Sulfamethoxazole and trimethoprim is a combination antibiotic used to treat ear infections, urinary tract infections, bronchitis, traveler's diarrhea, shigellosis, and Pneumocystis jiroveci pneumonia.

Sulfamethoxazole and trimethoprim may also be used for purposes not listed in this medication guide.

Use only as directed. Tell your doctor if you use other medicines or have other medical conditions or allergies.

Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.

Sulfamethoxazole and trimethoprim oral is taken by mouth.

Shake the oral suspension (liquid). Measure a dose with the supplied measuring device (not a kitchen spoon).

Sulfamethoxazole and trimethoprim injection is given in a vein. Be sure you understand how to properly mix this medicine with a liquid (diluent) and how to store the mixture. Ask your doctor or pharmacist if you don't understand how to use an injection.

Prepare an injection only when you are ready to give it. Call your pharmacist if the medicine looks cloudy, has changed colors, or has particles in it.

Mixed medicine must be used within 2 to 6 hours depending on the amount of diluent in the mixture. Follow your doctor's instructions. Do not refrigerate mixed medicine.

Do not reuse a needle or syringe. Place them in a puncture-proof "sharps" container and dispose of it following state or local laws. Keep out of the reach of children and pets.

Drink plenty of fluids to prevent kidney stones.

Antibiotic medicines can cause diarrhea. Tell your doctor if you have diarrhea that is watery or bloody.

Keep using this medicine even if your symptoms quickly improve. Skipping doses could make your infection resistant to medication. Sulfamethoxazole and trimethoprim will not treat a viral infection (flu or a common cold).

You may need blood and urine tests, and this medicine may be stopped based on the results.

Store at room temperature away from moisture, heat, and light. Do not refrigerate.

You should not use sulfamethoxazole and trimethoprim if you are allergic to sulfamethoxazole or trimethoprim, or if you have:

• severe liver disease;

• kidney disease that is not being treated or monitored;

• anemia (low red blood cells) caused by folic acid deficiency;

• a history of low blood platelets after taking trimethoprim or any sulfa drug; or

• if you take dofetilide.

May cause birth defects. Do not use if you are pregnant. Tell your doctor if you become pregnant.

Do not breastfeed.

This medicine should not be given to a child younger than 2 months old.

Tell your doctor if you have ever had:

• kidney or liver disease;

• a folate (folic acid) deficiency;

• asthma or severe allergies;

• HIV or AIDS;

• a thyroid disorder;

• malnourishment;

• alcoholism;

• an electrolyte imbalance (such as low blood sodium or high potassium);

• porphyria, or glucose-6-phosphate dehydrogenase (G6PD) deficiency; or

• if you use a blood thinner (such as warfarin) and you have routine "INR" or prothrombin time tests.

Use the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not use two doses at one time.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Overdose symptoms may include loss of appetite, vomiting, fever, blood in your urine, yellowing of your skin or eyes, confusion, or loss of consciousness.

If you use the injection form of sulfamethoxazole and trimethoprim, do not eat or drink anything that contains propylene glycol (an ingredient in many processed foods, soft drinks, and medicines). Dangerous effects could occur.

Sulfamethoxazole and trimethoprim could make you sunburn more easily. Avoid sunlight or tanning beds. Wear protective clothing and use sunscreen (SPF 30 or higher) when you are outdoors.

Get emergency medical help if you have signs of an allergic reaction (hives, cough, chest pain, shortness of breath, swelling in your face or throat) or a severe skin reaction (fever, sore throat, burning eyes, skin pain, red or purple skin rash with blistering and peeling).

Seek medical treatment if you have a serious drug reaction that can affect many parts of your body. Symptoms may include: skin rash, fever, swollen glands, joint pain, muscle aches, severe weakness, pale skin, unusual bruising, or yellowing of your skin or eyes.

Sulfamethoxazole and trimethoprim may cause serious side effects. Call your doctor at once if you have:

• severe stomach pain, diarrhea that is watery or bloody (even if it occurs months after your last dose);

• any skin rash, no matter how mild;

• yellowing of your skin or eyes;

• a seizure;

• new or unusual joint pain;

• increased or decreased urination;

• swelling, bruising, or irritation around the IV needle;

• increased thirst, dry mouth, fruity breath odor;

• new or worsening cough, fever, trouble breathing;

• high blood potassium--nausea, weakness, tingly feeling, chest pain, irregular heartbeats, loss of movement;

• low blood sodium--headache, confusion, problems with thinking or memory, weakness, feeling unsteady; or

• low blood cell counts--fever, chills, mouth sores, skin sores, easy bruising, unusual bleeding, pale skin, cold hands and feet, feeling light-headed or short of breath.

Common side effects of sulfamethoxazole and trimethoprim may include:

• nausea, vomiting, loss of appetite; or

• skin rash.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

You may need more frequent check-ups or medical tests if you also use medicine to treat depression, diabetes, seizures, or HIV.

Tell your doctor about all your current medicines. Many drugs can affect sulfamethoxazole and trimethoprim, especially:

• amantadine, digoxin, cyclosporine, indomethacin, leucovorin, methotrexate, procainamide, pyrimethamine;

• an "ACE inhibitor" heart or blood presure medication (benazepril, enalapril, lisinopril, quinapril, ramipril, and others); or

• a diuretic or "water pill".

This list is not complete and many other drugs may affect sulfamethoxazole and trimethoprim. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.