- HIV AIDS Myths and Facts Slideshow Pictures
- Take the HIV/AIDS Quiz
- AIDS Retrospective Slideshow Pictures
- What is sulfamethoxazole and trimethoprim, and how does it work (mechanism of action)?
- What brand names are available for sulfamethoxazole and trimethoprim?
- Is sulfamethoxazole and trimethoprim available as a generic drug?
- Do I need a prescription for sulfamethoxazole and trimethoprim?
- What are the uses for sulfamethoxazole and trimethoprim?
- What are the side effects of sulfamethoxazole and trimethoprim?
- What is the dosage for sulfamethoxazole and trimethoprim?
- Which drugs or supplements interact with sulfamethoxazole and trimethoprim?
- Is sulfamethoxazole and trimethoprim safe to take if I'm pregnant or breastfeeding?
- What else should I know about sulfamethoxazole and trimethoprim?
What is sulfamethoxazole and trimethoprim, and how does it work (mechanism of action)?
Bactrim is a combination of two synthetic (man-made) antibiotics, sulfamethoxazole and trimethoprim. Both drugs reduce the ability of some bacteria to utilize folic acid for growing. Sulfamethoxazole is an anti-bacterial sulfonamide, a "sulfa" drug. It disrupts the production of dihydrofolic acid while trimethoprim disrupts the production of tetrahydrofolic acid. Dihydrofolic acid and tetrahydrofolic acid are forms of folic acid that bacteria and human cells use for producing proteins. Trimethoprim inhibits production of tetrahydrofolic acid by inhibiting the enzyme responsible for making tetrahydrofolic acid from dihydrofolic acid. By combining both drugs, two important steps required in the production of bacterial proteins are interrupted, and the combination is more effective than either drug alone. Bactrim was approved by the FDA in 1973.
What brand names are available for sulfamethoxazole and trimethoprim?
Bactrim, Bactrim DS, Sulfatrim Pediatric
What are the uses for sulfamethoxazole and trimethoprim?
Sulfamethoxazole/trimethoprim is used for treating infections due to susceptible bacteria. Examples include urinary tract infections, flares of chromic bronchitis due to bacteria, middle ear infections, for prevention of infections due to pneumococcus in organ transplant recipients, for the treatment or prevention of Pneumocystis carinii pneumonia, chancroid, and prevention of toxoplasma encephalitis in patients with AIDS.
What are the side effects of sulfamethoxazole and trimethoprim?
Common side effects of sulfamethoxazole/trimethoprim are:
Other side effects include:
What is the dosage for sulfamethoxazole and trimethoprim?
The recommended adult dose for urinary tract infections is one double strength tablet (Bactrim DS, Septra DS) or two single strength tablets every 12 hours for 10 to 14 days.
Flares of chronic bronchitis are treated with a similar regimen for 14 days.
Sulfamethoxazole/trimethoprim should be taken with 6 to 8 ounces of liquid to prevent crystals from forming in the urine. Persons with advanced kidney disease may require lower doses.
Which drugs or supplements interact with sulfamethoxazole and trimethoprim?
Sulfamethoxazole/trimethoprim can enhance the blood-thinning effects of warfarin (Coumadin), possibly leading to bleeding. Sulfonamides such as sulfamethoxazole can increase the metabolism (break-down and elimination) of cyclosporine (causing loss of effectiveness of cyclosporine), and can add to the kidney damage caused by cyclosporine.
Blood levels of phenytoin (Dilantin) may be increased by treatment with sulfamethoxazole/trimethoprim. This may lead to side effects associated with phenytoin (Dilantin, Dilantin-125) such as dizziness, and reduced attention.
Sulfamethoxazole/trimethoprim also may increase blood levels of digoxin (Lanoxin) and possibly lead to serious toxic effects. Anemia, due to a reduction in folic acid, can occur in persons receiving sulfamethoxazole/trimethoprim in combination with:
- valproic acid (Depakote, Depakote ER, Depakene, Depacon, Stavzor),
- methotrexate (Rheumatrex, Trexall),
- triamterene, or
Increased blood levels of potassium may occur when sulfamethoxazole/trimethoprim is combined with ACE inhibitors.
Is sulfamethoxazole and trimethoprim safe to take if I'm pregnant or breastfeeding?
Use of sulfonamides may cause bilirubin to be displaced from proteins in the infant's blood. Displacement of bilirubin can lead to jaundice and a dangerous condition called kernicterus in the infant. For this reason, sulfamethoxazole/trimethoprim should not be used near term (late in pregnancy) among women.
Sulfamethoxazole/trimethoprim should not be used by nursing mothers because sulfamethoxazole is excreted in milk and can cause kernicterus.
What else should I know about sulfamethoxazole and trimethoprim?
What preparations of sulfamethoxazole and trimethoprim are available?
Tablets: 160 mg trimethoprim and 800 mg sulfamethoxazole (Bactrim DS, Septra DS); 80 mg trimethoprim and 400 mg sulfamethoxazole (Bactrim; Septra).
How should I keep sulfamethoxazole and trimethoprim stored?
The tablets should be kept at room temperature, 15 C -30 C (59 F - 86 F).
Subscribe to MedicineNet's General Health Newsletter
Sulfamethoxazole and trimethoprim; cotrimoxazole (Bactrim, Bactrim DS, Septra, Septra DS) is a drug prescribed for urinary tract infections (UTIs), middle ear infections, respiratory infections, pneumonia, chancroid, for the prevention of infections of transplant recipients, and prevention of toxoplasma encephalitis in patients with AIDS. Side effects, dosage, drug interactions, pregnancy and breastfeeding safety information is also provided in the information.
Multimedia: Slideshows, Images & Quizzes
MRSA Quiz: Infection Symptoms & Treatment
It's the MRSA Quiz! For the carriers among us, you'd be surprised that the infectious superbug is lurking on this body part! Take...
Picture of Chancroid
A sexually transmitted infection (STI) caused by the bacterium Haemophilus ducreyi. See a picture of Chancroid and learn more...
Related Disease Conditions
Human Immunodeficiency Virus (HIV)
The human immunodeficiency virus (HIV) causes HIV infection and the acquired immunodeficiency syndrome (AIDS). Symptoms and signs...
Melioidosis (Whitmore's disease) is an infectious disease caused by Burkholderia pseudomallei bacteria. Symptoms include...
Prostatitis (Inflammation of the Prostate Gland)
Prostatitis is an inflammation of the prostate gland. Signs and symptoms of prostatitis include painful or difficulty urinating,...
Typhoid fever is an illness caused by the Salmonella typhi bacteria. The illness is contracted by ingesting the bacteria in...
Urinary Tract Infection (UTI)
A urinary tract infection (UTI) is an infection of the bladder, kidneys, ureters, or urethra. E. coli, a type of bacteria that...
Granulomatosis with Polyangiitis
Granulomatosis with polyangiitis is a condition that usually affects young or middle-aged adults, is an inflammation of the...
Diarrhea (Causes, Medicine, Remedies, Treatment)
Diarrhea is a change is the frequency and looseness of bowel movements. Symptoms associated with diarrhea are cramping, abdominal...
Mycobacterium marinum (M. marinum) is bacteria found in fresh and saltwater that can infect the skin through cuts or scrapes,...
Ear Infection (Otitis Media)
Middle ear infection or inflammation (otitis media) is inflammation of the middle ear. There are two forms of this type of ear...
Whooping Cough (Pertussis)
Whooping cough (pertussis) is highly contagious respiratory infection that is caused by the bacteria Bordetella pertussis. There...
Toxoplasmosis (toxo) is a parasitic infection that causes flu-like symptoms, swollen lymph nodes, and muscle aches and pains that...
Travelers' diarrhea is generally contracted by eating contaminated food or drinking contaminated water. Food is the primary...
Impetigo is a contagious skin infection caused by staph and strep bacteria. There are two types of impetigo: nonbullous and...
SIBO (Small Intestinal Bacterial Overgrowth)
Small intestinal bacterial overgrowth (SIBO) refers to a condition in which abnormally large numbers of bacteria (at least...
Kidney Infection (Pyelonephritis) Symptoms, Signs, Causes, Treatment
Kidney infection (pyelonephritis) usually is caused from bacteria that have spread from the bladder from a UTI (urinary tract...
MRSA (methicillin-resistant Staphylococcus aureus) bacteria causes skin infections with the following signs and symptoms:...
Shigellosis is a disease caused by the Shigella bacteria. Bloody diarrhea, stomach cramps, and fever are common symptoms. Mild...
The bacteria Brucella causes brucellosis, an infectious zoonotic disease in humans. Symptoms and signs include fatigue, fever,...
Acquired Immunodeficiency Syndrome
AIDS is the advanced stage of HIV infection. Symptoms and signs of AIDS include pneumonia due to Pneumocystis jiroveci,...
Enterovirulent E. coli (EEC)
Enterovirulent Escherichia coli (E. coli) are strains of related bacteria that have a strong propensity to cause gastrointestinal...
Listeria is a type of bacteria that can cause food poisoning. Listeriosis symptoms include diarrhea, nausea, and fever. Pregnant...
Cyclospora Infection (Cyclosporiasis)
Cyclospora cayetanensis is a parasite that causes infection when humans ingest food contaminated with feces from an infected...
Q fever is a highly infectious disease that causes high fever, diarrhea, cough, and sweating. Infected animals may transmit Q...
7 Reasons You Are Tired After Surgery
Postsurgical fatigue is normal and is due to a variety of factors. Depression, stress, and anxiety may produce fatigue. Sleep...
Cystic acne is distinguised by painful nodules on the chest, face, neck, and back. This formo of acne is known to scar. Treatment...
Treatment & Diagnosis
- Doctor: Checklist to Take To Your Doctor's Appointment
- Cloudy Urine
- Urine Odor
- Leg Sores
- Urinary Tract Infection (UTI)
- Bladder Infection
- MRSA Infection
- Kidney Infection (Pyelonephritis)
- Polycystic Kidney Disease (PKD)
- Urinary Urgency
- Groin Pain
- Whooping Cough (Pertussis)
- MRSA FAQs
- Medication Disposal
- Dangers of Mixing Medications
- How To Reduce Your Medication Costs
- Pharmacy Visit, How To Get The Most Out of Your Visit
- Indications for Drugs: Approved vs. Non-approved
- Drugs: Buying Prescription Drugs Online Safely
- Drugs: The Most Common Medication Errors
- Cyclospora Outbreak - Berry, Berry, Quite Contrary
- Generic Drugs, Are They as Good as Brand-Names?
Medications & Supplements
Prevention & Wellness
Health Solutions From Our Sponsors
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
FDA Prescribing Information