Monitoring sulfamethoxazole therapy to ensure drug absorption, clearance, or compliance
Bactrim (order both tests)
Bactrim (Sulfamethoxazole and trimethoprim)
Gantanol (Sulfamethoxazole)
SEPTRA (Sulfamethoxazole and Trimethoprim)
Sulfamethoxazole
Sulfamethoxazole and Trimethoprim (Bactrim, SEPTRA)
Trimethoprim and Sulfamethoxazole (Bactrim, SEPTRA)
Serum Red
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. Centrifuge and aliquot serum into a plastic vail within 2 hours of collection.
If not ordering electronically, complete, print, and send a Therapeutics Test Request (T831) with the specimen.
0.2 mL
Gross hemolysis | OK |
Gross lipemia | OK |
Gross icterus | OK |
Specimen Type | Temperature | Time | Special Container |
---|---|---|---|
Serum Red | Refrigerated (preferred) | 28 days | |
Ambient | 28 days | ||
Frozen | 28 days |
Monitoring sulfamethoxazole therapy to ensure drug absorption, clearance, or compliance
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 2 to 3 hours after an oral dose. Its average elimination half-life is 6 to 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.
>50 mcg/mL (Peak)
Peak concentrations of sulfamethoxazole should be obtained 1 hour after the end of an IV 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.
Specimens collected in serum gel tubes are not acceptable, as the drug can absorb on the gel and lead to falsely decreased concentrations.
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 Feb;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 Nov 11;76:104-9. 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 Apr;98(4):258-259
4. Avdic E, Cosgrove SE: Management and control strategies for community-associated methicillin-resistant Staphylococcus aureus. Expert Opin Pharmacother. 2008 Jun;9(9):1463-79. doi: 10.1517/14656566.9.9.14635. 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):107-13. 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 edition.. McGraw-Hill Publishing; 2018
Samples are extracted with analyte detection by tandem mass spectrometry.(Unpublished Mayo method)
Monday, Thursday
This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.
80299
Test Id | Test Order Name | Order LOINC Value |
---|---|---|
SFZ | Sulfamethoxazole, S | 10342-4 |
Result Id | Test Result Name |
Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
---|---|---|
8238 | Sulfamethoxazole, S | 10342-4 |