Sulfonamides :Chemotherapy of microbial diseases, Assignments of Pharmacology

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SULFONAMIDES

BY: SHILPI MISHRA

Sulfonamides were the first antimicrobial agents (AMAs) effective against

pyogenic bacterial infections.

Classification:

1. Short acting (4–8 hr): Sulfadiazine 2. Intermediate acting (8–12 hr): Sulfamethoxazole 3. Long acting (~7 days): Sulfadoxine, Sulfamethopyrazine 4. Special purpose sulfonamides: Sulfacetamide sod., Mafenide, Silver

sulfadiazine, Sulfasalazine

Mechanism of action

Drugs

 Sulfadiazine: It is rapidly absorbed orally and rapidly excreted in urine. It is 50%

plasma protein bound and 20–40% acetylated. It has good penetrability in brain and

CSF—was the preferred compound for meningitis.

 Sulfamethoxazole: It has slower oral absorption and urinary excretion—

intermediate duration of action, t½ in adults averages 10 hours. It is the preferred

compound for combining with trimethoprim because the t½ of both is similar.

 Sulfadoxine, Sulfamethopyrazine: These are ultralong acting compounds, action

lasting > 1 week because of high plasma protein binding and slow renal excretion (t½

5–9 days).

 Sulfacetamide sod.: It is a highly soluble compound yielding neutral solution

which is only mildly irritating to the eye in concentrations up to 30%. It is used

topically for ocular infections due to susceptible bacteria.

USES

 Systemic use of sulfonamides alone. Though they can be employed for suppressive

therapy of chronic urinary tract infection, for streptococcal pharyngitis and gum

infection; such uses are outmoded.

 Trimethoprim + Sulfonamide (as Cotrimoxazole ) sulfamethoxazole is used for many

bacterial infections.

 Along with pyrimethamine, certain sulfonamides are used for malaria.

 Ocular sulfacetamide sod. (10–30%) is a cheap alternative in trachoma/inclusion

conjunctivitis, though additional systemic azithromycin or tetracycline therapy is

required for eradication of the disease.

 Topical silver sulfadiazine or mafenide are used for preventing infection on burn

surfaces.