5 Questions
What is the main route of excretion for oral absorbable sulfonamides?
Glomerular filtration
What is the main clinical use of Sulfadoxine+pyrimethamine (Fansidar)?
Malaria
What is the main metabolic pathway for oral absorbable sulfonamides?
Acetylation or glucuronidation
Which organ is included in the widely distributed areas for oral absorbable sulfonamides?
CNS
How are oral nonabsorbable sulfonamides like Sulfasalazine used?
In inflammatory bowel disease
Study Notes
Sulfonamides
- Inhibit bacterial folate synthesis, which is essential for DNA production.
- Sulfonamide-susceptible organisms, unlike mammals, cannot use exogenous folate and must synthesize it from PABA.
Spectrum of Activity
- Inhibit Gram-positive bacteria, such as Staphylococcus.
- Inhibit Gram-negative bacteria, including Escherichia coli, Klebsiella pneumoniae, Salmonella, Shigella, and Enterobacter.
- Inhibit Nocardia, Chlamydia trachomatis, and some protozoa.
- Have poor activity against anaerobes.
- Pseudomonas aeruginosa is intrinsically resistant to sulfonamide antibiotics.
Mechanism of Action
- Act as PABA analogues.
- Inhibit dihydropteroate synthase, which is necessary for folate production within bacteria.
- Mammalian cells, which depend on exogenous sources of folate, are not affected.
Resistance to Sulfonamides
- May occur due to mutations that:
- Cause overproduction of PABA.
- Cause production of a folic acid synthesizing enzyme with low affinity for sulfonamides.
- Impair permeability to the sulfonamide.
Classification of Sulfonamides
- Classified into three categories:
- Oral absorbable.
- Oral non-absorbable.
- Topical.
Test your knowledge of sulfonamides and related compounds with this quiz. Explore the mechanism of action, spectrum of activity, and properties of these bacteriostatic agents that inhibit bacterial folate synthesis.
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