Sulfamethoxazole and Trimethoprim

💊 What is Sulfamethoxazole and Trimethoprim used for?

• •Urinary tract infections caused by susceptible bacteria
• •Acute ear infection (acute otitis media) in children, caused by susceptible bacteria
• •Flare-ups of chronic bronchitis in adults, caused by susceptible bacteria
• •Shigellosis (a bowel infection causing enteritis) caused by susceptible Shigella bacteria
• •Treatment of documented Pneumocystis jirovecii pneumonia, and prevention of it in people who are immunosuppressed and at increased risk
• •Traveler's diarrhea in adults caused by susceptible enterotoxigenic E. coli

How it works

The label describes this as a synthetic antibacterial combination. It treats infections caused by bacteria that are susceptible to it. The label says it should only be used to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria. It does not treat viral infections such as the common cold.

How it is usually taken

• •This medicine is taken by mouth. Doses are set by your prescriber based on the infection, your age, your weight, and your kidney function. The label describes treatment lengths that range from about 5 days to 21 days, depending on the infection. The label says the medicine should be taken exactly as directed. Skipping doses or stopping before the full course is finished may make the treatment less effective and may increase the chance that bacteria become resistant. The label says to keep up your fluid intake to help prevent crystals and kidney stones. Follow the instructions from your prescriber or pharmacist.

Comes as

• •Tablets, 800 mg sulfamethoxazole and 160 mg trimethoprim (double strength, DS), white to off-white oval tablets
• •Tablets, 400 mg sulfamethoxazole and 80 mg trimethoprim

⚠️ Sulfamethoxazole and Trimethoprim side effects

🛑 Who should not take Sulfamethoxazole and Trimethoprim, and who should be careful

The label says not to take it if

• 🚨You have a known allergy or hypersensitivity to trimethoprim or sulfonamides.
• 🚨You have had drug-induced immune thrombocytopenia (low platelets) from trimethoprim or sulfonamides.
• 🚨You have documented megaloblastic anemia caused by folate deficiency.
• 🚨The patient is under 2 months of age.
• 🚨You have marked liver damage.
• 🚨You have severe kidney problems where kidney function cannot be monitored.
• 🚨You are taking dofetilide. The label lists this as a contraindication.

Tell your doctor before taking it if

• •Tell your prescriber about any past reactions to sulfa drugs, trimethoprim, or sulfonamides.
• •Tell your prescriber if you have had low platelets caused by these medicines in the past.
• •Tell your prescriber about any liver problems, kidney problems, or blood problems, including megaloblastic anemia from folate deficiency.
• •Tell your prescriber if you are pregnant, planning to become pregnant, or breastfeeding.
• •Tell your prescriber about all other medicines you take, including over-the-counter products and supplements.
• •The label says people who are elderly may have a higher chance of certain blood problems when using some diuretics along with this medicine.

🔀 Sulfamethoxazole and Trimethoprim with other medicines, food and alcohol

The label says to discuss these with your doctor or pharmacist

• •Diuretics, especially thiazides in elderly patients: the label says to avoid using them together because of an increased chance of low platelets with purpura.
• •Warfarin (a blood thinner): the label says prothrombin time and INR should be monitored because the medicine may prolong clotting time.
• •Phenytoin: the label says phenytoin levels may need to be monitored, since this medicine may raise phenytoin effects.
• •Methotrexate: the label says to avoid using them together.
• •Cyclosporine: the label says to avoid using them together because of reports of kidney toxicity in transplant patients.
• •Digoxin: the label says digoxin levels may need to be monitored, especially in elderly patients.
• •Indomethacin: the label says to avoid using them together.
• •Pyrimethamine: the label says to avoid using them together because of possible megaloblastic anemia.
• •Tricyclic antidepressants: the label says the response may need monitoring and the dose may need adjusting.
• •The label lists other interactions as well. Tell your prescriber or pharmacist about every medicine you take.

Alcohol and food

The label does not say.

🤰 Sulfamethoxazole and Trimethoprim in pregnancy and breastfeeding

Pregnancy

The label says there are no large, well-controlled studies in pregnant women. Some studies suggest that taking this medicine during early pregnancy may be linked to a higher risk of birth defects, including neural tube defects, heart defects, urinary tract defects, oral clefts, and club foot. The label also says this medicine may interfere with folic acid metabolism. It should be used during pregnancy only if the benefit to the patient justifies the potential risk to the fetus. Tell your prescriber right away if you become pregnant while taking it.

Breastfeeding

The label says small amounts of this medicine pass into breast milk, about 2 to 5% of the recommended daily dose for infants over 2 months old. Caution is advised when giving it to a breastfeeding woman, especially when the baby is jaundiced, ill, stressed, or premature, because of the potential risk of bilirubin displacement and kernicterus.

🗓️ Storage, missed doses and taking too much

Storage

Store at 20° to 25°C (68° to 77°F). Brief temperature changes to 15° to 30°C (59° to 86°F) are permitted, according to the label. Keep this medicine and all medicines out of the reach of children. The label notes that the unit dose package is not child resistant and is intended for institutional use only. Do not use if the blister is torn or broken.

If a dose is missed

The label does not say.

If too much is taken

The label says the single dose that could cause serious harm has not been reported. Signs of overdose with sulfonamides may include loss of appetite, colic, nausea, vomiting, dizziness, headache, drowsiness, and unconsciousness. Fever, blood in the urine, and crystals in the urine may also occur. Signs of overdose with trimethoprim may include nausea, vomiting, dizziness, headache, mental depression, confusion, and bone marrow depression. The label describes treatment such as stomach emptying, forcing fluids, and intravenous fluids. Seek medical help right away if an overdose is suspected.

🗒️ Questions to ask about Sulfamethoxazole and Trimethoprim

• Which bacterial infection am I being treated for, and how long will I need to take this medicine?
• Should I drink extra fluids while taking this medicine, and how much?
• What signs of a serious reaction should I watch for, and who should I call if they happen?
• Is this medicine safe to take with my other medicines, including my blood thinner or my blood pressure pills?
• Could this medicine affect my kidney function, and do I need tests during treatment?
• What should I do if diarrhea starts after I finish the medicine?

❓ Sulfamethoxazole and Trimethoprim: frequently asked questions