- 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:
- Your Child Is Sick. Do You Call Your Doctor or Head to the ER?
- Mental Health Care Shortage Could Play Role in U.S. Youth Suicides
- Shopping Black Friday for TVs, Furniture? Don't Forget the Tip-Over Kit
- Keeping Thanksgiving Day Kitchens Safe for the Whole Family
- All the Flavor, Better Health: Holiday Dinner Ingredient Swaps That Work
- More Health News »
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.
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
Diarrhea is a change in the frequency and looseness of bowel movements. Symptoms associated with diarrhea are cramping, abdominal pain, and the sensation of rectal urgency. Causes of diarrhea include viral, bacterial, or parasite infection, gastroenteritis, food poisoning, and drugs. Absorbents and anti-motility medications are used to treat diarrhea.
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 lives in the bowel and near the anus, causes most UTIs. UTI symptoms include pain, abdominal pain, mild fever, urinary urgency, and frequency. Treatment involves a course of antibiotics.
Middle Ear Infection (Otitis Media)
A middle ear infection (otitis media) can cause earache, temporary hearing loss, and pus drainage from the ear. It is most common in babies, toddlers, and young children. Learn about causes and treatment.
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 deficits, certain medications, anemia, blood loss, fasting, and loss of electrolytes and minerals associated with surgery can also produce fatigue. Exercise, physical exertion, aging, and the overall health status of patients are additional factors that play a role in making people feel tired after surgery.
Impetigo is a contagious skin infection caused by staph and strep bacteria. There are two types of impetigo: nonbullous and bullous. Symptoms of nonbullous impetigo include small blisters on the nose, face, arms, or legs and possibly swollen glands. Bullous impetigo signs include blisters in various areas, particularly in the buttocks area. Treatment involves gentle cleansing, removing the crusts of popped blisters, and the application of prescription-strength mupirocin antibiotic ointment.
Kidney Infection (Pyelonephritis)
Kidney infection (pyelonephritis) usually is caused by E. coli and other bacteria that have spread from the bladder from a UTI (urinary tract infection), poor hygiene, sexual intercourse, pregnancy, catheter, cystoscope exam, surgery, kidney stones, or prostate enlargement. Symptoms of kidney infection include back pain, frequent urination, pain during urination, fever, and or pus or blood in the urine. Kidney infection can be cured with antibiotic treatment. Cranberry juice may prevent UTIs, but that hasn’t been proven in all research studies.
MRSA (methicillin-resistant Staphylococcus aureus) bacteria causes skin infections with the following signs and symptoms: cellulitis, abscesses, carbuncles, impetigo, styes, and boils. Normal skin tissue doesn't usually allow MRSA infection to develop. Individuals with depressed immune systems and people with cuts, abrasions, or chronic skin disease are more susceptible to MRSA infection.
SIBO (Small Intestinal Bacterial Overgrowth)
Small intestinal bacterial overgrowth (SIBO) refers to a condition in which abnormally large numbers of bacteria (at least 100,000 bacteria per ml of fluid) are present in the small intestine, but they are more like the bacteria that are found in the colon. There are many conditions associated with SIBO, including: Diabetes Scleroderma Crohn's disease Irritable bowel syndrome (IBS) It has been theorized that SIBO may be responsible for the symptoms of at least some patients with irritable bowel syndrome. Symptoms of SIBO include: Excess gas Abdominal bloating Abdominal pain Treatment for SIBO can include: Antibiotics Probiotics Low FODMAP Diet
Prostatitis (Inflammation of the Prostate Gland)
Prostatitis is an inflammation of the prostate gland. Signs and symptoms of prostatitis include painful or difficulty urinating; fever; chills; body aches; blood in the urine; pain in the rectum, groin, abdomen, or low back; and painful ejaculation or sexual dysfunction. Causes of prostatitis include STDs, bacteria from urinary tract infections, or E. coli. Treatment for prostatitis depends on if it is a bacterial infection or chronic inflammation of the prostate gland.
Cystic acne is distinguished by painful nodules on the chest, face, neck, and back. This form of acne is known to scar. Treatment may incorporate the use of hormonal therapies, oral antibiotics, and prescription medications.
Whooping Cough (Pertussis)
Whooping cough (pertussis) is a highly contagious respiratory infection caused by the bacteria Bordetella pertussis. There are an estimated 300,000 plus deaths annually from whooping cough (pertussis). Whooping cough commonly affects infants and young children but can be prevented with immunization with the vaccine. First stage whooping cough symptoms are a runny nose, sneezing, low-grade fever, a mild cough with the cough gradually becoming more severe. After one to two weeks, the second stage of whooping cough begins.
Typhoid fever is an illness caused by the Salmonella typhi bacteria. The illness is contracted by ingesting the bacteria in contaminated water or food. Symptoms include headaches, fever, diarrhea, lethargy, aches and pains, and poor appetite. Treatment focuses on killing the Salmonella bacteria with antibiotics.
Travelers' diarrhea is generally contracted by eating contaminated food or drinking contaminated water. Food is the primary source of travelers' diarrhea. Enterotoxigenic E. coli is the cause of up to 70% of all cases of travelers' diarrhea. There are five unique classes of E. coli that causes gastroenteritis. Other bacteria responsible for travelers' diarrhea include Campylobacter, jejuni, shigella, and salmonella. Viruses such as rotavirus and Norwalk virus (norovirus) and giardia lamblia a parasite may cause travelers' diarrhea. Prevention is careful eating and drinking of water.
Listeria is a type of bacteria that can cause food poisoning. Listeriosis symptoms include diarrhea, nausea, and fever. Pregnant women are 20 times more likely than other healthy adults to get listeriosis. Listeria infection is treated with antibiotics.
Mycobacterium marinum (M. marinum) is bacteria found in fresh and saltwater that can infect the skin through cuts or scrapes, causing granulomas to appear on the skin near the site of infection. This infection may be treated with a long course of oral antibiotics.
AIDS (Acquired Immunodeficiency Syndrome)
AIDS is the advanced stage of HIV infection. Symptoms and signs of AIDS include pneumonia due to Pneumocystis jiroveci, tuberculosis, toxoplasmosis, seizures, weakness, meningitis, yeast infection of the esophagus, and Kaposi's sarcoma. Anti-retroviral therapy (HAART) is used in the treatment of AIDS.
Human Immunodeficiency Virus (HIV)
HIV (human immunodeficiency virus) infection left untreated causes AIDS (acquired immunodeficiency syndrome). The human immunodeficiency virus (HIV) is a type of virus called a retrovirus, which can infect humans when it comes in contact with tissues that line the vagina, anal area, mouth, or eyes, or through a break in the skin. HIV infection is generally a slowly progressive disease in which the virus is present throughout the body at all stages of the disease. Three stages of HIV infection have been described. The initial stage of infection (primary infection), which occurs within weeks of acquiring the virus, often is characterized by the flu- or mono-like illness that generally resolves within weeks. The stage of chronic asymptomatic infection (meaning a long duration of infection without symptoms) lasts an average of eight to 10 years without treatment. The stage of symptomatic infection, in which the body's immune (or defense) system has been suppressed and complications have developed, is called the acquired immunodeficiency syndrome (AIDS). The symptoms are caused by the complications of AIDS, which include one or more unusual infections or cancers, severe loss of weight, and intellectual deterioration (called dementia). When HIV grows (that is, by reproducing itself), it acquires the ability to change (mutate) its own structure. These mutations enable the virus to become resistant to previously effective drug therapy. The goals of drug therapy are to prevent damage to the immune system by the HIV virus and to halt or delay the progress of the infection to symptomatic disease. Therapy for HIV includes combinations of drugs that decrease the growth of the virus to such an extent that the treatment prevents or markedly delays the development of viral resistance to the drugs. The best combination of drugs for HIV are those that effectively suppress viral replication in the blood and also are well tolerated and simple to take so that people can take the medications consistently without missing doses.
The bacteria Brucella causes brucellosis, an infectious zoonotic disease in humans. Symptoms and signs include fatigue, fever, sweating, and appetite loss. The preferred treatment is doxycycline and rifampin taken for six to eight weeks.
Toxoplasmosis (toxo) is a parasitic infection that causes flu-like symptoms, swollen lymph nodes, and muscle aches and pains that may last from a few days to several weeks. Toxoplasmosis can be contracted by touching the hands to the mouth after gardening, cleaning a cat's litter box, or anything that came into contact with cat feces. Toxoplasmosis can also be contracted by eating raw or partly cooked meat, especially pork or lamb, or touching the hands to the mouth after contact with raw or undercooked meat
Enterovirulent E. coli (EEC)
Enterovirulent Escherichia coli (E. coli) are strains of related bacteria that have a strong propensity to cause gastrointestinal tract infections. Examples of strains include: EHEC (enterohemorrhagic E. coli), ETEC (enterotoxigenic E. coli), EPEC (enteropathogenic E. coli), EIEC (enteroinvasive E. coli), EAEC (enteroadherent E. coli), and EAggEC (enteroaggregative E. coli). Symptoms may vary depending on the strain the individual contracts. Infection is spread generally through contaminated food or drink.
Granulomatosis With Polyangiitis
Granulomatosis with polyangiitis is a condition that usually affects young or middle-aged adults, is an inflammation of the arteries supplying blood to the sinuses, lungs, and kidneys. Symptoms of granulomatosis with polyangiitis include bloody sputum, fatigue, weight loss, joint pain, sinusitis, shortness of breath, and fever. Granulomatosis with polyangiitis may be fatal within months without treatment. Treatment aims to stop inflammation with high doses of prednisone and cyclophosphamide.
Melioidosis (Whitmore's disease) is an infectious disease caused by Burkholderia pseudomallei bacteria. Symptoms include bronchitis, pneumonia, fever, headache, loss of appetite, cough, and chest pain. Treatment involves antibiotics or surgical removal of the lung abscess in severe cases.
Q fever is a highly infectious disease that causes high fever, diarrhea, cough, and sweating. Infected animals may transmit Q fever to humans. Antibiotics are available to treat Q fever.
Cyclospora Infection (Cyclosporiasis)
Cyclospora cayetanensis is a parasite that causes infection when humans ingest food contaminated with feces from an infected individual. Symptoms include profuse diarrhea, abdominal pain, gas, cramping, and fatigue. A 7-day course of Bactrim or Septra is the standard treatment for cyclosporiasis.
Treatment & Diagnosis
- Leg Sores
- Bladder Infection
- Cloudy Urine
- Groin Pain
- Urine Odor
- Urinary Tract Infection (UTI)
- Urinary Urgency
- Kidney Infection (Pyelonephritis)
- MRSA Infection
- Typhoid Fever
- Doctor: Checklist to Take To Your Doctor's Appointment
- Small Intestinal Bacterial Overgrowth (SIBO)
- Polycystic Kidney Disease (PKD)
- Whooping Cough (Pertussis)
- Granulomatosis With Polyangiitis (GPA)
- MRSA FAQs
- Drugs: Buying Prescription Drugs Online Safely
- 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: The Most Common Medication Errors
- Medication Disposal
- Dangers of Mixing Medications
- 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