SULFONAMIDES (Systemic)

Some commonly used brand names are:

In the U.S.—

  • Gantanol 3
  • Gantrisin 4
  • Thiosulfil Forte 2
  • Urobak 3

In Canada—

  • Apo-Sulfamethoxazole 3
  • Apo-Sulfisoxazole 4
  • Novo-Soxazole 4
  • Sulfizole 4

Note:

For quick reference, the following sulfonamides are numbered to match the corresponding brand names.

This information applies to the following medicines:
1. Sulfadiazine (sul-fa-DYE-a-zeen)§
2. Sulfamethizole (sul-fa-METH-a-zole)
3. Sulfamethoxazole (sul-fa-meth-OX-a-zole)§
4. Sulfisoxazole (sul-fi-SOX-a-zole)
† Not commercially available in Canada
‡ Generic name product may be available in the U.S.
§ Generic name product may be available in Canada

Category

  • Antibacterial, systemic—Sulfadiazine; Sulfamethoxazole; Sulfisoxazole
  • Antibacterial, urinary—Sulfamethizole
  • Antiprotozoal—Sulfamethoxazole; Sulfisoxazole

Description

Sulfonamides (sul-FON-a-mides) or sulfa medicines are used to treat infections. They will not work for colds, flu, or other virus infections.

Sulfonamides are available only with your doctor's prescription, in the following dosage forms:

  • Oral
  • Sulfadiazine
    • Tablets (U.S. and Canada)
  • Sulfamethizole
    • Tablets (U.S.)
  • Sulfamethoxazole
    • Tablets (U.S. and Canada)
  • Sulfisoxazole
    • Oral suspension (U.S.)
    • Syrup (U.S.)
    • Tablets (U.S. and Canada)

Before Using This Medicine

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For sulfonamides, the following should be considered:

Allergies—Tell your doctor if you have ever had any unusual or allergic reaction to sulfa medicines, furosemide (e.g., Lasix) or thiazide diuretics (water pills), oral antidiabetics (diabetes medicine you take by mouth), glaucoma medicine you take by mouth (for example, acetazolamide [e.g., Diamox], dichlorphenamide [e.g., Daranide], or methazolamide [e.g., Neptazane]). Also tell your health care professional if you are allergic to any other substances, such as foods, preservatives, or dyes.

Pregnancy—Studies have not been done in pregnant women. However, studies in mice, rats, and rabbits have shown that some sulfonamides cause birth defects, including cleft palate and bone problems. Sulfonamides are not recommended for use at the time of labor and delivery. These medicines may cause unwanted effects in the baby.

Breast-feeding—Sulfonamides pass into the breast milk. This medicine is not recommended for use during breast-feeding. It may cause liver problems, anemia, and other unwanted effects in nursing babies, especially those with glucose-6-phosphate dehydrogenase (G6PD) deficiency.

Children—Sulfonamides should not be given to infants under 2 months of age unless directed by the child's doctor, because they may cause unwanted effects.

Older adults—Elderly people are especially sensitive to the effects of sulfonamides. Severe skin problems and blood problems may be more likely to occur in the elderly. These problems may also be more likely to occur in patients who are taking diuretics (water pills) along with this medicine.

Other medicines—Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking sulfonamides, it is especially important that your health care professional knows if you are taking any of the following:

  • Acetaminophen (e.g., Tylenol) (with long-term, high-dose use) or
  • Amiodarone (e.g., Cordarone) or
  • Anabolic steroids (nandrolone [e.g., Anabolin], oxandrolone [e.g., Anavar], oxymetholone [e.g., Anadrol], stanozolol [e.g., Winstrol]) or
  • Androgens (male hormones) or
  • Antithyroid agents (medicine for overactive thyroid) or
  • Carbamazepine (e.g., Tegretol) or
  • Carmustine (e.g., BiCNU) or
  • Chloroquine (e.g., Aralen) or
  • Dantrolene (e.g., Dantrium) or
  • Daunorubicin (e.g., Cerubidine) or
  • Disulfiram (e.g., Antabuse) or
  • Divalproex (e.g., Depakote) or
  • Estrogens (female hormones) or
  • Etretinate (e.g., Tegison) or
  • Gold salts (medicine for arthritis) or
  • Hydroxychloroquine (e.g., Plaquenil) or
  • Mercaptopurine (e.g., Purinethol) or
  • Naltrexone (e.g., Trexan) (with long-term, high-dose use) or
  • Oral contraceptives (birth control pills) containing estrogens or
  • Other anti-infectives by mouth or by injection (medicine for infection) or
  • Phenothiazines (acetophenazine [e.g., Tindal], chlorpromazine [e.g., Thorazine], fluphenazine [e.g., Prolixin], mesoridazine [e.g., Serentil], perphenazine [e.g., Trilafon], prochlorperazine [e.g., Compazine], promazine [e.g., Sparine], promethazine [e.g., Phenergan], thioridazine [e.g., Mellaril], trifluoperazine [e.g., Stelazine], triflupromazine [e.g., Vesprin], trimeprazine [e.g., Temaril]) or
  • Plicamycin (e.g., Mithracin) or
  • Valproic acid (e.g., Depakene)—Use of sulfonamides with these medicines may increase the chance of side effects affecting the liver
  • Acetohydroxamic acid (e.g., Lithostat) or
  • Dapsone or
  • Furazolidone (e.g., Furoxone) or
  • Nitrofurantoin (e.g., Furadantin) or
  • Primaquine or
  • Procainamide (e.g., Pronestyl) or
  • Quinidine (e.g., Quinidex) or
  • Quinine (e.g., Quinamm) or
  • Sulfoxone (e.g., Diasone) or
  • Vitamin K (e.g., AquaMEPHYTON, Synkayvite)—Use of sulfonamides with these medicines may increase the chance of side effects affecting the blood
  • Anticoagulants (blood thinners) or
  • Ethotoin (e.g., Peganone) or
  • Mephenytoin (e.g., Mesantoin)—Use of sulfonamides with these medicines may increase the chance of side effects of these medicines
  • Antidiabetics, oral (diabetes medicine you take by mouth)—Use of oral antidiabetics with sulfonamides may increase the chance of side effects affecting the blood and/or the side effects of oral antidiabetics
  • Methenamine (e.g., Mandelamine)—Use of this medicine with sulfonamides may increase the chance of side effects of sulfonamides
  • Methotrexate (e.g., Mexate) or
  • Phenytoin (e.g., Dilantin)—Use of these medicines with sulfonamides may increase the chance of side effects affecting the liver and/or the side effects of these medicines
  • Methyldopa (e.g., Aldomet)—Use of methyldopa with sulfonamides may increase the chance of side effects affecting the liver and/or the blood

Other medical problems—The presence of other medical problems may affect the use of sulfonamides. Make sure you tell your doctor if you have any other medical problems, especially:

  • Anemia or other blood problems or
  • Glucose-6-phosphate dehydrogenase (G6PD) deficiency—Patients with these problems may have an increase in side effects affecting the blood
  • Kidney disease or
  • Liver disease—Patients with kidney and/or liver disease may have an increased chance of side effects
  • Porphyria—This medicine may bring on an attack of porphyria

Proper Use of This Medicine

Sulfonamides should not be given to infants less than 2 months of age unless directed by the patient's doctor because sulfonamides may cause serious unwanted effects.

Sulfonamides are best taken with a full glass (8 ounces) of water . Several additional glasses of water should be taken every day , unless otherwise directed by your doctor. Drinking extra water will help to prevent some unwanted effects of sulfonamides.

For patients taking the oral liquid form of this medicine:

  • Use a specially marked measuring spoon or other device to measure each dose accurately. The average household teaspoon may not hold the right amount of liquid.

To help clear up your infection completely, keep taking this medicine for the full time of treatment , even if you begin to feel better after a few days. If you stop taking this medicine too soon, your symptoms may return.

This medicine works best when there is a constant amount in the blood or urine. To help keep the amount constant, do not miss any doses. Also, it is best to take the doses at evenly spaced times day and night . If you need help in planning the best times to take your medicine, check with your health care professional.

Dosing—The dose of these medicines will be different for different patients. Follow your doctor's orders or the directions on the label . The following information includes only the average doses of these medicines. If your dose is different, do not change it unless your doctor tells you to do so.

  • For sulfadiazine
  • For tablet dosage form:
    • For bacterial or protozoal infections:
      • Adults and teenagers—2 to 4 grams for the first dose, then 1 gram every four to six hours.
      • Children up to 2 months of age—Use is not recommended.
      • Children 2 months of age and older—Dose is based on body weight. The usual dose is 75 milligrams (mg) per kilogram (kg) (34 mg per pound) of body weight for the first dose, then 37.5 mg per kg (17 mg per pound) of body weight every six hours, or 25 mg per kg (11.4 mg per pound) of body weight every four hours.
  • For sulfamethizole
  • For tablet dosage form:
    • For bacterial infections:
      • Adults and teenagers—500 milligrams (mg) to 1 gram every six to eight hours.
      • Children up to 2 months of age—Use is not recommended.
      • Children 2 months of age and older—Dose is based on body weight. The usual dose is 7.5 to 11.25 mg per kilogram (kg) (3.4 to 5.1 mg per pound) of body weight every six hours.
  • For sulfamethoxazole
  • For tablet dosage form:
    • For bacterial or protozoal infections:
      • Adults and teenagers—2 to 4 grams for the first dose, then 1 to 2 grams every eight to twelve hours.
      • Children up to 2 months of age—Use and dose must be determined by your doctor.
      • Children 2 months of age and older—Dose is based on body weight. The usual dose is 50 to 60 milligrams (mg) per kilogram (kg) (22.7 to 27.3 mg per pound) of body weight for the first dose, then 25 to 30 mg per kg (11.4 to 13.6 mg per pound) of body weight every twelve hours.
  • For sulfisoxazole
  • For suspension, syrup, or tablet dosage forms:
    • For bacterial or protozoal infections:
      • Adults and teenagers—2 to 4 grams for the first dose, then 750 milligrams (mg) to 1.5 grams every four hours; or 1 to 2 grams every six hours.
      • Children up to 2 months of age—Use and dose must be determined by your doctor.
      • Children 2 months of age and older—Dose is based on body weight. The usual dose is 75 mg per kilogram (kg) (34 mg per pound) of body weight for the first dose, then 25 mg per kg (11.4 mg per pound) of body weight every four hours, or 37.5 mg per kg (17 mg per pound) of body weight every six hours.

Missed dose—If you miss a dose of this medicine, take it as soon as possible. This will help to keep a constant amount of medicine in the blood or urine. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

Storage—To store this medicine:

  • Keep out of the reach of children.
  • Store away from heat and direct light.
  • Do not store the tablet form of this medicine in the bathroom, near the kitchen sink, or in other damp places. Heat or moisture may cause the medicine to break down.
  • Keep the oral liquid forms of this medicine from freezing.
  • Do not keep outdated medicine or medicine no longer needed. Be sure that any discarded medicine is out of the reach of children.

Precautions While Using This Medicine

It is very important that your doctor check your progress at regular visits . This medicine may cause blood problems, especially if it is taken for a long time.

If your symptoms do not improve within a few days, or if they become worse, check with your doctor.

Sulfonamides may cause blood problems. These problems may result in a greater chance of certain infections, slow healing, and bleeding of the gums. Therefore, you should be careful when using regular toothbrushes, dental floss, and toothpicks. Dental work should be delayed until your blood counts have returned to normal. Check with your medical doctor or dentist if you have any questions about proper oral hygiene (mouth care) during treatment.

Sulfonamides may cause your skin to be more sensitive to sunlight than it is normally. Exposure to sunlight, even for brief periods of time, may cause a skin rash, itching, redness or other discoloration of the skin, or a severe sunburn. When you begin taking this medicine:

  • Stay out of direct sunlight, especially between the hours of 10:00 a.m. and 3:00 p.m., if possible.
  • Wear protective clothing, including a hat. Also, wear sunglasses.
  • Apply a sun block product that has a skin protection factor (SPF) of at least 15. Some patients may require a product with a higher SPF number, especially if they have a fair complexion. If you have any questions about this, check with your health care professional.
  • Apply a sun block lipstick that has an SPF of at least 15 to protect your lips.
  • Do not use a sunlamp or tanning bed or booth.

If you have a severe reaction from the sun, check with your doctor .

This medicine may also cause some people to become dizzy. Make sure you know how you react to this medicine before you drive, use machines, or do anything else that could be dangerous if you are dizzy or are not alert . If this reaction is especially bothersome, check with your doctor.

Side Effects of This Medicine

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur:

More common

Itching; skin rash

Less common

Aching of joints and muscles; difficulty in swallowing; pale skin; redness, blistering, peeling, or loosening of skin; sore throat and fever; unusual bleeding or bruising; unusual tiredness or weakness; yellow eyes or skin

Rare

Abdominal or stomach cramps and pain (severe); abdominal tenderness; blood in urine; diarrhea (watery and severe), which may also be bloody; greatly increased or decreased frequency of urination or amount of urine; increased thirst; lower back pain; mood or mental changes; pain or burning while urinating; swelling of front part of neck

Note:

Some of the above side effects (severe abdominal or stomach cramps and pain, and watery and severe diarrhea, which may also be bloody) may also occur up to several weeks after you stop taking any of these medicines.

Also, check with your doctor as soon as possible if the following side effect occurs:

More common

Increased sensitivity of skin to sunlight

Other side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. However, check with your doctor if any of the following side effects continue or are bothersome:

More common

Diarrhea; dizziness; headache; loss of appetite; nausea or vomiting; tiredness

Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor.

Revised: 08/25/1995

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