Trimethoprim
Also known as: Proloprim, Trimpex, Monotrim (as TMP alone); Bactrim, Septra, Cotrim (as co-trimoxazole with SMX)
CAS Number: 738-70-5
Diaminopyrimidine — dihydrofolate reductase inhibitor
Pharmacopeia Standards
Mechanism of Action
Diaminopyrimidine that selectively inhibits bacterial dihydrofolate reductase (DHFR) with ~50,000-fold greater affinity for bacterial vs. human enzyme. Blocks conversion of dihydrofolate to tetrahydrofolate, depleting the one-carbon carriers required for thymidylate, purine, and amino acid synthesis. Bacteriostatic alone; bactericidal in combination with sulfamethoxazole (TMP-SMX = co-trimoxazole). Sequential blockade of folate synthesis pathway.
Technical Specifications
| Generic / INN Name | Trimethoprim |
| CAS Registry Number | 738-70-5 |
| Molecular Formula | C14H18N4O3 |
| Molecular Weight | 290.32 g/mol |
| Typical Purity | 99.0–101.0% |
| Storage Conditions | Store below 25°C, protected from light |
| Shelf Life | 36 months from date of manufacture |
| Category | Sulfonamides |
Specifications are indicative and intended for sourcing reference only. Always confirm against the supplier's Certificate of Analysis and the applicable pharmacopeial monograph before issuing a purchase specification.
Typical Applications
Urinary tract infections (as TMP alone or TMP-SMX — first-line for uncomplicated cystitis in many guidelines), Pneumocystis jirovecii pneumonia (PCP) prophylaxis and treatment (TMP-SMX — gold standard in HIV), MRSA SSTI (TMP-SMX — widely used in community settings), Stenotrophomonas maltophilia (TMP-SMX — one of few active agents), Nocardia infections, toxoplasmosis (pyrimethamine is preferred but TMP-SMX used in CNS prophylaxis), traveler's diarrhea, Cyclospora.
Manufacturers (2+)
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