This medication is used to treat a wide variety of bacterial infections. It is also used to treat a certain type of pneumonia (pneumocystis pneumonia) in patients with a weakened immune system. This medication is a combination of 2 antibiotics: sulfamethoxazole and trimethoprim. It works by stopping the growth of bacteria and the pneumocystis fungus.

This medication should not be used by children less than 2 months of age due to the risk of serious side effects.

This medication is given by injection into a vein as directed by your doctor. It is given by slow infusion over 60 to 90 minutes. The dosage is based on your medical condition, weight, and response to treatment.

If you are giving this medication to yourself at home, learn all preparation and usage instructions from your health care professional. Before using, check this product for particles or discoloration. If either is present, do not use the liquid. Learn how to store and discard medical supplies safely.

Drink plenty of fluids while taking this medication to lower the unlikely risk of kidney stones forming, unless your doctor advises you otherwise.

For the best effect, use this antibiotic at evenly spaced times. To help you remember, use this medication at the same time(s) every day.

Continue to use this medication for the full time prescribed, even if symptoms disappear after a few days. Stopping the medication too early may result in a return of the infection.

Tell your doctor if your condition lasts or gets worse.

Nausea, vomiting, diarrhea, loss of appetite, and pain/redness/swelling at the injection site may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly.

Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor right away if you have any serious side effects, including:

• muscle weakness
• mental/mood changes
• signs of kidney problems (such as change in the amount of urine, blood in the urine)
• extreme drowsiness
• signs of low blood sugar (such as sudden sweating, shaking, fast heartbeat, hunger, blurred vision, dizziness, or tingling hands/feet)

Get medical help right away if you have any very serious side effects, including:

• headache that doesn't go away
• neck stiffness
• seizures
• slow/irregular heartbeat

This medication may rarely cause a severe intestinal condition due to a bacteria called C. difficile. This condition may occur during treatment or weeks to months after treatment has stopped. Tell your doctor right away if you develop:

• diarrhea that doesn't stop
• abdominal or stomach pain/cramping
• blood/mucus in your stool

If you have these symptoms, do not use anti-diarrhea or opioid products because they may make symptoms worse.

Use of this medication for prolonged or repeated periods may result in oral thrush or a new yeast infection. Contact your doctor if you notice white patches in your mouth, a change in vaginal discharge, or other new symptoms.

This medication may rarely cause serious (possibly fatal) allergic reactions and other side effects such as a severe peeling skin rash (such as Stevens-Johnson syndrome), blood disorders (such as agranulocytosis, aplastic anemia), liver damage, or lung injury. If you notice any of the following, get medical help right away:

• sore throat or fever that doesn't go away
• cough that doesn't go away
• nausea/vomiting that doesn't stop
• skin rash/blisters
• itching/swelling (especially of the face/tongue/throat)
• new or worsening lymph node swelling
• severe dizziness
• paleness
• chest pain
• joint pain/aches
• trouble breathing
• easy bleeding/bruising
• yellowing eyes or skin
• unusual tiredness
• dark urine

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Before using this medication, tell your doctor or pharmacist if you are allergic to sulfamethoxazole or trimethoprim; or to sulfa medications; or if you have any other allergies. This product may contain inactive ingredients (such as benzyl alcohol or propylene glycol found in some brands), which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

• kidney disease
• liver disease
• certain blood disorders (such as porphyria, anemia due to folate vitamin deficiency)
• history of blood disorders caused by trimethoprim or sulfa medications
• vitamin deficiency (folate or folic acid)
• severe allergies
• asthma
• decreased bone marrow function (bone marrow suppression)
• a certain metabolic disorder (G6PD deficiency)
• underactive thyroid
• mineral imbalances (such as high level of potassium or low level of sodium in the blood)

This medication may cause live bacterial vaccines (such as typhoid vaccine) to not work well. Tell your health care professional that you are using this medication before having any immunizations/vaccinations.

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

This medication may make you more sensitive to the sun. Limit your time in the sun. Avoid tanning booths and sunlamps. Use sunscreen and wear protective clothing when outdoors. Get medical help right away if you get sunburned or have skin blisters/redness.

If you have diabetes, this product may affect your blood sugar. Check your blood sugar regularly as directed and share the results with your doctor. Tell your doctor right away if you have symptoms of low blood sugar (see Side Effects section). Your doctor may need to adjust your diabetes medication, exercise program, or diet.

Older adults may be more sensitive to the side effects of this drug, especially skin reactions, blood disorders, easy bleeding/bruising, and a high potassium blood level.

Patients with AIDS may be more sensitive to the side effects of this drug, especially skin reactions, fever, and blood disorders.

Tell your doctor if you are pregnant or plan to become pregnant. You should not become pregnant while using sulfamethoxazole/trimethoprim. This medication may harm an unborn baby. If you become pregnant, talk to your doctor right away about the risks and benefits of this medication.

This drug passes into breast milk. This drug may have undesirable effects on infants who are ill or premature or have certain disorders (jaundice, high blood levels of bilirubin, G6PD deficiency). Breastfeeding is not recommended for infants with these conditions. Consult your doctor before breastfeeding.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Some products that may interact with this drug include:

• "blood thinners" (such as warfarin)
• dofetilide
• methenamine
• methotrexate

This medication may interfere with certain lab tests, possibly causing false test results. Make sure lab personnel and all your doctors know you use this drug.

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669. Symptoms of overdose may include: severe nausea/vomiting/diarrhea, severe dizziness or drowsiness, mental/mood changes.

If you are using this drug for a long time, lab and/or medical tests (such as complete blood count, kidney function, potassium blood level, cultures) should be done while you are using this medication. Keep all medical and lab appointments. Consult your doctor for more details.

It is important to get each dose of this medication as scheduled. If you miss a dose, ask your doctor or pharmacist right away for a new dosing schedule. Do not double the dose to catch up.

Consult the product instructions and your pharmacist for storage details. Keep all medications away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.