Yale New Haven Hospital

Department of Laboratory Medicine
Test Directory

[ Test Name Index ]

[ Home & References ]


Lab Section: 

Sendout Reference


Lab Location: 


Reference Lab: 



Test ID: 




Bactrim, Blood; Gantanol; SEPTRA


High-Performance Liquid Chromatography (HPLC)


Monday, Thursday


7 days

Specimen Requirements: 

Collection: 3.0 mL Blood in a Red Top Tube.
Pediatric volume: 1 mL.
Plain, red-top tube; Serum for a peak level should be drawn 60 minutes after dose; Spin specimen down within 2 hours of draw; Send specimen in plastic vial
Transport: Refrigerated.
Unacceptable conditions: Serum gel tube
Stability: Refrigerated (preferred): 28 days; Ambient: 28 days; Frozen: 28 days



Clinical Indications: Monitoring 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 HIV-positive individuals. 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 renal 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.

Reference Interval: 

See patient report or consult reference laboratory website.


CPT Code(s): 


Last Changed: 

8/23/2017 5:29:02 PM

Last Reviewed: 

8/23/2017 5:29:10 PM