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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.
Monitoring trimethoprim therapy to ensure drug absorption, clearance, or compliance
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.
No significant cautionary statements
1. 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;15:107-113
2. Young T, Oliphant C, Araoyinbo I, Volmink J: Co-trimoxazole prophylaxis in HIV: the evidence. S Afr Med J 2008 April;98(4):258-259
3. Avdic E, Cosgrove S: Management and control strategies for community-associated methicillin-resistant Staphylococcus aureus. Expert Opin Pharmacother 2008 June;9(9):1463-1479
4. Goodman and Gilman's: The Pharmacological Basis of Therapeutics. 11th edition. McGraw-Hill Publishing, 2006, p 1112