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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

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

Reference Values

>50 mcg/mL (Peak)

Day(s) Performed

Monday, 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

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

Interpretation

Peak concentrations of sulfamethoxazole should be obtained 1 hour after the end of an intravenous dose or 2 to 3 hours after an oral dose, while peak concentrations of trimethoprim can be collected at least 1 hour after an oral dose. Serum drug concentrations should be interpreted with respect to the minimal inhibitory concentration of targeted organisms. Most patients will display peak steady-state serum concentrations greater than 50 mcg/mL when collected at least 1 hour after an oral dose. Target concentrations may be higher, depending on the intent of therapy.

 

For Pneumocystis carinii pneumonia (PCP pneumonia), peak concentrations: 100-150 mcg/mL

Toxicity: >200 mcg/mL

Toxicity (formation of urinary crystals) associated with sulfamethoxazole occurs with prolonged exposure to serum concentrations greater than 125 mcg/mL.

 

Trimethoprim: Most patients will display peak steady-state serum concentrations of more than 2.0 mcg/mL when the specimen is collected at least 1 hour after an oral dose. Target concentrations may be higher depending on the intent of therapy.

Clinical Reference

1. Hughes WT, Feldman S, Chaudhary SC, Ossi MJ, Cox F, Sanyal SK. Comparison of pentamidine isethionate and trimethoprim-sulfamethoxazole in the treatment of Pneumocystis carinii pneumonia. J Pediatr. 1978;92(2):285-291. doi:10.1016/s0022-3476(78)80028-6

2. Dao BD, Barreto JN, Wolf RC, Dierkhising RA, Plevak MF, Tosh PK. Serum peak sulfamethoxazole concentrations demonstrate difficulty in achieving a target range: a retrospective cohort study. Curr Ther Res Clin Exp. 2014;76:104-109. doi:10.1016/j.curtheres.2014.08.003

3. Young T, Oliphant C, Araoyinbo I, Volmink J. Co-trimoxazole prophylaxis in HIV: the evidence. S Afr Med J. 2008;98(4):258-259

4. Avdic E, Cosgrove SE. Management and control strategies for community-associated methicillin-resistant Staphylococcus aureus. Expert Opin Pharmacother. 2008;9(9):1463-1479. doi:10.1517/14656566.9.9.1463

5. Kamme C, Melander A, Nilsson N. Serum and saliva concentrations of sulfamethoxazole and trimethoprim in adults in children: relation between saliva concentrations and in vitro activity against nasopharyngeal pathogens. Scand J Infect Dis. 1983;15(1):107-113. doi:10.3109/inf.1983.15.issue-1.18

6. Brunton LL, Hilal-Dandan R, Knollmann BC, eds. Goodman, Gilman's: The Pharmacological Basis of Therapeutics. 13th ed. McGraw-Hill Publishing; 2018

Report Available

2 to 5 days

Method Name

Liquid Chromatography Mass Spectrometry (LC-MS/MS)

Forms

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