunction with another antibacterial, trimethoprim. These agents are used to treat a variety of infections, including methicillin-resistant Staphylococcus aureus, and for prophylaxis in immunosuppressed patients, such as individuals who are HIV positive.

 

Therapeutic drug monitoring is not commonly performed unless there are concerns about adequate absorption, clearance, or compliance. Monitoring of sulfamethoxazole is indicated only when prolonged (>3 months) therapy is required.

 

Sulfamethoxazole is absorbed readily after oral administration, with peak serum concentration occurring 1 to 4 hours after an oral dose. Its average elimination half-life is approximately 10 hours. Toxicity includes crystalluria with resultant calculi and kidney disease. Toxicity is due to a high concentration of acetylated, relatively insoluble forms of the drug. Excess fluid should be taken with sulfamethoxazole to avoid formation of urine sulfonamide crystals.

Specimen Retention Time

14 days

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.

Report Available

2 to 5 days

Forms

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