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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.
Sulfamethoxazole and trimethoprim
Generic name: sulfamethoxazole and trimethoprim (oral/injection) [ SUL-fa-meth-OX-a-zole-and-trye-METH-oh-prim ]
Brand names: Bactrim, Bactrim DS, SMZ-TMP DS, Sulfatrim Pediatric, Septra, . show all 18 brands Sulfatrim, Bethaprim, Cotrim, Uroplus, Uroplus DS, Cotrim DS, Septra I.V., Bactrim I.V., Bactrim Pediatric, Bethaprim Pediatric, Sulfatrim Suspension, Cotrim Pediatric, Septra DS
Dosage forms: intravenous solution (80 mg-16 mg/mL), oral suspension (200 mg-40 mg/5 mL), oral tablet (400 mg-80 mg; 800 mg-160 mg)
Drug class: Sulfonamides
Medically reviewed by Drugs.com on Aug 30, 2021. Written by Cerner Multum.
What is sulfamethoxazole and trimethoprim?
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.
Before taking this medicine
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;
- 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.
How should I use sulfamethoxazole and trimethoprim?
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.
What happens if I miss a dose?
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.
What happens if I overdose?
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.
What should I avoid while using sulfamethoxazole and trimethoprim?
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.
Sulfamethoxazole and trimethoprim side effects
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.
What other drugs will affect sulfamethoxazole and trimethoprim?
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.
People with a sulfa allergy typically need to avoid sulfonamide antibiotics (antibiotics containing sulfa), including:
- Septra and Bactrim (sulfamethoxazole-trimethoprim)
- Pediazole (erythromycin-sulfisoxazole)
Whether other nonantibiotic sulfa-containing drugs need to be avoided with sulfa allergy is unclear and considered on a case-by-case basis. Continue reading
- Can I drink alcohol when taking sulfamethoxazole / trimethoprim DS?
- What dose of co-trimoxazole is used in a patient with a UTI?
More about sulfamethoxazole / trimethoprim
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- Sulfamethoxazole/trimethoprim Intravenous (Advanced Reading)
- Sulfamethoxazole and Trimethoprim Injection
- Sulfamethoxazole and Trimethoprim Tablets
- Sulfamethoxazole and Trimethoprim Suspension
Related treatment guides
- Bacterial Infection
- Bacterial Skin Infection
Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.
Copyright 1996-2023 Cerner Multum, Inc. Version: 11.02.
Sulfamethoxazole-Trimethoprim – Uses, Side Effects, and More
This medication is a combination of two antibiotics: sulfamethoxazole and trimethoprim. It is used to treat a wide variety of bacterial infections (such as middle ear, urine, respiratory, and intestinal infections). It is also used to prevent and treat a certain type of pneumonia (pneumocystis-type).This medication should not be used by children less than 2 months of age due to the risk of serious side effects.This medication treats only certain types of infections. It will not work for viral infections (such as flu). Unnecessary use or misuse of any antibiotic can lead to its decreased effectiveness.
How to use sulfamethoxazole-trimethoprim oral
Take this medication by mouth, as directed by your doctor, with a full glass of water (8 ounces / 240 milliliters). If stomach upset occurs, take with food or milk. Drink plenty of fluids while taking this medication to lower the unlikely risk of kidney stones forming, unless your doctor advises you otherwise. Dosage is based on your medical condition and response to treatment.
For the best effect, take this antibiotic at evenly spaced times. To help you remember, take this medication at the same time(s) every day.
Continue to take this medication until the full prescribed amount is finished, even if symptoms disappear after a few days. Stopping it too early may allow bacteria to continue to grow, which may result in a relapse of the infection.
Tell your doctor if your condition lasts or gets worse.
Nausea, vomiting, diarrhea, and loss of appetite 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 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, paleness, joint pain/aches, trouble breathing, easy bleeding/bruising, yellowing eyes or skin, unusual fatigue, dark urine.
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 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 taking 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, 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. While there have been no reports of harm to healthy infants, 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). Breast-feeding is not recommended for infants with these conditions. Consult your doctor before breast-feeding.