Trimethoprim - Dihydrofolate Reductase Inhibitors

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WIKIDRUGS
ANTIBIOTICS


Trimethoprim


Mechanism of Action

Sulphonamides act by competing with an essential precursor in folic acid synthesis in bacteria. Bacteria need to synthesise folic acid in order to grow as they are unable to obtain it from their 'diet' like mammals can. Since the bacteria is unable to synthesise RNA or DNA, due to it's lack of folic acid, it's growth is inhibited. As such sulphonamides are bacteriostatic.


Spectrum of Activity

Pharmacokinetic Considerations

Dihydrofolate reductase inhibitors: Lipophilic weak bases. • Orally active. • Widely distributed throughout the body, ion trapped in acidic fluids. • Cleared by hepatic metabolism – rate varies with species and individual drug (trimethoprim rapidly metabolised by most veterinary species).

Side Effects and Contraindications