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Drug Profile

The information on this site is intended to supplement and enhance, not replace, the advice of a physician who is familiar with your medical history. Decisions about your health should always be made ONLY after detailed conversation with your doctor.

Generic drug name: sulfisoxazole (sul fi SOX a zole)
Brand name(s):
GENERIC: available FAMILY: Sulfonamides
Find the drug label by searching at DailyMed.

Generic drug name: trimethoprim and sulfamethoxazole (trye METH oh prim and sul fa meth OX a zole)
Brand name(s): BACTRIM, BACTRIM DS, PRIMSOL, SEPTRA, SEPTRA DS, SULFATRIM PEDIATRIC
GENERIC: available FAMILIES: Sulfonamides, Sulfonamides with Synthetic Antibacterial
Find the drug label by searching at DailyMed.

Pregnancy and Breast-feeding Warnings [top]

Pregnancy Warning

Sulfisoxazole caused harm to developing fetuses in animal studies, including cleft palates, malformations, brain damage, and death. Because of the potential for serious adverse effects to the fetus, these drugs should not be used by pregnant women.

Breast-feeding Warning

Sulfonamides are excreted in human milk. Because of the potential for serious adverse effects in nursing infants, you should not take these drugs while nursing.

Facts About This Drug [top]

Both sulfisoxazole and trimethoprim with sulfamethoxazole (BACTRIM, BACTRIM DS, SEPTRA, SEPTRA DS, SULFATRIM PEDIATRIC) are drugs from a class called sulfonamides, or sulfa drugs.

Sulfisoxazole is used to treat urinary tract infections and some other infections. Patients with kidney or liver damage should take less than the usual adult dose. Sulfisoxazole will not help a cold or the flu.

Sulfisoxazole is available in several forms. It is often taken by mouth. Another form of the drug, a...

Both sulfisoxazole and trimethoprim with sulfamethoxazole (BACTRIM, BACTRIM DS, SEPTRA, SEPTRA DS, SULFATRIM PEDIATRIC) are drugs from a class called sulfonamides, or sulfa drugs.

Sulfisoxazole is used to treat urinary tract infections and some other infections. Patients with kidney or liver damage should take less than the usual adult dose. Sulfisoxazole will not help a cold or the flu.

Sulfisoxazole is available in several forms. It is often taken by mouth. Another form of the drug, a vaginal cream, is used to treat vaginitis, but there is no evidence that this is an effective treatment. For eye infections, there are eye ointment and eye solution forms of sulfisoxazole that are similar to sulfacetamide.

Trimethoprim with sulfamethoxazole is a combination of the synthetic antibacterial trimethoprim and the sulfa drug sulfamethoxazole. This combination of drugs is commonly used to treat urinary tract infections but is also approved to treat bacterial infections in other parts of the body.

Side effects

A certain type of skin rash called fixed pigmentation erythema has been associated with the use of trimethoprim with sulfamethoxazole. This rash is accompanied by inflammation and leaves the skin pigment permanently darkened.[1]

Deaths have been associated with the use of sulfonamides due to severe skin reactions (including Stevens-Johnson syndrome and toxic epidermal necrolysis), liver toxicity and bone marrow toxicity. Products such as trimethoprim with sulfamethoxazole should be discontinued at the first appearance of skin rash or any sign of an adverse reaction.[2],[3]

In November 2014, Health Canada, an agency similar to the FDA, announced that a safety review of sulfamethoxazole and/or trimethoprim containing products revealed a potential risk of a condition in which there is a low number of blood platelets (platelets prevent bleeding).  This condition also had been reviewed by the FDA, and changes were made to the product labeling in 2012.[4]

Trimethoprim has been linked to birth defects, including spinal cord abnormalities, cleft palate and heart malformations, in children born to women who used trimethoprim during the first trimester.[5] Some  of these defects are likely due to the drug’s ability to interfere with folic acid.

Interactions

In September 2011, the British Medical Journal (BMJ) released the results of important research showing that elderly patients prescribed trimethoprim with sulfamethoxazole in combination with the diuretic spironolactone (ALDACTONE) have a much higher risk of being hospitalized for hyperkalemia (increased levels of potassium in the blood). The risk for hospitalization due to hyperkalemia for elderly patients in the study, all of whom were also taking spironolactone, was much greater for those taking trimethopri with sulfamethoxazole than for those taking either amoxicillin (AMOXIL, AUGMENTIN, LAROTID, MOXATAG) or nitrofurantoin (FURADANTIN, MACROBID, MACRODANTIN). (Read more in the December 2011 Worst Pills, Best Pills News.)

In October 2014, another study in the (BMJ) showed that two classes of medications used to treat high blood pressure, angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs), when used in combination with the antibiotic trimethoprim with sulfamethoxazole, can increase blood potassium levels and can increase the risk of sudden death, most likely due to abnormal heart rhythms.[6] (Read more in the June 2015 Worst Pills, Best Pills News.)

In October 2014, JAMA Internal Medicine published a study showing that older patients taking one of two commonly used oral sulfonylurea diabetes drugs — glipizide (GLUCOTROL, GLUCOTROL XL) or glyburide (DIABETA, GLUCOVANCE, GLYNASE) — in combination with trimethoprim with sulfamethoxazole had an increased risk of developing dangerously low blood sugar levels, a condition known as hypoglycemia.[7] (Read more in the November 2014 Worst Pills, Best Pills News.)

Preventing urinary tract infections

Practice measures to prevent urinary tract infections. Drink plenty of fluids, especially water. (While cranberry juice is unreliable as a cure for urinary tract infections, the juice may reduce odor from incontinence.[8]) Practice meticulous hygiene. For women, after using the toilet, wipe backward, not forward, then wash hands. Prepare and store foods properly, especially when traveling, to prevent diarrhea. Restrict caffeine, which widens the urethra.

Indwelling bladder catheters invite urinary tract infections. However, unless there are symptoms of a urinary infection, it is not always necessary to take medication just because bacteria are found in a urine test.[9]

Women are particularly prone to repeated urinary tract infections. If urinary tract symptoms occur often, ask a doctor about keeping a supply of medication on hand. Ideally, the antibiotic used should be the most effective, least toxic and least costly.[10],[11]

Before You Use This Drug [top]

Do not use if you have or have had allergy to:

Tell your doctor if you have or have had:

  • pregnancy or are breast-feeding
  • allergies to drugs
  • glucose-6-phosphate dehydrogenase deficiency
  • kidney or liver disease
  • porphyria
  • anemia or other blood problems

Tell your doctor about any other drugs you take, including aspirin, herbs, vitamins, and other nonprescription products.

When You Use This Drug [top]

  • If you plan to have any surgery, including dental, tell your doctor that you take this drug.
  • Check with your doctor if there is no improvement within a few days.
  • Have regular visits with your doctor to check your blood.
  • Protect yourself from the sun.
  • If you get dizzy, do not drive or operate heavy machinery.

How to Use This Drug [top]

  • If you miss a dose, take it as soon as you remember, but skip it if it is almost time for the next dose. Do not take double doses.
  • Do not share your medication with others.
  • Take the drug at the same time(s) each day.
  • Maintain adequate fluid intake.
  • Take this drug for the prescribed length of time. If you stop too soon, your symptoms could come back.
  • Take with a full glass (eight ounces) of water and maintain adequate fluid levels.
  • For tablets: Store at room temperature with lid on tightly. Do not store in the bathroom. Do not expose to heat, moisture, or strong light. Keep out of reach of children.

Interactions with Other Drugs [top]

The following drugs, biologics (e.g., vaccines, therapeutic antibodies), or foods are listed in Evaluations of Drug Interactions 2003 as causing “highly clinically significant” or “clinically significant” interactions when used together with any of the drugs in this section. In some sections with multiple drugs, the interaction may have been reported for one but not all drugs in this section, but we include the interaction because the drugs in this section are similar to one another. We have also included potentially serious interactions listed in the drug’s FDA-approved professional package insert or in published medical journal articles. There may be other drugs, especially those in the families of drugs listed below, that also will react with this drug to cause severe adverse effects. Make sure to tell your doctor and pharmacist the drugs you are taking and tell them if you are taking any of these interacting drugs:

aminobenzoate, COUMADIN, DILANTIN, GLUCOPHAGE, GLUCOVANCE, HIPREX, METAGLIP, metformin, methenamine, methotrexate, ORINASE, phenytoin, thiopental, tolbutamide, TREXALL DOSE PACK, UREX, warfarin.

Adverse Effects [top]

Call your doctor immediately if you experience:

  • increased sensitivity of skin to the sun (increased sunburn)
  • skin rash or red, itching, blistering, or peeling skin
  • aching joints and muscles
  • difficulty swallowing
  • fever
  • pale skin
  • sore throat
  • abnormal bleeding or bruising
  • abnormal tiredness or weakness
  • yellow eyes or skin
  • lower back pain
  • increased thirst
  • difficulty urinating
  • blood in urine
  • painful urination
  • greatly increased or decreased frequency of urination
  • severe abdominal or stomach cramps
  • watery and severe diarrhea (may be bloody)
  • mood or mental changes
  • swelling of neck
  • confusion, hallucinations
  • loss of appetite

Call your doctor if these symptoms continue:

  • diarrhea
  • dizziness
  • headache
  • tiredness
  • loss of appetite
  • nausea or vomiting

Periodic Tests[top]

Ask your doctor which of these tests should be done periodically while you are taking this drug:

  • complete blood count
  • urinalysis

last reviewed April 30, 2021