Sulfamethoxazole + trimethoprim - oral

Patient Medicine Information
Why do I need this medicine?
Sulfamethoxazole and Trimethoprim are combined in this medicine.

This medicine is an antibiotic. It is used to treat certain bacterial infections of the ears, lungs, and bladder.

Sulfamethoxazole + Trimethoprim may be used to treat other conditions as decided by your doctor.
How do I take this medicine?
Take Sulfamethoxazole + Trimethoprim exactly as directed by your doctor or according to the instructions on the label. Do not take more or less than instructed by your doctor.

You may take this medicine with food to reduce any stomach discomfort that it may cause. Try to take it at the same time each day.

Sulfamethoxazole + Trimethoprim is available as a tablet or as an oral suspension.

If you are taking an oral suspension, shake the bottle well before you take it to ensure that the liquid is evenly mixed. Use the measuring spoon or cup provided to measure your dose.

The dose of this medicine will be decided by your doctor. Your doctor will advise you on the treatment timeframe depending on the type and severity of your infection.

Take Sulfamethoxazole + Trimethoprim at regular intervals. Do not skip any doses. You must complete the entire course of this medicine. If you don't, the infection will not be properly controlled.
What should I do if I have forgotten to take this medicine?
Take the missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and return to your normal dosing schedule.

DO NOT double a dose under any circumstances.

If you often forget to take your medicine, let your doctor and pharmacist know.
When should I not use this medicine?
Do not take this medicine if you ever had an allergic reaction (e.g. rashes, breathlessness, swollen eyes) to sulfamethoxazole, trimethoprim or any other similar medicines such as sulfonamides.

Alert your doctor if you have the following conditions:
  • thrombocytopenia (lower than normal platelet counts in the blood)
  • megaloblastic anaemia (low red blood cell count in the body where the red blood cells are larger than normal)
  • porphyria (an inherited disorder that causes skin or nervous system abnormalities)
  • severe liver damage
  • severe kidney problems wherein a repeated measurement of blood concentrations cannot be performed
as this medicine may not be suitable for you.

Do not give Sulfamethoxazole + Trimethoprim to infants under 6 months old unless instructed to do so by the doctor.
What should I take note of while taking this medicine?
Inform your doctor if you have the following conditions:
  • severe allergy or asthma
  • thyroid problems
  • blood disorders
  • hyperkalaemia (high potassium levels in the blood)
  • malnutrition (nutrient imbalance due to an improper or insufficient diet)
  • taking medicines for epilepsy (fits or seizures)
  • G6PD deficiency (an inherited blood disorder that affects the red blood cell)
  • kidney disease
  • mild to moderate liver disease
Let your doctor know if you are pregnant or breastfeeding.

Be sure to check with your doctor or pharmacist before giving Sulfamethoxazole + Trimethoprim to a child or the elderly. Children and elderly people may be more sensitive to the side effects.

If you are going to have certain laboratory tests, inform your doctor that you are taking this medicine.

For as long as you are taking Sulfamethoxazole + Trimethoprim, you may need to have regular blood tests to check your body’s response to the medicine. Your doctor will advise you about how often you need to have blood tests.
What side effects could I experience?
Sulfamethoxazole + Trimethoprim may cause any of the following side effects: vomiting, loss of appetite, and drowsiness.

You may experience diarrhoea, nausea, stomach discomfort and headache while being treated with this medicine. These side effects are usually mild and will get better with rest. If you have diarrhoea, drink lots of water to replace the fluids lost. However, if you have severe diarrhoea or diarrhoea with severe stomach cramps or bloody stools, alert your doctor immediately.

Some side effects may need immediate medical help. Alert your doctor quickly if you experience any of the following:
  • rashes, breathlessness, swollen mouth or eyes
  • unusual bleeding or bruising, frequent and persistent sore throat with fever
  • yellowing of the skin or eyes, abdominal pain, dark coloured urine, tiredness
  • rashes with peeling of the skin or blistering of the lips, mouth or eyes accompanied by fever
Inform your doctor if any of these side effects do not go away or are severe, or if you experience other side effects.
Can I take this with other medicines?
Inform your doctor and pharmacist if you are taking any of these medicines:
  • medicines for diabetes e.g. glibenclamide, glipizide, repaglinide
  • medicines for HIV infection e.g. zidovudine, lamivudine
  • medicines for epilepsy (fits or seizures) e.g. phenytoin
  • warfarin (blood-thinning medicine)
  • rifampicin (medicine for TB, an infection known as tuberculosis)
  • methotrexate (medicine for cancer)
  • ciclosporin (medicine used in organ transplant or certain immune disorders)
  • pyrimethamine (medicine for malaria)
  • digoxin (medicine for heart disease)
This list does not include all medicines that may interact with Sulfamethoxazole + Trimethoprim.

Always notify your doctor and pharmacist if you are taking any other medicines, including herbal tonics such as traditional Chinese medicines, supplements and medicines that you buy without a prescription.
What special dietary instructions should I follow?
Avoid alcohol.
How should I store this medicine?
Store in a cool, dry place away from the reach of children. Protect from light.

Medicines must not be used past the expiry date.
This information is independently developed by MIMS based on sulfamethoxazole + trimethoprim - oral and is provided for your reference only. It is not a replacement for and should only be used in conjunction with full consultation with a licensed healthcare professional, the information provided by your pharmacist and/or the manufacturer of the medication. It may not contain all the available information you require and cannot substitute professional medical care, nor does it take into account all individual circumstances. Although great effort has been made to ensure content accuracy, we shall not be held responsible or liable for any claims or damages arising from the use or misuse of the information contained herein, its contents or omissions, or otherwise. Copyright © 2021 MIMS. All rights reserved. Powered by
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