Folate Synthesis Inhibitors Part 4

What is the spectrum of activity of sulfonamides?

Broad-spectrum.

Sulfonamides are effective against which Gram-positive organisms?

Many susceptible Gram-positive bacteria.

Sulfonamides are effective against which Gram-negative organisms?

Many susceptible Gram-negative bacteria.

Which filamentous bacteria are susceptible to sulfonamides?

Nocardia and Actinomyces spp.

Which protozoa are susceptible to sulfonamides?

Coccidia and Toxoplasma spp.

Name common diseases treated with sulfonamides.

Actinobacillosis, coccidiosis, mastitis, metritis, colibacillosis, pododermatitis, polyarthritis, respiratory infections, and toxoplasmosis.

Why is the human classification of short-, medium-, and long-acting sulfonamides not suitable in veterinary medicine?

Because drug disposition and elimination differ among animal species.

What are the standard-use sulfonamides?

Sulfamethazine, sulfamerazine, sulfadiazine, sulfabromomethazine, sulfaethoxypyridazine, and sulfadimethoxine.

What is the primary indication for standard-use sulfonamides?

Systemic infections.

Which sulfonamides are classified as highly soluble?

Sulfisoxazole (sulfafurazole), sulfasomidine, and sulfamethoxazole.

What is the primary indication for highly soluble sulfonamides?

Urinary tract infections.

Which sulfonamides are used topically?

Sulfacetamide, mafenide, silver sulfadiazine, and sulfathiazole.

What is sulfacetamide primarily used to treat?

Ophthalmic infections.

What is silver sulfadiazine primarily used to treat?

Burn wounds.

Why is sulfacetamide suitable for ophthalmic preparations?

It can be prepared as a sodium salt at neutral pH.

Which sulfonamide is primarily used for inflammatory bowel disease rather than antibacterial activity?

Sulfasalazine.

What conditions is sulfasalazine used to treat?

Colitis and inflammatory bowel disease in dogs and cats.

What are potentiated sulfonamides?

Combinations of a sulfonamide and a diaminopyrimidine with synergistic bactericidal activity.

Name the major diaminopyrimidines.

Trimethoprim, ormetoprim, aditoprim, tetroxoprim, methoprim, and pyrimethamine.

Give examples of potentiated sulfonamide combinations.

Trimethoprim-sulfadiazine, trimethoprim-sulfamethoxazole, trimethoprim-sulfadoxine, and ormetoprim-sulfadimethoxine.

Compared with sulfonamides alone, potentiated sulfonamides have increased activity against which bacteria?

Streptococcus, Staphylococcus, Salmonella, Pasteurella, Corynebacterium, and Escherichia coli.

Which organisms may initially be susceptible but commonly develop resistance to potentiated sulfonamides?

Enterobacter, Klebsiella, Proteus, Clostridium, and Leptospira spp.

Which organisms are highly resistant to potentiated sulfonamides?

Rickettsiae, protozoa, coccidia, mycoplasmas, Pseudomonas, Bacteroides, and most Chlamydia.

What is the optimal in vitro ratio of trimethoprim to sulfonamide?

Approximately 1:20.

What trimethoprim-to-sulfonamide ratio is used in commercial preparations?

1:5.

Why is a 1:5 ratio used in commercial preparations instead of 1:20?

Pharmacokinetic differences produce an effective ratio at the site of infection.

What type of infection is especially suitable for trimethoprim-sulfonamide combinations?

Prostatic infections.