Sulfonamides (classification, adverse effects and uses)

                   SULFONAMIDES

First antimicrobial agents effective against pyogenic bacterial infections were sulfonamides. 

Chemistry

They are considered as derivative of sulfanilamide(p-aminobenzene sulfonamides). 

Examples of sulfonamides include:

• sulfamethoxazole/trimethoprim (Bactrim, Bactrim DS, Septra, Septra DS)

• sulfasalazine (Azulfidine, Sulfazine)

• sulfisoxazole (Truxazole)

What formulations are sulfonamides are available?

tablets, injections, and oral solutions.

Classication

1.Short Acting (4-8hr) -

Sulfadizine

2.Intermediate acting (8-12hr) -

Sulfamethoxazole

3.Long Acting(~7days) 

Sulfadoxine

4.Special purpose sulfonamides-

Sulfacetamide sod., Mafenide, silver sulfadiazine, sulfasalazine. 

Adverse effects of Sulfonamides

a)   Nausea, vomiting and epigastric pain are common. 

b) Neutropenia are rare. 

c)Hypersensitivity reaction like rashes,  urticaria and drug fever are common and occurs in 2-5%of patients. 

d)Hepatitis unrelated to dose occurs in 0.1% of patients. 

e) Topical use of sulfonamides is not recommended because of risk of contact sensitization. 

f) crystalluria is dose related but infrequent now. 

g) cause haemolysis in patients with G-6-PD deficiency. 

Uses of sulfonamides

a) Topical silver sulfadiazine or Mafenide are used for preventing infections on burn surfaces. 

b) Ocular sulfacetamide sod. (10-30%)  as an alternative in trachoma/ inclusion conjunctivitis. 

c) Systemic use of sulfonamides alone is rare now. They can be employed for suppressive therapy of chronic urinary tract infections, streptococcal pharyngitis and gum infections.

What about taking sulfonamides during pregnancy or while breastfeeding?

Use of sulfonamides may cause bilirubin to be displaced from proteins in the infant's blood. Displacement of bilirubin can lead to jaundice and a dangerous condition called kernicetrus in the infant. si this  is the reason sulfamethoxazole/ trimethoprim should not be used near term (late in pregnancy) among women. Sulfonamides should not be used by nursing  mothers because sulfamethoxazole is excreted in breast milk and can cause kernicterus.