a. The sulfonamides are bacteriostats. They stop bacterial growth by interfering
with the production of folic acid in the bacteria cells. They do not interfere with human
utilization of folic acid.
b. The ranges of effectiveness of the various sulfonamides are very similar to
each other. However, some sulfonamides may be more potent against specific types of
infection than others. The sulfonamides are effective against gram-positive and gram-
negative bacteria, as well as several other types of microorganisms.
a. Indications. Sulfisoxazole (Gantrisin) is rapidly absorbed and rapidly
excreted. It is useful in:
(1) Acute, recurrent, or chronic urinary tract infections (primarily cystitis,
pyelitis, pyelonephritis) because of susceptible organisms (usually E. coli, Klebsiella-
Aerobacter, Staphylococcus, Staphylococcus aureus, Proteus mirabilis).
Meningococcal meningitis because of susceptible organisms.
(3) Haemophilus influenzae meningitis when used with parenteral
streptomycin; acute otitis media because of H. influenzae when used with adequate
b. Usual Dosage.
Child. The initial dose for children is one-half of the 24-hour dose. The
maintenance dose is 150 mg/kg/24 hours or 4 grams/m is 6 grams.
Systemic sulfonamides are contraindicated for infants under two months of
(2) Adult. The initial adult dose is 2 to 4 grams. The maintenance dose is 4
to 8 grams daily, divided into 4 to 6 doses.