Precautions and Warnings With Sulfamethoxazole/Trimethoprim

Specific Warnings and Precautions

Some warnings and precautions to be aware of with sulfamethoxazole/trimethoprim include the following:
  • Although it is generally a relatively safe antibiotic for most people, rarely, sulfamethoxazole/trimethoprim has caused deaths due to various problems.
  • Sulfamethoxazole/trimethoprim contains a sulfonamide (a "sulfa" drug). Do not take this medication if you have a sulfa allergy.
  • Let your healthcare provider know if you develop an unexplained sore throat, fever, joint pain, pale skin, bruising, yellow skin (jaundice), coughing, or shortness of breath while taking sulfamethoxazole/trimethoprim. These may be signs of serious reactions to the drug.
  • Stop taking sulfamethoxazole/trimethoprim and contact your healthcare provider immediately if you develop a skin rash while taking it. While it may just be a simple rash, it could turn out to be a life-threatening reaction, such as Stevens-Johnson syndrome or toxic epidermal necrolysis.
  • Let your healthcare provider know if you experience bloody or watery diarrhea. While diarrhea is a common side effect of antibiotics, bloody or watery diarrhea may be a sign of a serious reaction to sulfamethoxazole/trimethoprim that can occur when certain bacteria (Clostridium difficile) overgrow in the colon. This severe reaction can occur long after you stop taking sulfamethoxazole/trimethoprim and can be life-threatening.
  • Check with your healthcare provider before taking sulfamethoxazole/trimethoprim if you have glucose-6-phosphate dehydrogenase deficiency or severe asthma, as serious side effects could occur.
  • Sulfamethoxazole/trimethoprim may worsen certain thyroid disorders (especially hypothyroidism) or porphyria. If you have either of these problems, check with your healthcare provider before taking this drug.
  • Sulfamethoxazole/trimethoprim should not be used to treat infections caused by β-hemolytic streptococcal bacteria, as it is not effective for completely getting rid of this type of bacteria (which might increase the risk of developing rheumatic fever due to the infection).
  • Overuse of antibiotics (including sulfamethoxazole/trimethoprim) increases the risk for developing antibiotic-resistant bacteria. Your healthcare provider should prescribe antibiotics only when necessary (and only to treat bacterial infections). Antibiotics are not effective for treating viral infections, such as the common cold or the flu.
  • Make sure your healthcare provider knows if you have kidney or liver disease, as you may need a lower dosage of this medication (or the medication may not even be recommended, in severe cases).
  • There have been reports of low blood sugar (hypoglycemia) possibly due to sulfamethoxazole/trimethoprim. While most common in people with diabetes, it has also been reported in non-diabetic individuals.
  • Although sulfamethoxazole/trimethoprim is approved to treat and prevent Pneumocystis carinii pneumonia in people with HIV or AIDS, it should be noted that people with HIV or AIDS have a higher risk of sulfamethoxazole/trimethoprim side effects. Your healthcare provider should carefully monitor you for side effects.
  • It is very important to take sulfamethoxazole/trimethoprim exactly as prescribed. Skipping doses or stopping it too early (even if you feel better) can lead to bacterial resistance to the drug.
  • Sulfamethoxazole/trimethoprim can interact with many other medications (see Drug Interactions With Sulfamethoxazole/Trimethoprim).
  • Sulfamethoxazole/trimethoprim can cause electrolyte problems, such as high potassium or low sodium levels in the blood. If you already have electrolyte problems or if you have kidney problems, your electrolytes should be monitored using blood tests while taking this medication.
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Sulfamethoxazole Trimethoprim Information

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