Trimethoprim-d3is the deuterium labeled Trimethoprim. 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 urinary tract infections, Shigellosis and Pneumocystis pneumonia treatment[1][2][3].