Trimethoprim-13C3is the deuterium labeledTrimethoprim(HY-B0510)[1]. Trimethoprim is a bacteriostatic antibiotic and an orally active dihydrofolate reductase inhibitor. Trimethoprim is active against a wide range of Gram-positive and Gram-negative aerobic bacteria. Trimethoprim has the potential for the research of urinary tract infections, Shigellosis and Pneumocystis pneumonia. Trimethoprim can inhibit infection of Influenza A virus in chick embryo when combinated with zinc[2][3][4][5].