What is Septrin® (sulfamethoxazole/ trimethoprim) used for?

Septrin® is commonly used for the treatment of the following infections when owing to sensitive organisms, such as:

  • Pneumocystis jiroveci (P. carinii)
  • Toxoplasmosis
  • Nocardiosis

The following infections may be treated with Septrin® where there is bacterial evidence of sensitivity to Septrin® and good reason to prefer the combination of antibiotics in Septrin® to a single antibiotic:

  • Acute uncomplicated urinary tract infection
  • Acute otitis media
  • Acute exacerbation of chronic bronchitis

How should I take Septrin® (sulfamethoxazole/ trimethoprim)?

Septrin® is taken by mouth. It may be preferable to take Septrin® with some food or drink to minimize the possibility of gastrointestinal disturbances.

How do I store Septrin® (sulfamethoxazole/ trimethoprim)?

Septrin®  is best stored at room temperature away from direct light and moisture. To prevent drug damage, you should not store Septrin® in the bathroom or the freezer. There may be different brands of Septrin® that may have different storage needs. It is important to always check the product package for instructions on storage, or ask your pharmacist. For safety, you should keep all medicines away from children and pets.

You should not flush Septrin® down the toilet or pour them into a drain unless instructed to do so. It is important to properly discard this product when it is expired or no longer needed. Consult your pharmacist for more details about how to safely discard your product.

Precautions & warnings

What should I know before using Septrin® (sulfamethoxazole/ trimethoprim)?

Septrin® should not be given to patients with a history of hypersensitivity to sulphonamides, trimethoprim, co-trimoxazole or any excipients of Septrin®.

Contraindicated in patients showing marked liver parenchymal damage.

Contraindicated in severe renal insufficiency where repeated measurements of the plasma concentration cannot be performed.

Septrin® should not be given to premature babies nor to full-term infants during the first 6 weeks of life except for the treatment /prophylaxis of PCP in infants 4 weeks of age or greater.

Is it safe during pregnancy or breastfeeding?

There are no adequate studies in women for determining risk when using this medication during pregnancy or while breastfeeding. Please always consult with your doctor to weigh the potential benefits and risks before taking this medication. This medication is pregnancy risk category D, according to the US Food and Drug Administration (FDA).

FDA pregnancy risk category reference below:

  • A=No risk
  • B=No risk in some studies
  • C=There may be some risk
  • D=Positive evidence of risk
  • X=Contraindicated
  • N=Unknown

Side effects

What side effects can occur from Septrin® (sulfamethoxazole/ trimethoprim)?

Like all medicines, Septrin® can cause side effects. You may experience the following side effects.

These allergic reactions are:

  • Breathing problem
  • Fainting
  • Swelling of face
  • Swelling of mouth, tongue or throat
  • Chest pain
  • Red patches on the skin

Very common (more than 1 in 10 people)

  • High levels of potassium in your blood, which can cause abnormal heart beats (palpitations).

Common (less than 1 in 10 people)

  • An infection called thru
  • Headache
  • Feeling sick (nause)
  • Diarrhea
  • Skin rashes

Not everyone experiences these side effects. There may be some side effects not listed above. If you have any concerns about a side-effect, please consult your doctor or pharmacist.


What drugs may interact with Septrin® (sulfamethoxazole/ trimethoprim)?

Septrin® may interact with other drugs that you are currently taking, which can change how your drug works or increase your risk for serious side effects. To avoid any potential drug interactions, you should keep a list of all the drugs you are using (including prescription drugs, nonprescription drugs and herbal products) and share it with your doctor and pharmacist. For your safety, do not start, stop, or change the dosage of any drugs without your doctor’s approval.

Products may interact with this drug, including:

Does food or alcohol interact with Septrin® (sulfamethoxazole/ trimethoprim)?

Septrin® may interact with food or alcohol by altering the way the drug works or increase the risk for serious side effects. Please discuss with your doctor or pharmacist any potential food or alcohol interactions before using this drug.

What health conditions may interact with Septrin® (sulfamethoxazole/ trimethoprim)?

Septrin® may interact with your health condition. This interaction may worsen your health condition or alter the way the drug works. It is important to always let your doctor and pharmacist know all the health conditions you currently have.


The information provided is not a substitute for any medical advice. You should ALWAYS consult with your doctor or pharmacist before using Septrin® (sulfamethoxazole/ trimethoprim).

What is the dose of Septrin® (sulfamethoxazole/ trimethoprim) for an adult?

Adults and children over 12 years:

The recommended dose is two tablets every 12 hours.

This dosage approximates to 6 mg trimethoprim and 30 mg sulfamethoxazole per kilogram body weight per 24 hours.

What is the dose of Septrin® (sulfamethoxazole/ trimethoprim) for a child?

The following dose schedules may be used for the duration of the period at risk (Prevention):

  • Standard dosage is taken in two divided doses, seven days per week.
  • Standard dosage is taken in two divided doses, three times per week on alternate days.
  • Standard dosage is taken in two divided doses, three times per week on consecutive days.
  • Standard dosage is taken as a single dose, three times per week on consecutive days.

The daily dose given on a treatment day approximates to 150 mg trimethoprim/m2/day and 750 mg sulfamethoxazole/m2/day. The total daily dose should not exceed 320 mg trimethoprim and 1600 mg sulfamethoxazole.

How is Septrin® (sulfamethoxazole/ trimethoprim) available?

Septrin® is available in the following dosage forms and strengths:

  • Septrin® 80 mg/400 mg Tablets

What should I do in case of an emergency or overdose?

In case of an emergency or an overdose, call your local emergency services or go to your nearest emergency room.

What should I do if I miss a dose?

If you miss a dose of Septrin®, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and take your regular dose as scheduled. Do not take a double dose.

Hello Health Group does not provide medical advice, diagnosis or treatment.

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Review Date: January 24, 2017 | Last Modified: December 19, 2019

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