Sulfisoxazole (Oral)

While there are many infections for which sulfisoxazole is an ideal treatment, it cannot be used to treat cold, flu, or other similar viral infections.


As a sulfonamide antibiotic, sulfisoxazole contains synthetic bacteriostatic antibiotics that can be used as a wide spectrum treatment for a variety of gram-positive and gram-negative bacterial agents. Some strains have shown to be resistant to this treatment, however. This class of drug acts to inhibit the production of bacteria by blocking p-aminobenzoic acid from developing in the folic acid metabolism cycle. The treatment is best taken orally, as this method allows for the sulfonamides to be absorbed by the tissue and distributed throughout the body.

Sulfisoxazole works by affecting enzyme dihydropteroate synthetase. The treatment inhibits the condensation of pteridine with para-aminobenzoic acid (PABA), which in turn prevents bacterial synthesis of dihydrofolic acid.

Commonly prescribed brand names for sulfisoxazole are Gantrisin Pediatric and Truxazole. The drug is available in tablet, syrup, or suspension.

Conditions treated:

  • Urinary tract infections
  • Meningococcal meningitis
  • Acute otitis media
  • Conjunctivitis
  • Nocardiosis
  • Chancroid
  • Toxoplasmosis
  • Malaria
  • Other bacterial infections

Type of medicine:

  • Anti-Infective
  • Sulfonamide

Side Effects:

Below are listed the most commonly experienced side effects; however, this isn't an exhaustive list and other symptoms may develop. Any negative effects produced by the sulfisoxazole treatment should be reported to the patient's doctor. Side effects that are experienced to a high degree of severity or emerge frequently may require immediate medical attention, so the patient should be urged to seek medical attention as soon as possible. The development of the listed side effects may indicate an allergic reaction or other incompatibility with the drug. By reporting the experienced side effects, the patient may be able to receive additional treatment to alleviate the severity of the side effects.

The most commonly observed side effects include:

  • Anxiety
  • Blurred vision
  • A change in menstrual periods
  • Chills
  • Cold sweats
  • Coma
  • Confusion
  • Pale or cool skin
  • Inhibited sexual performance in male patients
  • Depression
  • Lightheadedness
  • Puffy or dry skin
  • Increased heart rate
  • Headaches
  • Excessive hunger
  • Agitation or nervousness
  • Nightmares
  • Seizures
  • Trembling or shakiness
  • Speech changes, such as slurring
  • Swelling at the front of the neck
  • Excessive tiredness or weariness
  • Unexplained weight gain

Other side effects were reported but at an unreported rate of frequency. It's therefore unknown how likely the following side effects are to occur:

  • Abdominal pain, including stomach discomfort, cramps or tenderness
  • Agitation
  • Pain in the back, legs, or stomach
  • Bleeding of the gums or under the skin
  • Vision changes, including blindness
  • Blisters
  • Peeling, or loosening of the skin
  • Bloating
  • Cloudy or bloody urine
  • Stools that appear black, bloody, or tarry
  • Bluing of the skin, lips, palms, fingernails, or nail beds
  • Burning sensation in the face or mouth
  • Feelings of burning in the skin, or tingling, numbness, or itching
  • Sudden colorblindness, especially the inability to see blue or yellow
  • Chest pain
  • Chills
  • Clay colored stools
  • Balance problems, including clumsiness
  • Constipation
  • Auditory hallucinations, including a ringing or buzzing in the ears
  • Coughing or a feeling of hoarseness
  • Cracked, dry skin
  • Dark urine
  • Changes in the ability to urinate, including frequency and volume of urine
  • Diarrhea, which may be especially watery or bloody
  • Pain during urination
  • Difficult breathing or swallowing
  • Feeling dizzy or lightheaded
  • Drowsiness
  • Enlarged salivary glands
  • Fainting
  • Fast heartbeat, which may include heavy pounding or an irregular rhythm
  • General feeling of discomfort
  • Feeling cold
  • Fever
  • Swelling
  • Hair loss
  • Headaches
  • Hearing loss
  • Hives or welts
  • Unexplained hostility or irritability
  • Sudden sensitiveness to sunlight
  • Excessive thirst
  • Indigestion
  • Inflammation of the joints
  • Large, hive-like welts on the face, tongue, eyelids, lips, throat, hands, legs, feet, or on the sex organs
  • Lethargy
  • Loss of appetite or unexplained weight loss
  • Loss of body heat, strength, or energy
  • Pain in the lower back or sides
  • Muscle pain, including aches, weakness, or twitching
  • Nose bleeds
  • Pain in the stomach or abdomen, which radiates to the side or back
  • Pale skin, or pinpoint spots on the skin, which may appear red or purple in color
  • Swelling or puffiness around the face, including the lips, eyes, or tongue
  • Rapid heart rate
  • Sudden or fast weight gain
  • Rash
  • Red lesions in the skin, which may have a purplish color
  • Eyes that become red and irritated
  • Irritated skin
  • Scaly skin or severe sunburn
  • Shaky, uncertain walk
  • Shivering
  • Shortness of breath
  • Ulcers, sores, or white spots on the lips or in the mouth
  • Sores, welts, or blisters present anywhere on the body
  • Stupor
  • Swelling of the face or limbs
  • Swollen or painful glands, particularly the lymph glands
  • Thick bronchial secretions
  • Difficulty breathing, including a sensation of tightness in the chest
  • Foul or unpleasant breath odor
  • Unexplained or unusual bleeding or bruising
  • Unexplained weight changes
  • Pain in the upper right abdomen
  • Vomiting, which may be bloody or appear to look like coffee grounds
  • Weakness of the hands or feet
  • Wheezing
  • Yellow eyes or skin

Additionally, the patient may experience feelings of confusion, excessive gas, fear, paranoia, or hallucinations. Unusual behavior, mood changes, and a lack of emotions may also result. Although these side effects are rare, the patient should report experiencing any of them to his or her doctor.


As sulfisoxazole is given in tablet form and can be taken at home, the administering by a trained caregiver is not necessary. However, the patient should make sure to adhere to his or her physician's instructions. Sulfisoxazole should not be given to an infant under two months of age unless explicitly prescribed by the infant's caregiver. Serious side effects may result for patients in this age group.

Otherwise, the dosage varies, based upon the condition for which it's used as a treatment. For cystitis, patients should take 1 to 2 grams every six hours for three to seven days. The dosage for inclusion conjunctivitis and Trachoma is similar, except that treatment should be continued for 21 days. In treating malaria, a higher dosage may be required. Patients are directed to take 2 grams orally for 7 to 10 days, though sulfisoxazole is only used as a part of chloroquine-resistant Plasmodium falciparum therapy.

Nocardiosis is also treated with 2 gram doses, though a dose should be taken every 4 to 6 hours for a minimum of six months. Patients with compromised immune systems may have to continue treatment for a year, or possibly longer.

In treating Otitis Media, the 2 gram dosage should be taken every six hours for 10 to 14 days.

Pelvic Inflammatory Disease is treated with 500 mg of sulfisoxazole every six hours for a term of 21 days. The drug should be taken in conjunction with ceftriaxone for best results.

Two grams should be taken every 6 hours to treat cases of pyelonephritis and that treatment cycle should last 14 days. Similarly, the dosage required to treat toxoplasmosis is also 2 grams, taken every six hours. In this case, however, the drug should be coupled with doses of pyrimethamine. The first pyrimethamine dose should be 75 mg, which is to be followed with a 25 mg dose daily, also taken orally. Additionally, bone marrow toxicity can be prevented by adding 3 to 9 mg of folinic acid, taken two to three times per week. The drug treatments for toxoplasmosis should continue for two to four months.

Treating meningitis - meningococcal, meningitis - haemophilus influenza, and chancroid requires a dose of two grams given orally every six hours. For meningitis - meningococcal and meningitis - haemophilus influenza, the treatment cycle is 14 days, while chancroid only requires a cycle of seven days.

In treating chancroid, the patient's sexual partners should also be notified and examined for infection. The patients should also be tested for gonococcus and syphilis. The Centers for Disease Control and Prevention (CDC) has determined that sulfisoxazole is no longer the preferred treatment for chancroid and currently recommends other therapies in its place.

Pediatric doses of sulfisoxazole for children older than two months are as follows:

Chlamydia infection - 100 mg/kg/day divided into individual doses to be administered every six hours. No more than two grams per day should be given.

Toxoplasmosis - In treating a congenital condition, the child should be given half of the 24-hour dose, which is a maximum of 6 grams per day. Maintenance doses are 150 mg/kg/day or 4 g/m2/day, divided into four to six doses. This treatment should be administered in conjunction with pyrimethamine.

Pelvic Inflammatory Disease - Divided into six hour doses, 100 mg/kg should be administered each day in combination with ceftriaxone.

As is the case in treating any condition with sulfisoxazole, the dosage size and treatment cycle can be adjusted, according to the severity and the nature of the infection.

Major Drug Interactions

There's no way to tell how some drugs will interact with others that the patient may be taking, so it's vital that the patient and doctor openly discuss current and past medications. In addition to prescription medications, the patient must tell the doctor about any other medications he or she may be taking. This includes nonprescription drugs, like aspirin, ibuprofen, over the counter sleeping pills, or medicine for heartburn relief. Additionally, the patient should make sure his or her doctor is aware of any vitamins or herbal remedies being used. Indulging in alcohol and narcotic use should also be discussed and discontinued, during treatment.

Although this is not a complete list, below are the drugs most commonly known to cause adverse reactions with sulfisoxazole. If the patient is specifically taking these drugs, he or she must notify their doctor, before beginning sulfisoxazole treatments.

  • Acidophilus Probiotic Blend (lactobacillus acidophilus)
  • Advair Diskus (fluticasone / salmeterol)
  • Amoxil (amoxicillin)
  • Balanced B-100 (multivitamin)
  • Co-trimoxazole (sulfamethoxazole / trimethoprim)
  • Demerol (meperidine)
  • DuoNeb (albuterol / ipratropium)
  • Fish Oil (omega-3 polyunsaturated fatty acids)
  • Fish Oil Ultra (omega-3 polyunsaturated fatty acids)
  • Singulair (montelukast)
  • Spiriva (tiotropium)
  • Symbicort (budesonide/formoterol)
  • Tessalon (benzonatate)
  • Ventolin (albuterol)
  • Ventolin HFA (albuterol)
  • Vitamin D3 (cholecalciferol)

Any changes of medications should be discussed with the attending doctor in advance. The effects of starting, stopping, or changing the dosages of any medication can be unpredictable, so the patient is urged not to act without the doctor's guidance. Such changes can be safely done with the guidance of a trained caregiver.


Equally important is a frank discussion of the patient's medical history, particularly focusing on current and past health conditions. Often, a new drug treatment can interact negatively with a medical condition, compromising the patient's overall health status. This includes discussing any allergies of which the patient may be aware, especially allergies to certain foods, dyes, preservatives, or chemicals.

Additionally, sulfisoxazole may affect the patient adversely or may not be an effective treatment, if she or he has been diagnosed with any of the following medical conditions:

  • Hematologic toxicity
  • Hypersensitivity reactions
  • Liver disease
  • Porphyria
  • Renal dysfunction
  • Colitis
  • Crystalluria
  • Hemodialysis
  • Urinary obstruction

Sulfisoxazole has been classified a class C pregnancy drug by the U.S. Food and Drug Administration and evidence of teratogenicity has developed in subjects during animal testing studies. While there is no data concerning human pregnancies, it's recommended that sulfisoxazole only be used as a treatment where the benefits of the drug therapy outweigh the risks to the unborn baby. Women nearing their due date should not consider sulfisoxazole as a treatment.

As a sulfonamide, sulfisoxazole crosses the placenta and achieves balance with the maternal serum within two to three hours. This has the effect of increasing free sulfisoxazole levels, which can cause hyperbilirubinemia, jaundice, and kernicterus in newborns. For this reason, sulfisoxazole shouldn't be prescribed to pregnant women nearing term. Earlier in the pregnancy, the fetus can dispose of excess levels of sulfisoxazole through the placenta's natural circulation process.

While there is no concrete data on the effects of sulfisoxazole playing a role in congenital birth defects, some studies do point to reasons for caution. In one study, 458 children who were found to have been born with congenital birth defects were more often born to women who had taken sulfisoxazole. In another retrospective research project, it was found that mothers taking sulfonamides during their first and second trimesters more often gave birth to children with oral clefts.

A Michigan Medicaid study looked at the correlation between the drug combination trimethoprim-sulfamethoxazole (TMP-SMX) and congenital birth defects. In the first study, 1,116 of 104,000 pregnant women received the TMP-SMX treatment. Out of those 1,116 women, 83 total defects, including 13 cardiovascular defects, were found in their offspring. The second study consisted of 2,296 of 229,000 pregnant women receiving the TMP-SMX treatment. In that study, a total of 126 birth defects were observed with 37 cardiovascular defects. While sulfonamides administered as a sole treatment appear to be safe for pregnant women, combining the drug with other medications may cause birth defects. This is especially true in prescribing sulfonamides near term for pregnant women.

In breastfeeding, sulfisoxazole poses a very low risk to infants, because it's an extremely water soluble substance and establishes a low concentration in breast milk. Studying the rate at which sulfisoxazole is found in breast milk, the ratio was found to be as low as 0.06. In a recent study, the amount of sulfisoxazole found in breast milk, just 48 hours after administering a 4 gram dose of the drug, was 0.45%. Even though the rate at which sulfisoxazole is excreted into breast milk is low, the manufacturer advises against breastfeeding while taking the medication. The American Academy of Pediatrics believes breastfeeding is safe, while the mother is taking sulfisoxazole, if the infant is healthy and was carried full term. However, infants under two months of age should not be exposed to breast milk contaminated with sulfisoxazole, as there can be a risk of developing kernicterus.


Sulfisoxazole can be stored at room temperature in a cool, dry place. It should be kept in a closed container, away from sources of heat, moisture, or direct sunlight. Do not freeze.

Sulfisoxazole should also be kept in a place out of reach of children.

Once the medication has passed its expiration date, it should be disposed of immediately. Patients should consult a doctor on the proper method for disposing of this or any expired medications.


Sulfisoxazole is an efficient treatment for many kinds of bacterial infections and may be the best choice for patients suffering from an infection. As is the case with most drugs, there can be adverse reactions, particularly where the patient fails to openly reveal his or her medication use and past medical history. Certain conditions and some drugs can instigate a negative or harmful reaction once sulfisoxazole is introduced to the body chemistry, and that should be the primary concern for the patient and doctor. There may be unlisted reactions to certain foods or to alcohol or tobacco products, while on sulfisoxazole. The patient should discuss any concerns that arise with their doctor to ensure maximum effectiveness of this drug treatment and to reduce the risks of a harmful interaction. By working together and establishing a treatment plan that also establishes dietary and physical fitness rules for the patient, the best results can be achieved through administering sulfisoxazole to fight infection.

Last Reviewed:
December 26, 2017
Last Updated:
April 05, 2018
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