Trimethoprim is  an antibiotic drug for treating diseases caused by bacterial infections, such as urinary tract infections and middle ear infections (otitis media).

Trimethoprim works by stopping the growth of bacteria that cause infection. To increase its effectiveness, trimethoprim is usually combined with sulfamethoxazole  . This medicine cannot be used to treat infections caused by viruses, such as the flu.

Trimethoprim trademarks:  Bimactrim, Cotrimaxozole, Cotrim Forte, Decatrim, Etamoxul, Fasiprim, Gencotri, Infatrim, Licoprima, Meprotrin Forte, Moxalas, Omegtrim, Primavon, Pehatrim, Saltrim, Sanprima, Sisoprim, Sultrimmix, Tifatrim, Zecatrim

What is Trimethoprim

class Prescription drug
Category Antibiotics
Benefit Overcome  urinary tract infections and otitis media
Consumed by Adults and Children
Trimethoprim for pregnant and lactating women Category C:  Animal studies have shown an adverse effect on the fetus, but there have been no controlled studies in pregnant women. Drugs should only be used if the expected benefit outweighs the risk to the fetus.

Trimethoprim can be absorbed into breast milk. If you are breastfeeding, do not use this medicine without consulting your doctor first.

Drug form Caplets, tablets and suspension

Precautions Before Taking Trimethoprim

Trimethoprim should only be used as prescribed by a doctor. Here are some things you need to pay attention to before taking trimethoprim:

  • Do not take trimethoprim if you are allergic to this drug. Tell your doctor about any history of allergies you have.
  • Tell your doctor if you have or currently have anemia , kidney disease, liver disease , folic acid deficiency, low blood platelet levels ( thrombocytopenia ), glucose-6-phosphate dehydrogenase ( G6PD ) deficiency, electrolyte disturbances , or  diabetes.
  • Avoid exposure to direct sunlight for a long time, while undergoing treatment with trimethoprim, because this drug can cause the skin to become more sensitive to sun exposure.
  • Tell your doctor if you plan to have life vaccinations, such as the typhoid vaccine, while being treated with trimethoprim.
  • Tell your doctor if you are pregnant, breastfeeding or planning a pregnancy.
  • Tell your doctor if you are taking certain medications, supplements or herbal products.
  • See a doctor immediately if you have an allergic drug reaction , serious side effects, or an overdose after taking trimethoprim.

Dosage and Rules for Using Trimethoprim

The dosage and rules for using trimethoprim are different for each patient. The doctor will give the dose and determine the duration of treatment according to the condition and age of the patient. Here is the explanation:

Purpose: Overcome urinary tract infections

  • Adult: 100 or 200 mg twice daily for 3–14 days.
  • Children aged 4 months to 12 years: 6 mg/kg per day which is divided into 2 consumption schedules.

Purpose: Overcome acute otitis media

  • Children aged ≥6 months: 10 mg/kg per day divided into 2 consumption schedules, for 10 days.

Purpose: Prevent recurrence of urinary tract infections

  • Adult: 100 mg once daily at night.
  • Children 4 months to 12 years: 2 mg/kg, once a day, at night.

How to Take Trimethoprim Correctly

Be sure to follow your doctor 's advice and read the instructions on the drug packaging before taking trimethoprim. Do not add or reduce the dose, and do not use the drug for more than the recommended time.

Take trimethoprim regularly at the same times each day. Trimethoprim tablets and capsules can be taken after meals. Swallow the medicine with the help of a glass of water.

For trimethoprim suspension, don't forget to shake the medicine first before consuming it. Use the measuring spoon provided in the package for a more accurate dosage. Do not use your own measuring device, for example a tablespoon, because the dosage may differ from the recommended one.

If you forget to take trimethoprim, it is recommended to drink it immediately if the break with the next consumption schedule is not too close. If it's close, ignore it and don't double the dose.

Keep taking the drug until the doctor's recommended dose is finished, even though the symptoms have disappeared. Do not reduce the dose, increase the dose, or stop using the drug without a doctor's advice.

If you have diabetes, check with your doctor to monitor your blood sugar levels before and while taking trimethoprim.

Store trimethoprim at room temperature and in a closed container, so that it is not exposed to direct sunlight. Keep this drug out of reach of children.

Interactions  of Trimethoprim with Other Drugs

There are several drug interaction effects that can occur when trimethoprim is used concurrently with other drugs, namely:

  • Increased levels of dapsone in the blood
  • Increased risk of developing folic acid deficiency if taken with folic acid antagonists, pyrimethamine, or anticonvulsant drugs
  • Increased risk of developing anemia due to bone marrow damage when used with methotrexate or azathioprine
  • Decreased effectiveness of trimethoprim when used with rifampicin
  • Increased risk of having low platelet counts when used with diuretic drugs
  • Increased risk of kidney damage when used with ciclosporin
  • Increased risk of bleeding when used with warfarin
  • Increased risk of developing hyperkalemia when used with angiotensin-converting enzyme (ACE) inhibitors , such as captopril

Trimethoprim Side Effects and Dangers

Some of the side effects that can occur after using trimethoprim are:

  • Vomit
  • Diarrhea
  • Stomach ache
  • Swollen tongue
  • Itching and rash
  • No appetite 

Check with your doctor if the side effects above don't go away or get worse. Immediately see a doctor if a drug allergic reaction appears which can be marked by certain symptoms, such as the appearance of an itchy rash, swollen eyes and lips, or difficulty breathing.

In addition, you should also see a doctor immediately if you experience more serious side effects, such as:

  • Severe headache
  • black BAB
  • pale skin
  • Fever
  • Sore throat
  • Sprue
  • Blue fingernails, lips or skin
  • Easy bruising or unusual bleeding
  • Yellowing of the skin and eyes ( jaundice )
  • Joint pain
  • High potassium levels, which is characterized by irregular heartbeat , chest pain, or muscle weakness
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