Medications and Drugs
GENERIC NAME: sulfamethoxazole
BRAND NAME: Gantanol
DRUG CLASS AND MECHANISM: Sulfamethoxazole is an anti-
bacterial
sulfonamide. It prevents the formation of dihydrofolic acid, a
compound
that bacteria must be able to make in order to survive.
Although it was
once a very useful antibiotic, it is almost obsolete as a
single agent
today due to the development of bacterial resistance to its
effects.
Sulfamethoxazole is now used primarily in combination with
trimethoprim, a
combination product known as Bactrim or Septra.
Sulfamethoxazole was
approved by the FDA in 1961.
PRESCRIPTION: yes
GENERIC AVAILABLE: yes
PREPARATIONS: Tablets (light green; round): 500 mg.
STORAGE: The tablets should be kept at room
temperature, 15-30°C
(59-86°F).
PRESCRIBED FOR: Sulfamethoxazole is used for the
treatment of
malaria (in combination with quinine sulfate and pyrimethamine),
conjunctivitis (inflammation of the conjunctiva of the eye) due
to
chlamydia, toxoplasmosis (in combination with pyrimethamine),
and urinary
tract infections (UTI).
DOSING: Sulfamethoxazole usually is taken two or three
times
daily, with or without meals. It should be taken with 6 to 8
ounces of
liquid to prevent crystals from forming in the urine. Persons
with
advanced kidney diseases may require lower doses.
DRUG INTERACTIONS: Sulfamethoxazole can enhance the
blood-thinning effects of warfarin (Coumadin), possibly leading
to
bleeding. Sulfonamides such as sulfamethoxazole can increase the
metabolism (break-down and elimination) of cyclosporine
(causing loss of
effectiveness of cyclosporine), and can add to the kidney
damage caused by
cyclosporine. All sulfonamides can crystallize in urine when
the urine is
acidic. Since methenamine causes an acidic urine, it should not
be used
with sulfonamides.
PREGNANCY: The effects of the sulfonamide class of
antibiotics
on the fetus have not been adequately studied. Physicians may
elect to use
them if the benefits are deemed to outweigh potential risks. On
the other
hand, use of sulfonamides near term (that is, near the ninth
month of
pregnancy) may cause bilirubin to be displaced from proteins in
the
infant's blood. Displacement of bilirubin can lead to a
dangerous
condition called kernicterus in which the bilirubin damages the
brain. For
this reason, sulfonamides should not be used near term.
NURSING MOTHERS:
Sulfamethoxazole is excreted in breast
milk and
should not be used in women who are breast-feeding.
Sulfonamides can cause
kernicterus in nursing newborns.
SIDE EFFECTS: Sulfamethoxazole may cause dizziness,
headache,
lethargy, diarrhea, anorexia, nausea,
vomiting, and rash.
Sulfamethoxazole
should be stopped at the first appearance of a skin rash since
the rash
may become severe. Serious rashes include Stevens-Johnson
syndrome (aching
joints and muscles; redness, blistering, and peeling of the
skin); toxic
epidermal necrolysis (difficulty in swallowing; peeling,
redness,
loosening, and blistering of the skin). Sulfamethoxazole
therapy also can
cause extensive sunburn, following exposure to sunlight.
Patients
receiving sulfamethoxazole should avoid excessive exposure to
sunlight and
should wear sunscreen.
Other rare side effects include liver damage, low white blood
cell
count, low platelet count, and anemia.
Sulfamethoxazole may form crystals in the urine which may
damage the
kidney and cause bleeding into the urine. It is important to
drink
additional liquids during sulfonamide therapy to prevent these
side
effects.
Reference: FDA Prescribing Information
Last Editorial Review: 12/31/1997
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
- Drug Interactions - Learn about potential drug interactions you may be exposed to. Drug interactions can occur with prescription drugs, OTC medication, vitamins, herbs, and supplements.
- Liver Blood Tests - Learn about liver blood tests used to detect liver damage disease such as fatty liver, cirrhosis, hepatitis, Tylenol liver damage, and more. This includes measuring the aminotransferases enzymes (AST and ALT levels)
- Urinary Tract Infection (UTI In Adults) - Learn about urinary tract infection causes, symptoms, signs, diagnosis and treatment of UTIs in men and women. Antibiotics may be used to treat recurrent bladder infections.
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