Test Overview
Clinical Utility
Monitoring trimethoprim therapy to ensure drug absorption, clearance, or compliance.
Trimethoprim is coadministered with sulfamethoxazole for prophylaxis or treatment of bacterial infections. 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.
Trimethoprim has a wide therapeutic index and dose-dependent toxicity. Trimethoprim accumulates in patients with renal failure.
Therapeutic drug monitoring is not commonly performed unless there are concerns about adequate absorption, clearance, or compliance. Accordingly, routine drug monitoring is not indicated in all patients.
Method
High Performance Liquid Chromatography (HPLC)
Method Description
Acetonitrile precipitation with analysis by HPLC. (Unpublished Mayo method)
Result Included
Trimethoprim
Aliases/Synonyms
Bactrim (Sulfamethoxazole and Trimethoprim); Septra (Sulfamethoxazole and Trimethoprim)
Specimen
Specimen Type
SerumContainers
Collection Containers
Red top (no additive)
Volume
Sample Volume
1.0 mL
Minimum Volume
0.2 mL
Collection & Handling
Collection Instructions
Serum for a peak level should be drawn at least 60 minutes after a dose.
Handling Information
Separate within 2 hours.
Stability
| Ambient | Refrigerated | Frozen |
|---|---|---|
| 28 days | 28 days | 28 days |
Performance & Interpretation
Turnaround Time
10 days
Results
-
Trimethoprimmcg/mL>2.0
Comment
Most patients will display peak steady state serum concentrations >2.0 mcg/mL when drawn at least 1 hour after an oral dose. Target concentrations may be higher, depending on the intent of therapy.
Referral Location
Out-of-Country
Interface & Setup
HL7 Interface Codes
| Order Code | Result Name | Result Codes | Units |
|---|---|---|---|
| TRIME S | Trimethoprim, S | 63338 | mcg/mL |
Test Version
Last Updated
2020-02-27