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trimethoprim - sulfamethoxazole

By Quad Pharmaceuticals

What is this medication for?

Trimethoprim and sulfamethoxazole both belong to the class of medications called antibiotics. This combination of antibiotics is used to treat infections caused by certain bacteria. It is most commonly used to treat infections of the bladder, ear, intestine, and lung. It works by killing the bacteria that cause these infections.

Your doctor may have suggested this medication for conditions other than those listed here. As well, some forms of this medication may not be used for all of the conditions discussed here. If you are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

What form(s) does this medication come in?

Sulfamethoprim® is no longer being manufactured for sale in the USA.

Some medications may have other generic brands available. Always ask your doctor or pharmacist about the safety of switching between brands of the same medication.

How should I use this medication?

The usual recommended dose of trimethoprim - sulfamethoxazole for adults and children over 12 years of age is 2 regular-strength tablets, 1 double-strength tablet, or 4 teaspoonfuls (20 mL) taken twice a day in the morning and evening for 10 to 14 days, with or without food. Taking the medication with food will reduce the risk of stomach upset.

One single-strength tablet contains 80 mg trimethoprim and 400 mg sulfamethoxazole, while one double-strength tablet contains 160 mg trimethoprim and 800 mg sulfamethoxazole. Children's doses vary according to body weight and are usually given in the liquid form.

Take this medication with a full 8-ounce glass of water. Drink several additional glasses of water every day, unless otherwise instructed by your doctor.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important that this medication be taken exactly as prescribed by your doctor. Finish all this medication, even if you have started to feel better. Skipping doses or not completing the full course of therapy may (1) decrease the effectiveness of the immediate treatment and (2) increase the likelihood that bacteria will develop resistance and will not be treatable by trimethoprim tablets or other antibacterial drugs in the future.

If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Who should NOT take this medication?

Trimethoprim - sulfamethoxazole should not be used by or given to anyone who:

  • is allergic to trimethoprim, sulfamethoxazole, other sulfonamide-containing medications (sulfa drugs), or any ingredients of the medication
  • is breast-feeding
  • is pregnant
  • is younger than 2 months of age
  • has a history of a drug-induced blood disorder called immune thrombocytopenia
  • has certain types of blood disorders
  • has severe liver damage
  • has severe kidney problems (when kidney function cannot be monitored)
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Reviewer: Marlene Krempasky
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