1 What is Bactrim?

Brand: Bactrim, Bactrim DS, Septra, Septra DS, SMZ-TMP Pediatric, Sulfatrim, Sulfatrim Pediatric

Generic: Sulfamethoxazole and Trimethoprim

Bactrim is an antibiotic. It is used to treat a wide variety of bacterial infections (such as middle ear, urine, respiratory, and intestinal infections).

It is also used to prevent and treat pneumocystis-type pneumonia which occurs more commonly in immunosuppressed patients, such as cancer patients, transplant patients, and patients with acquired immune deficiency syndrome (AIDS).

This is a bactericidal antibiotic along with the broad-spectrum activity. It acts by blocking the synthesis of tetrahydrofolic acid that is essential to the microorganisms.

This combination antibiotic is widely used to treat the following infections because of its broader spectrum of antibacterial activity:

  • Urinary tract infections –due to susceptible strains of Escherichia coli, Klebsiella species, Enterobacter species, Morganella morganii, Proteus mirabilis, and Proteus Vulgaris.
  • Acute otitis media –due to susceptible strains of Streptococcus pneumoniae or Haemophilus influenzae.
  • Acute exacerbations of chronic bronchitis –due to susceptible strains of Streptococcus pneumoniae or Haemophilus influenzae.
  • Shigellosis –a form of enteritis caused by susceptible strains of Shigella flexneri and Shigella sonnei.
  • Pneumocystis jiroveci pneumonia –caused by Pneumocystis jiroveci.
  • Traveler's diarrhea –due to susceptible strains of enterotoxigenic E. coli.

This medicine is available only with your doctor's prescription. This product is available in the following dosage forms:

  • Tablet
  • Suspension

2 What to Know Before Using

Before using Bactrim, you must know all about the risks and complications associated with it. The suitable drug therapy is usually chosen by a doctor with the active participation of the patient.

There are some important factors such as drug interactions, the presence of any metabolic impairment, history of hypersensitivity reaction, pregnancy, lactation etc. which may alter the desired therapeutic effects of a medicine.

Sometimes the presence of other health disorders affects the beneficial effects of this medicine and even may cause serious toxic effects. If you have had any allergic reactions to any medicine then you must tell your doctor about that.

The use of this combination drug is contraindicated in extensive parenchymal liver damage, severe renal insufficiency, blood dyscrasias, pregnancy, a nursing mother, newborn infants, and in those who are hypersensitive to this drug or any of the ingredients of the formulation.

Make sure you inform your doctor if you have any other medical problems, especially:

Because of drug-drug interactions, certain medicines should not be used along with this medicine. It is always recommended to consult with your doctor if you are in need of some other medications or even any over-the-counter medicine for another health problem in order to avoid unwanted toxic effects.

You should keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your physician.

Besides, the following drugs should not be used concurrently because they may interact with this combination drug:

  • Dofetilide
  • Live vaccines
  • Methenamine
  • Methotrexate
  • Phenytoin
  • Rifampicin
  • Rifabutin
  • Tolbutamide
  • Warfarin

There is positive evidence of human fetal risk based on adverse reaction data from investigational or marketing experience or studies in humans, but potential benefits may warrant use of the drug in pregnant women despite potential risks.

Besides, caution should be exercised when used in lactating women because studies in women suggest that this medication poses minimal risk to the infant when used during breastfeeding. An alternative to this medication should be prescribed in such circumstances.

3 Proper Usage

To use Bactrim properly, you must follow all instructions given by your doctor. The dosage schedule and the duration of drug therapy should be individualized and determined based on the physician’s advice. This medicine comes with patient information.

You should read and follow the instructions carefully before using this medicine. The therapeutic dose may vary with the patient’s condition or requirement and the strength of the medicine as well.

You should use this medicine following the directions were given by your doctor, however, different doses of oral dosage form (liquid/tablet) for different indications are listed below:

For treatment of bacterial infections:

  • Adults and children ≥40 kilograms (kg)—800 milligrams (mg) of sulfamethoxazole and 160 mg of trimethoprim every 12 hours for 10 to 14 days. Your doctor may adjust this dose if needed.
  • Children ≥ 2 months of age, and weighing up to 40 kg—Dose is based on body weight and must be determined by your doctor. The usual dose is 40 mg/kg of body weight of sulfamethoxazole and 8 mg/kg of body weight of trimethoprim, given in 2 divided doses every 12 hours for 10 days.
  • Infants < 2 months of age—Use is not recommended.

For treatment of Pneumocystis jiroveci pneumonia or Pneumocystis carinii pneumonia (PCP):

  • Adults and children ≥ 2 months of age—Dose is based on body weight and must be determined by your doctor. The usual dose is 75 to 100 mg/kg of body weight of sulfamethoxazole and 15 to 20 mg/kg of body weight of trimethoprim each day, given in equally divided doses every 6 hours for 14 to 21 days.
  • Children < 2 months of age—Use is not recommended.

For prevention of Pneumocystis jiroveci pneumonia or Pneumocystis carinii pneumonia (PCP):

  • Adults—800 mg of sulfamethoxazole and 160 mg of trimethoprim once a day.
  • Children ≥ 2 months of age—Dose is based on body size and must be determined by your doctor. The usual dose is 750 mg of sulfamethoxazole and 150 mg of trimethoprim per square meter of body surface each day. This is given in equally divided doses two times a day for 3 days a week on consecutive days. However, the dose is usually not more than 1600 mg of sulfamethoxazole and 320 mg of trimethoprim per day.
  • Children < 2 months of age—Use is not recommended.

For traveler's diarrhea:

  • Adults—800 mg of sulfamethoxazole and 160 mg of trimethoprim every 12 hours for 5 days.
  • Children ≥ 2 months of age—Use and dose must be determined by your doctor.
  • Children < 2 months of age—Use is not recommended.

If you miss a dose of this medicine, take it as soon as possible. But, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not use this drug in larger amounts, more often, or for a longer time than your doctor ordered.

Further, it is advised to store the medicine in a closed container at room temperature away from heat, moisture, and direct light. All kinds of medicines should be kept out of the reach of children. However, outdated medicines should be disposed of by an appropriate way.

4 Precautions to Take

Before using Bactrim, there are some precautions you must take. Firstly, regular visits to your doctor are recommended to check that this medicine is working properly or not.

Additionally, the following guidelines should be followed to prevent unwanted complications as well as for the better prognosis of the patients:

Before using this medication, tell your doctor your medical history, especially of: kidney disease, liver disease, certain blood disorders (such as porphyria, anemia due to folate deficiency), severe allergies, asthma, bone marrow suppression, certain metabolic disorders (e.g., G6PD deficiency), underactive thyroid, mineral imbalances (such as high level of potassium or low level of sodium in the blood).

This medication may make you more sensitive to the sun. Avoid prolonged sun exposure, tanning booths or sunlamps. Use a sunscreen and wear protective clothing when outdoors.

If you have diabetes, this product may affect your blood sugar levels. Check your blood sugar levels regularly as directed by your doctor. Tell your doctor right away if you have symptoms of low blood sugar. Your doctor may need to adjust your diabetes medication, exercise program, or diet.

Patients with AIDS may be more sensitive to the side effects of this drug, especially skin reactions, fever, and blood disorders.

This medication is not recommended for use during pregnancy especially near the expected delivery date because of possible harm to the unborn baby. You should use an effective form of birth control to keep from getting pregnant. If you think you have become pregnant while using the medicine, tell your doctor right away.

This medicine, especially if you are receiving high doses or for a long period of time, may lower the number of platelets in your body, which are necessary for proper blood clotting. Because of this, you may bleed or get infections more easily. Talk with your doctor if you have concerns about this.

This medicine may cause diarrhea, and in some cases, it can be severe. It may occur 2 months or more after you stop taking this medicine. Do not take any medicine to treat diarrhea without first checking with your doctor. If you have any questions or if mild diarrhea continues or gets worse, check with your doctor.

This medicine may cause electrolyte problems, such as high potassium in the blood (hyperkalemia) and low sodium in the blood (hyponatremia). Tell your doctor right away if you have any of the following symptoms while using this medicine: confusion, weakness, muscle twitching, an irregular heartbeat, numbness or tingling in the hands, feet, or lips, or trouble breathing.

Before you have any medical tests, tell the medical doctor in charge that you are taking this medicine. The results of some tests may be affected by this medicine.

Patients receiving anticonvulsant therapy (medicines to prevent seizures) may be at risk for a folate (vitamin B9) deficiency, which may increase the risk for side effects. Talk with your doctor if you have concerns about this.

This medication should not be used in children less than 2 months of age due to the risk of serious side effects.

The dosage schedule should be continued until the full prescribed amount is finished, even if symptoms disappear after a few days. Stopping it too early may allow bacteria to continue to grow, which may result in a relapse of the infection.

Do not take other medicines unless they have been discussed with your doctor. This includes leucovorin, other prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

5 Potential Side Effects

As with many medications, there are several potential side effects associated with Bactrim. These side effects usually go away during the treatment episode as your body adjusts to the medicine.

Your healthcare professional may advise you about the ways how to prevent or reduce those unwanted side effects.

Sometimes you may need to consult with the doctor if you notice any of the following toxic effects:

  • Persistent nausea/vomiting
  • Abdominal or stomach pain/cramping
  • Loss of appetite
  • Extreme drowsiness
  • Muscle weakness
  • Mental/mood changes
  • Persistent diarrhea
  • Signs of kidney problems (such as change in the amount of urine, blood in the urine)
  • Signs of low blood sugar (e.g., nervousness, shakiness, sweating, hunger)
  • Persistent headache
  • Persistent cough
  • Neck stiffness
  • Seizures
  • Slow/irregular heartbeat
  • Skin rash/blisters, itching/swelling (especially of the face/tongue/throat)
  • Severe peeling skin rash (such as Stevens-Johnson syndrome)
  • A persistent sore throat or fever
  • Paleness
  • Joint pain/aches
  • Troubled breathing
  • Easy bleeding/bruising/yellowing of eyes or skin
  • Unusual fatigue
  • Blood/mucus in your stool
  • White patches in your mouth

This is not a complete list of possible side effects. If you notice other effects not listed above, check with your healthcare professional.

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