The sulfonamides were the first non-antibiotic, antibacterial agents, used prior to the discovery of Penicillins. They are synthetic agents, which are primarily bacteriostatic.
Sulfonamides act as an anti-metabolite and compete for the enzyme involved in making folic acid. In doing this it renders the folic acid nonfunctional and prevents the growth of microorganisms.
Those organisms susceptible to the sulfonamides are Pneumococci, Group A Streptococci, E. coli, Pasturella pestis, Bacillus anthracis, Shigella, and Haemophylis.
The presence of pus or necrotic tissue will interfere with efficacy of the sulfonamides. For this reason their use is not recommended for application to skin in wounds, or for ophthalmic or vaginal infections.
Drugs of this category are absorbed from the GI tract and are widely distributed to body fluids, cerebral spinal fluid, tissue, central nervous system, and cross placental and fetal barrier.
The sulfonamides are filtered through the glomerulus and excreted in urine, though some are reabsorbed in the kidney. If urine is highly acidic the sulfonamides may precipitate causing crystalluria, hematuria, and renal shutdown. Encouraging fluids to keep urine dilute helps to prevent this.
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