Treatment for bacterial infections involves the use of antibiotics and combination antibiotics. A common, and powerful combination antibiotic is Sulfamethoxazole/Trimethoprim (SMX/TMP), also known as Co-trimoxazole, prescribed for treating different types of bacterial infections. Patients diagnosed with gonorrhea and chlamydia often assume that all antibiotics would be effective against the condition. Following sub-sections offer a detailed look at this antibiotic and also offer complete clarity through answers to the question – is sulfamethoxazole/TMP effective against gonorrhea and chlamydia? This will help individuals avoid intake of wrong medications.

What is SMX/TMP used for treating?

Sulfamethoxazole/TMP (SMX/TMP) is used for treating different bacterial infections, specifically the following.

  • Urinary tract infections: SMX/TMP is used to treat uncomplicated urinary tract infections caused by susceptible bacteria.
  • Respiratory tract infections: SMX/TMP is also used to treat respiratory tract infections, including bronchitis and pneumonia.
  • Gastrointestinal infections: The antibiotic is used to treat gastrointestinal infections like traveler’s diarrhea.
  • Skin and soft tissue infections: The combination antibiotic is also effective in treating skin and soft tissue infections.
  • Pneumocystis jirovecii pneumonia: The Co-trimoxazole is used in the treatment and prevention of Pneumocystis jirovecii pneumonia, a serious fungal infection in individuals with weakened immune systems.

SMX/TMP is effective in treating bacterial infections and will not work against viral infections including colds and flu.

What are the different forms of sulfamethoxazole/TMP and how should it be used?

Sulfamethoxazole/Trimethoprim (SMX/TMP) is available in different forms, including tablets, oral suspension, and injection. The actual dosage and duration of treatment depends on the type and severity of the infection, as well as the patient’s age, weight, and medical history. The dose is usually divided into two or more daily doses.

For adults, the typical dose of SMX/TMP for the treatment of bacterial infections is one double-strength tablet or one single-strength tablet twice daily. The duration of treatment could be a few days to few weeks, depending on the infection. For children, the dosage of SMX/TMP is based on weight and is usually in the form of an oral suspension. In certain instances, SMX/TMP may be administered as an injection, in a vein or muscle, with the dosage and frequency depending on the infection.

What is gonorrhea and chlamydia?

Gonorrhea and chlamydia are two (STIs) sexually transmitted infections, that are attributed to bacteria. Gonorrhea is caused by the bacteria Neisseria gonorrhoeae and is known to infect the genital tract, rectum, and throat. The infection spreads through unprotected sexual contact from an infected person and common symptoms include painful urination, discharge from the penis/vagina, and pain/swelling in the testicles. In rare instances, gonorrhea may not present any symptoms, and when left untreated, the condition can result in serious complications. This includes possible pelvic inflammatory disease, infertility, and elevated risk of exposure to HIV transmission.

Chlamydia is caused by the bacteria Chlamydia trachomatis and is known to infect the genital tract, rectum, and throat. This infection is also spreads through unprotected sexual contact and can result in similar symptoms. Similar to gonorrhea, when left untreated chlamydia can result in serious complications.  Both gonorrhea and chlamydia can be treated with antibiotics, after a detailed diagnosis.

What are the treatment options for gonorrhea and chlamydia?

Treatment options for gonorrhea and chlamydia are similar, with antibiotics. However, there could be variations in antibiotics and treatment regimen, depending on the severity of the infection, the patient’s medical history, and other factors. Gonorrhea can be treated with a single injection of ceftriaxone, along with an oral antibiotic like azithromycin. When the infection is known to be resistant to these antibiotics, other antibiotics may be used. Chlamydia can be treated with a course of oral antibiotics like azithromycin or doxycycline, and the course is typically several days or a week. Patients are also to abstain from sexual activity during treatment and may need to undergo re-testing after treatment to ensure that the infection has been fully cured.

In both the conditions, it is necessary to complete the full course of antibiotics, even if symptoms improve before the completion of course.

What is the mechanism of action of sulfamethoxazole/TMP

Sulfamethoxazole/Trimethoprim (SMX/TMP works by targeting different steps in the bacterial metabolic pathway, preventing the bacteria from growing and reproducing. Sulfamethoxazole is a sulfonamide antibiotic that inhibits the production of folic acid, a vitamin essential for the synthesis of DNA, RNA, and proteins in bacteria. Sulfamethoxazole blocks the activity dihydropteroate synthase, an enzyme, necessary for the production of folic acid in bacteria, and this prevents the bacteria from synthesizing the building blocks of DNA and RNA. This in turn impacts the ability of the bacterial cell to grow and reproduce.

Trimethoprim is a diaminopyrimidine antibiotic that inhibits the bacterial enzyme dihydrofolate reductase, involved in the synthesis of folic acid. By inhibiting this enzyme, trimethoprim blocks the production of folic acid at a later stage in the metabolic pathway. This has the effect of disrupting the ability of the bacterial cell to produce the necessary building blocks for DNA and RNA synthesis.

As a combination, sulfamethoxazole and trimethoprim inhibit different steps in the folic acid synthesis pathway, preventing bacterial growth and reproduction.

Is sulfamethoxazole/TMP effective against gonorrhea and chlamydia?

Sulfamethoxazole/Trimethoprim is not considered as an effective treatment option for gonorrhea or chlamydia. This is mainly because the conditions are attributed to bacteria that are different from the ones that are targeted by SMX/TMP.


As mentioned earlier, gonorrhea and chlamydia are treated with antibiotics, and the effective ones for the conditions include azithromycin, doxycycline, or ceftriaxone. This depends on the specific infection and the patient’s medical history. This category of antibiotics is known to be effective against the specific bacteria strains that cause these infections.

SMX/TMP is effective in treating other bacterial infections, listed out earlier. However, the use of the combination antibiotic is to be only as per the recommendations of a specialist. Overuse or inappropriate use of antibiotics may end up causing antibiotic resistance, and this could affect the ability to heal or be treated effectively when infected in the future. 



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