Триметоприм

Trimethoprim selectivity between bacterial and mammalian dihydrofolate reductases results from the subtle but significant architectural differences between these enzyme systems. Whereas the bacterial enzyme and the mammalian enzyme both efficiently catalyze the conversion of dihydrofolic acid to tetrahydrofolic acid, the bacterial enzyme is sensitive to inhibition by trimethoprim by up to 40,000-fold lower concentrations than the mouse enzyme is. This difference explains the useful selective toxicity of trimethoprim.

Crystalline

An antibacterial and inhibitor of formylation. Dihydrofolate reductase inhibitor with selectivity for the prokaryote enzyme.Trimethoprim is an antibiotic involved in the treatment of urinary tract infections, middle ear infections and traveler?s diarrhea. It is associated with sulfamethoxazole and interferes with the cellular metabolism of folic acid in the bacterial cell by blocking the biosynthesis of nucleotides. Furthermore, It is also used to treat and prevent Pneumocystis jiroveci pneumonia.

Trimethoprim has a broad spectrum of antimicrobial activity. It is 20–100 times more active than sulfamethoxazole with respect to most bacterial forms. Trimethoprim is active with respect to Gram-positive, aerobic bacteria such as Staphylococcus aureus, Staphylococcus epidermidis, and various types of Streptococcus and Listeria monocytogenes. Trimethoprim is inferior to sulfonamides against forms of Nocardia. It is active with respect to Gram-negative, aerobic bacteria such as most E. coli, Enterobacter, Proteus, Klebsiella, Providencia, Morganella, Serratia marcescens, Citrobacter, Salmonella, Shigella, Yersinia enterocolitica that are sensitive to trimethoprim. Trimethoprim is also active with respect to Legionella, Acinetobacter, Vibrio, Aeromonas, Pseudomonas maltophila, P. cepacia, although P. aeruginosa is resistant to trimethoprim.

Odorless white powder. Bitter taste.

Insoluble in water.

Trimethoprim readily forms salts with acids. .

Flash point data for Trimethoprim are not available. Trimethoprim is probably combustible.

Haemophilus influenzae and H. ducreyi are sensitive to trimethoprim. Pathogenic Neisseria (meningococci and gonococci) and Branhamella catarrhalis are moderately resistant to trimethoprim, although they are very sensitive to a combination of trimethoprim and sulfamethoxazole. Anaerobic bacteria in general are resistant to trimethoprim, although a combination of trimethoprim-sulfamethoxazole does have an effect on them. Pneumocystis carinii is also sensitive to that combination.
Bacterial resistance to trimethoprim can originate because of a number of reasons: inability of the drug to penetrate through the membrane (P. aeruginosa); the presence of dihydrofolate reductase that is not sensitive to inhibition by trimethoprim; overproduction of dihydrofolate reductase and mutation expressed as thyminic dependence, when the organism requires exogenic thymine for synthesizing DNA, i.e. bypassing metabolic blockage caused by trimethoprim.
Resistance to a combination of trimethoprim-sulfamethoxazole is always less frequent than when any of these drugs is used separately. This combination of drugs, which is known by the commercial names cotrimoxazole, bactrim, biseptol, sulfatrim, and many others, is used for treating infections of the respiratory tract, infections of the urinary tract, gastric infections, surgical infections, enteritis, meningitis, and other diseases.

Trimethoprim (5-[(3,4,5-trimethoxyphenyl)methyl]-2,4-pyrimidinediamine or 2,4-diamino-5-(3,4,5-trimethoxybenzyl)pyrimidine) is closely related to several antimalarialsbut does not have good antimalarial activity by itself; it is,however, a potent antibacterial. Originally introduced incombination with sulfamethoxazole, it is now available as asingle agent.
Approved by the FDA in 1980, trimethoprim as a singleagent is used only for the treatment of uncomplicatedurinary tract infections. The argument for trimethoprim asa single agent was summarized in 1979 by Wormser andDeutsch. They point out that several studies comparingtrimethoprim with TMP–SMX for the treatment ofchronic urinary tract infections found no statistically relevantdifference between the two courses of therapy.The concern is that when used as a single agent, bacterianow susceptible to trimethoprim will rapidly developresistance. In combination with a sulfonamide, however,the bacteria will be less likely to do so. That is, they willnot survive long enough to easily develop resistance toboth drugs.