Some commonly used brand names are:

In the U.S.—

In Canada—

Other commonly used names are: Cotrimazine Cotrimoxazole SMZ-TMP

• Antibacterial, systemic --Sulfadiazine and Trimethoprim; Sulfamethoxazole and Trimethoprim
• Antiprotozoal --Sulfamethoxazole and Trimethoprim

Sulfonamide (sul-FON-ah-mide) and trimethoprim combinations are used to prevent and treat infections. Sulfadiazine and trimethoprim combination is used to treat urinary tract infections. Sulfamethoxazole and trimethoprim combination is used to treat infections, such as bronchitis, middle ear infection, urinary tract infection, and traveler's diarrhea. It is also used for the prevention and treatment of Pneumocystis carinii pneumonia (PCP). These medicines will not work for colds, flu, or other virus infections. They may also be used for other conditions as determined by your doctor.

Sulfonamide and trimethoprim combinations are available only with your doctor's prescription, in the following dosage forms:

Oral
• Sulfadiazine and Trimethoprim
  • Oral suspension (Canada)
  • Tablets (Canada)
• Sulfamethoxazole and Trimethoprim
  • Oral suspension (U.S. and Canada)
  • Tablets (U.S. and Canada)

Parenteral
• Sulfamethoxazole and Trimethoprim
  • Injection (U.S. and Canada)

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 sulfonamide and trimethoprim combinations, 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], methazolamide [e.g., Neptazane]), or trimethoprim (e.g., Trimpex). Also tell your health care professional if you are allergic to any other substances, such as foods, preservatives (e.g., sulfites), or dyes.

Pregnancy—Sulfamethoxazole and trimethoprim combination has not been reported to cause birth defects or other problems in humans. However, studies in mice, rats, and rabbits have shown that some sulfonamides cause birth defects, including cleft palate and bone problems. Studies in rabbits have also shown that trimethoprim causes birth defects, as well as a decrease in the number of successful pregnancies. Sulfonamides are not recommended for use at the time of labor and delivery because these medicines may cause unwanted effects in the baby.

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

Children—Sulfadiazine and trimethoprim combination should not be given to infants less than 3 months of age. Sulfamethoxazole and trimethoprim combination should not be given to infants less than 2 months of age unless directed by the child's doctor. These combinations may cause unwanted effects. In special situations, sulfamethoxazole and trimethoprim combination may be given to infants less than 2 months of age.

Older adults—Elderly people are especially sensitive to the effects of sulfonamide and trimethoprim combinations. 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 sulfonamide and trimethoprim combinations, it is especially important that your health care professional know 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
• 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 sulfonamide and trimethoprim combinations with these medicines may increase the chance of side effects affecting the liver

• Acetohydroxamic acid (e.g., Lithostat) 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)—Use of sulfonamide and trimethoprim combinations with these medicines may increase the chance of side effects affecting the blood

• Anticoagulants (blood thinners) or
• Digoxin (e.g., Lanoxin)
• Ethotoin (e.g., Peganone) or
• Mephenytoin (e.g., Mesantoin) or
• Methotrexate (e.g., Mexate) or
• Phenytoin (e.g., Dilantin)—Use of sulfonamide and trimethoprim combinations 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 sulfonamide and trimethoprim combinations may increase the chance of side effects affecting the blood and/or the side effects of the oral antidiabetics

• Methenamine (e.g., Mandelamine)—Use of methenamine with sulfonamide and trimethoprim combinations may increase the chance of side effects of the sulfonamide

• Methyldopa (e.g., Aldomet)—Use of methyldopa with sulfonamide and trimethoprim combinations may increase the chance of side effects affecting the liver and/or the blood

• 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

Sulfadiazine and trimethoprim combination should not be given to infants less than 3 months of age, and sulfamethoxazole and trimethoprim combination should not be given to infants less than 2 months of age unless directed by the child's doctor. These medicines may cause unwanted effects in the baby. In special situations, sulfamethoxazole and trimethoprim combination may be given to infants less than 2 months of age.

Sulfonamide and trimethoprim combinations 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.

The number of tablets or teaspoonfuls of suspension that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are taking sulfonamide and trimethoprim combinations.

For sulfadiazine and trimethoprim combination
• For oral dosage forms (suspension, tablets):
  • For bacterial infections:
    • Adults and teenagers—820 milligrams (mg) of sulfadiazine and 180 mg of trimethoprim once a day.
    • Infants less than 3 months of age—Use is not recommended.
    • Infants 3 months of age and older and children up to 12 years of age—Dose is based on body weight. The usual dose is 7 mg of sulfadiazine and 1.5 mg of trimethoprim per kilogram (kg) (3.2 mg of sulfadiazine and 0.7 mg of trimethoprim per pound) of body weight every twelve hours.

For sulfamethoxazole and trimethoprim combination
• For oral dosage forms (suspension, tablets):
  • For bacterial infections:
    • Adults and children 40 kilograms (kg) of body weight (88 pounds) and over—800 milligrams (mg) of sulfamethoxazole and 160 mg of trimethoprim every twelve hours.
    • Infants less than 2 months of age—Use is not recommended.
    • Infants 2 months of age and older and children up to 40 kg of weight (88 pounds)—Dose is based on body weight. The usual dose is 20 to 30 mg of sulfamethoxazole and 4 to 6 mg of trimethoprim per kg (9.1 to 13.6 mg of sulfamethoxazole and 1.8 to 2.7 mg of trimethoprim per pound) of body weight every twelve hours.
  • For the treatment of Pneumocystis carinii pneumonia (PCP):
    • Adults and children older than 2 months—Dose is based on body weight. The usual dose is 18.75 to 25 mg of sulfamethoxazole and 3.75 to 5 mg of trimethoprim per kg (8.5 to 11.4 mg of sulfamethoxazole and 1.7 to 2.3 mg of trimethoprim per pound) of body weight every six hours.
  • For the prevention of Pneumocystis carinii pneumonia (PCP):
    • Adults and teenagers—800 mg of sulfamethoxazole and 160 mg of trimethoprim once a day.
    • Infants and children 4 weeks of age and older—Dose is based on body size and must be determined by your doctor. There are several dosing regimens available that your doctor may choose from. One dosing regimen is 375 mg of sulfamethoxazole and 75 mg of trimethoprim per square meter of body surface two times a day, three times a week on consecutive days (e.g., Monday, Tuesday, Wednesday).
• For injection dosage form:
  • For bacterial infections:
    • Adults and children older than 2 months—The usual total daily dose is 40 to 50 mg of sulfamethoxazole and 8 to 10 mg of trimethoprim per kg (18.2 to 22.7 mg of sulfamethoxazole and 3.6 to 4.5 mg of trimethoprim per pound) of body weight. This total daily dose may be divided up and injected into a vein every six, eight, or twelve hours.
    • Infants less than 2 months of age—Use is not recommended.
  • For the treatment of Pneumocystis carinii pneumonia (PCP):
    • Adults and children older than 2 months—The usual dose is 18.75 to 25 mg of sulfamethoxazole and 3.75 to 5 mg of trimethoprim per kg (8.5 to 11.4 mg of sulfamethoxazole and 1.7 to 2.3 mg of trimethoprim per pound) of body weight. This is injected into a vein every six hours.
    • Infants less than 2 months of age—Use is not recommended.

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 form 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.

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.

Sulfonamide and trimethoprim combinations 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.

Sulfonamide and trimethoprim combinations 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 and 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.

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 or stomach tenderness;  anxiety;  blood in urine;  bluish fingernails, lips, or skin;  confusion;  diarrhea (watery and severe), which may also be bloody;  difficult breathing;  drowsiness;  fever;  general feeling of illness;  greatly increased or decreased frequency of urination or amount of urine;  hallucinations;  headache, severe;  increased thirst;  lower back pain;  mental depression;  muscle pain or weakness ;  nausea;  nervousness;  pain at site of injection;  pain or burning while urinating;  seizures (convulsions);  stiff neck and/or back;  swelling of front part of neck 
  
  

  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 using 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;  mouth sores or swelling of the tongue;  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.

Once a medicine has been approved for marketing for a certain use, experience may show that it is also useful for other medical problems. Although these uses are not included in product labeling, sulfamethoxazole and trimethoprim combination is used in certain patients for the following medical conditions:

• Bile infections
• Bone and joint infections
• HIV-related infections in Africa
• Sexually transmitted diseases, such as gonorrhea
• Sinus infections
• Toxoplasmosis (prevention of)
• Urinary tract infections (prevention of)
• Whipple's disease

Other than the above information, there is no additional information relating to proper use, precautions, or side effects for these uses.