• Trimethoprim lactate packaged and labeled.

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SKU: T012

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Trimethoprim is a bactericidal dihydrofolate reductase inhibitor. Trimethoprim prevents bacteria from taking up folic acid which is used to synthesize the essential DNA nucleotide thymine.

TOKU-E offers two forms of trimethoprim: trimethoprim (T011) and trimethoprim lactate (T012). Trimethoprim is slightly soluble in aqueous solution (12.1 mg/mL). Trimethoprim lactate is freely soluble in aqueous solution (19.6 mg/mL).

    CAS Number


    Molecular Formula

    C14H18N4O3 · C3H6O3

    Molecular Weight

    380.40 g/mol

    Mechanism of Action

    Trimethoprim acts by interfering with the action of bacterial dihydrofolate reductase, inhibiting synthesis of tetrahydrofolic acid. Tetrahydrofolic acid is an essential precursor in the de novo synthesis of the intermediate Thymidine monophosphate (dTMP), precursor of DNA metabolite Thymidine triphosphate.

    Storage Conditions

    2-8 ┬░C

    Tariff Code



    Trimethoprim is a broad spectrum antibiotic used extensively against bacteria responsible for urinary tract infections.


    Microbiology Applications

    Trimethoprim is commonly used in clinical in vitro microbiological antimicrobial susceptibility tests (panels, discs, and MIC strips) against gram positive and gram negative microbial isolates. Medical microbiologists use AST results to recommend antibiotic treatment options for infected patients. Representative MIC values include:

    • Escherichia coli 0.25 µg/mL - 64 µg/mL
    • Haemophilus influenzae 0.15 µg/mL - 16 µg/mL
    • For a complete list of trimethoprim MIC values, click here.

    Plant Biology Applications

    Trimethoprim can be used in combination with rifampicin to provide sufficient coverage against pathogenic microbes. When used without other supplemental antibiotics, trimethoprim was not shown to provide sufficient coverage (Pollock et al.1983).





    White or off-white powder



    Weir, D. G., and J. Scott. "Mechanism of the Antimicrobial Drug Trimethoprim Revisited."PubMed (2000): 2519-524. www.ncbi.gov. 14 Dec. 2000. Web. 21 Aug. 2012.

    Kneifel W. and Leonhardt W., Testing of different antibiotics against Gram-positive and Gram-negative bacteria isolated from plant tissue culture. Plant Cell, Tissue and Organ Culture, Vol. 29, pp. 139-144, 1992.

    Pollock K., Barfield D.G. and Shields R., The toxicity of antibiotics to plant cell cultures. Plant cell reports, Vol. 2, pp. 36-39, 1983.

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