Generic name: sulfamethoxazole/trimethoprim [ sul-fa-meth-OX-a-zole, trye-METH-oh-prim ]
Drug class: Sulfonamides

Medically reviewed by Drugs.com. Last updated on Feb 13, 2024.

Uses for sulfamethoxazole/trimethoprim

Sulfamethoxazole and trimethoprim combination is used to treat intestinal or urinary tract infections. It is also used to treat Pneumocystis carinii pneumonia (PCP), a very serious kind of pneumonia. This type of pneumonia occurs more commonly in patients whose immune systems are not working normally, such as cancer patients, transplant patients, and patients with acquired immune deficiency syndrome (AIDS).

Sulfamethoxazole and trimethoprim combination is an antibiotic. It works by eliminating the bacteria that cause many kinds of infections. This medicine will not work for colds, flu, or other virus infections.

This medicine is available only with your doctor's prescription.

Before using sulfamethoxazole/trimethoprim

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 this medicine, the following should be considered:

Allergies

Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.

Pediatric

Appropriate studies performed to date have not demonstrated pediatric-specific problems that would limit the usefulness of sulfamethoxazole and trimethoprim combination in children older than 2 months of age. Safety and efficacy have not been established for infants less than 2 months of age.

Geriatric

Appropriate studies performed to date have not demonstrated geriatric-specific problems that would limit the usefulness of sulfamethoxazole and trimethoprim combination in the elderly. However, elderly patients are more likely to have age-related kidney or liver problems, which may require an adjustment in the dose for patients receiving sulfamethoxazole and trimethoprim combination.

Breast Feeding

Studies in women suggest that this medication poses minimal risk to the infant when used during breastfeeding.

Interactions with 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 receiving this medicine, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.

Using this medicine with any of the following medicines is not recommended. Your doctor may decide not to treat you with this medication or change some of the other medicines you take.

• Dofetilide
• Levomethadyl
• Methenamine

Using this medicine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

• Acecainide
• Acenocoumarol
• Ajmaline
• Amiloride
• Amiodarone
• Amitriptyline
• Amoxapine
• Aprindine
• Arsenic Trioxide
• Astemizole
• Azathioprine
• Azilsartan
• Azilsartan Medoxomil
• Azimilide
• Benazepril
• Bretylium
• Candesartan Cilexetil
• Captopril
• Ceritinib
• Chloral Hydrate
• Chloroquine
• Chlorpromazine
• Cholera Vaccine, Live
• Clarithromycin
• Desipramine
• Dibenzepin
• Digoxin
• Disopyramide
• Dolasetron
• Doxepin
• Dronedarone
• Droperidol
• Enalapril
• Enalaprilat
• Enflurane
• Eplerenone
• Eprosartan
• Erythromycin
• Flecainide
• Fluconazole
• Fluoxetine
• Foscarnet
• Fosinopril
• Fosphenytoin
• Gemifloxacin
• Glyburide
• Halofantrine
• Haloperidol
• Halothane
• Hydroquinidine
• Ibutilide
• Imipramine
• Irbesartan
• Isoflurane
• Isradipine
• Leucovorin
• Lidoflazine
• Lisinopril
• Lorcainide
• Losartan
• Mefloquine
• Mercaptopurine
• Methotrexate
• Moexipril
• Nortriptyline
• Octreotide
• Olmesartan Medoxomil
• Pentamidine
• Perindopril
• Phenytoin
• Pirmenol
• Porfimer
• Prajmaline
• Probucol
• Procainamide
• Prochlorperazine
• Propafenone
• Pyrimethamine
• Quinapril
• Quinidine
• Ramipril
• Risperidone
• Sapropterin
• Sematilide
• Sertindole
• Sotalol
• Spiramycin
• Spironolactone
• Sultopride
• Tedisamil
• Telithromycin
• Telmisartan
• Trandolapril
• Triamterene
• Trifluoperazine
• Trimipramine
• Valsartan
• Warfarin
• Zofenopril
• Zotepine

Using this medicine with any of the following medicines may cause an increased risk of certain side effects, but using both drugs may be the best treatment for you. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

• Acetohexamide
• Amantadine
• Aminolevulinic Acid
• Anisindione
• Didanosine
• Repaglinide
• Rifabutin
• Rosiglitazone
• Tolbutamide

Interactions with Food/Tobacco/Alcohol

Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.

Using this medicine with any of the following is usually not recommended, but may be unavoidable in some cases. If used together, your doctor may change the dose or how often you use this medicine, or give you special instructions about the use of food, alcohol, or tobacco.

• Ethanol

Other Medical Problems

The presence of other medical problems may affect the use of this medicine. Make sure you tell your doctor if you have any other medical problems, especially:

• Anemia, megaloblastic (caused by not enough folic acid)—Should not be used in patients with this condition.

• Asthma or
• Folate deficiency (vitamin B9) or
• Glucose-6-phosphate dehydrogenase (G6PD) deficiency or
• HIV or AIDS or
• Kidney disease or
• Liver disease or
• Seizures, history of—Use with caution. May have an increased chance of side effects.

Related/similar drugs

prednisone, amoxicillin, doxycycline, azithromycin, cephalexin, ciprofloxacin, metronidazole

Proper use of sulfamethoxazole/trimethoprim

A nurse or other trained health professional will give you this medicine. This medicine is given through a needle placed in one of your veins.

Precautions while using sulfamethoxazole/trimethoprim

It is very important that your doctor check your progress at regular visits to make sure that this medicine is working properly. Blood tests may be needed to check for unwanted effects.

Using this medicine while you are pregnant can harm your unborn baby. Use an effective form of birth control to keep from getting pregnant. If you think you have become pregnant while using the medicine, tell your doctor right away. Do not breastfeed while using the medicine.

Very rarely, this medicine has caused severe side effects. If you start to have a skin rash, or if you think you are having a severe skin reaction, call your doctor or nurse right away. Symptoms of a severe reaction may include a skin rash, skin color that is very pale or yellow, or skin with purple spots, along with a sore throat, fever, muscle pain, cough, and trouble with breathing.

Check with your doctor right away if you have abdominal or stomach cramps; bloating; watery and severe diarrhea, which may also be bloody; nausea or vomiting; or unusual tiredness or weakness. These may be symptoms of a serious intestinal infection.

This medicine may cause serious allergic reactions, including anaphylaxis. Anaphylaxis can be life-threatening and requires immediate medical attention. Check with your doctor right away if you have a rash; itching; swelling of the face, tongue, and throat; trouble with breathing; shortness of breath; or chest pain after you get the injection.

Before you have any medical tests, tell the medical doctor in charge that you are taking this medicine. The results of some tests may be affected by this medicine.

Side Effects of sulfamethoxazole/trimethoprim

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 or nurse immediately if any of the following side effects occur:

Rare

• Abdominal or stomach pain
• black, tarry stools
• blistering, peeling, or loosening of skin
• changes in skin color
• chest pain
• chills
• cough or hoarseness
• dark urine
• diarrhea
• dizziness
• fever with or without chills
• general feeling of tiredness or weakness
• headache
• itching
• joint or muscle pain
• light-colored stools
• loss of appetite
• lower back or side pain
• nausea
• pain, tenderness, or swelling of foot or leg
• painful or difficult urination
• pale skin
• rash
• red irritated eyes
• red skin lesions, often with a purple center
• shortness of breath
• sore throat
• sores, ulcers, or white spots in mouth or on lips
• swollen or painful glands
• tightness in chest
• unpleasant breath odor
• unusual bleeding or bruising
• unusual tiredness or weakness
• vomiting of blood
• wheezing
• yellow eyes or skin

Incidence not known

• Abdominal tenderness
• back, leg, or stomach pains
• bleeding gums
• bleeding under the skin
• blindness or vision changes
• blisters, hives, or itching
• bloating
• blood in urine or stools
• bluish-colored lips, fingernails, or palms
• burning, crawling, itching, numbness, painful, prickling, "pins and needles", or tingling feelings
• burning of face or mouth
• clumsiness or unsteadiness
• cloudy urine
• confusion
• constipation
• continuing ringing or buzzing or other unexplained noise in ears
• convulsions
• cracks in the skin
• decreased frequency or amount of urine
• diarrhea, watery and severe, which may also be bloody
• difficulty breathing
• difficulty swallowing
• dizziness or lightheadedness
• fainting spells
• general body swelling
• general feeling of discomfort or illness
• hair loss
• hearing loss
• increased blood pressure
• increased thirst
• indigestion
• irregular heartbeat
• large, flat, blue or purplish patches in the skin
• large, hive-like swelling on face, eyelids, lips, tongue, throat, hands, legs, feet, or sex organs
• loss of heat from the body
• muscle or joint pain
• nosebleeds
• not able to pass urine
• numbness or tingling in hands, feet, or lips
• pain or burning while urinating
• pains in the stomach, side, or abdomen, possibly radiating to the back
• painful knees and ankles
• pinpoint red spots on skin
• puffiness or swelling of the eyelids or around the eyes, face, lips or tongue
• raised red swellings on the skin, the buttocks, legs or ankles
• rapid heart rate
• red, swollen skin
• redness of the white part of the eyes
• redness, swelling, or soreness of tongue
• scaly skin
• shakiness and unsteady walk
• soreness of muscles
• stiff neck or back
• swelling of face, hands, legs, and feet
• swelling or inflammation of the mouth
• trouble breathing
• unsteadiness, trembling, or other problems with muscle control or coordination
• unusual weight loss
• weakness in hands or feet
• weakness or heaviness of legs
• weight gain

Some 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. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

• Hives or welts
• passing of gas
• redness of skin
• stomach pain, fullness, or discomfort

Incidence not known

• Discouragement
• feeling of constant movement of self or surroundings
• feeling sad or empty
• increased sensitivity of skin to sunlight
• irritability
• lack of feeling or emotion
• loss of interest or pleasure
• nervousness
• redness or other discoloration of skin
• seeing, hearing, or feeling things that are not there
• sensation of spinning
• severe sunburn
• sleeplessness
• trouble concentrating
• trouble sleeping
• unable to sleep
• uncaring

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

Available Dosage Forms:

• Solution

Therapeutic Class: Sulfonamide Combination

Pharmacologic Class: Folic Acid Antagonist

Chemical Class: Sulfonamide

Frequently asked questions

• What drugs should be avoided with a sulfa allergy?
• Does Bactrim cause headaches?
• Can I drink alcohol when taking sulfamethoxazole / trimethoprim DS?
• What dose of co-trimoxazole is used in a patient with a UTI?

View more FAQ

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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