Bactrim 480 mg Tablets

Brand name

The drug is known under the trade name Bactrim. This is the registered name used to designate this drug on the pharmaceutical market.

International Nonproprietary Name (INN)

The international nonproprietary name of Bactrim is co-trimoxazole. It reflects the combination of two active substances: sulfamethoxazole and trimethoprim, which provide a synergistic antibacterial effect.

Form of release

Bactrim is available in several forms, which allows you to choose the best option for use depending on the age of the patient and the nature of the disease:

• Tablets with a dosage of 400 mg of sulfamethoxazole + 80 mg of trimethoprim (standard dose) and 800 mg + 160 mg (enhanced dose, known as Bactrim Forte).
• Suspension for oral administration with a concentration of 200 mg sulfamethoxazole + 40 mg trimethoprim per 5 mL.
• Solution for infusion (in 5 ml or 10 ml ampoules) containing 80 mg sulfamethoxazole + 16 mg trimethoprim per 1 ml.

The variety of release forms makes the drug convenient for use both in outpatient and inpatient settings.

Composition

Bactrim contains two active ingredients:

• Sulfamethoxazole - a sulfonamide antibiotic that inhibits the synthesis of folic acid in bacterial cells
• Trimethoprim - an inhibitor of bacterial dihydrofolate reductase, enhancing the effect of sulfamethoxazole.

Auxiliary ingredients vary depending on the form of release. In tablets, the following are used:

• Corn starch - binder.
• Lactose monohydrate - filler.
• Magnesium stearate - a lubricating agent.
• Povidone - solvent.

Suspension includes flavorings (e.g., strawberry), sorbitol as a sweetener, cellulose dispersible for structural stability. Solution for infusion contains sodium hydroxide, ethanol and water for injection.

Pharmacologic Properties

Pharmacodynamics

Bactrim has bactericidal action due to the combined effect of two components. Sulfamethoxazole blocks the synthesis of dihydrofolic acid in bacteria, preventing the formation of purines and pyrimidines necessary for the reproduction of microorganisms. Trimethoprim complements this process by inhibiting the enzyme dihydrofolate reductase, which disrupts the conversion of dihydrofolic acid into tetrahydrofolic acid, a key element for the synthesis of DNA and RNA in bacteria. The synergy of these substances makes the drug highly effective against a wide range of pathogens.

Bactrim is active against Gram-positive bacteria (Streptococcus pneumoniae, Staphylococcus aureus) and Gram-negative microorganisms (Escherichia coli, Proteus spp., Klebsiella spp., Haemophilus influenzae). It is also effective against some protozoa, such as Pneumocystis jirovecii.

Pharmacokinetics

The pharmacokinetic parameters of Bactrim ensure its stable therapeutic action.

Absorption

After oral administration, sulfamethoxazole and trimethoprim are rapidly absorbed in the upper gastrointestinal tract. The maximum concentration in the blood is reached in 1-4 hours. Bioavailability is about 90% for both components. Food intake slows absorption but does not reduce overall efficacy.

Distribution

The two substances are well distributed in the body, penetrating the lungs, kidneys, prostate, bile, cerebrospinal fluid and saliva. Sulfamethoxazole binds to plasma proteins by 70%, trimethoprim - by 44%. This ensures sufficient concentration in the foci of infection.

Metabolism

Sulfamethoxazole is metabolized in the liver to form acetylated and glucuronated derivatives, most of which are inactive. Trimethoprim undergoes less metabolism, about 80% is excreted unchanged.

Trimethoprim is metabolized in the liver to form acetylated and glucuronated derivatives.

Excretion

The drug is excreted predominantly by the kidneys through tubular filtration and tubule secretion. The half-life of sulfamethoxazole is 10-12 hours, that of trimethoprim - 8-10 hours. In patients with normal renal function about 60% of the dose is excreted with urine within 24 hours.

Indications for Use

Bactrim is indicated for the treatment of infections caused by co-trimoxazole-sensitive microorganisms. The main indications include:

• Infections of the urinary tract: acute and chronic cystitis, pyelonephritis, urethritis.
• Respiratory infections: bronchitis, pneumonia (including pneumonia caused by Pneumocystis jirovecii).
• Infections of the ENT organs: otitis media, sinusitis, pharyngitis.
• Infections of the gastrointestinal tract: bacterial diarrhea, shigellosis, cholera.
• Infections of the skin and soft tissues: pyoderma, furunculosis.
• Sepsis and other systemic infections caused by sensitive strains.

The drug is often used for the prevention of pneumocystis pneumonia in immunocompromised patients, including HIV patients.

Contraindications

The use of Bactrim is prohibited in the following conditions:

• Hypersensitivity to sulfamethoxazole, trimethoprim or excipients.
• Severe renal insufficiency (creatinine clearance less than 15 ml/min) without the possibility of hemodialysis.
• Severe hepatic insufficiency.
• Megaloblastic anemia associated with folic acid deficiency.
• Pregnancy (especially first trimester) and breastfeeding period.
• Children less than 6 weeks of life (risk of nuclear jaundice).

With caution, the drug is prescribed in glucose-6-phosphate dehydrogenase deficiency and thyroid disease.

Method of Administration and Dosage

How to take

Bactrim tablets are taken orally, drinking plenty of water (at least 200 ml), preferably after meals to reduce gastric irritation. The suspension is shaken before use, measured with a measuring spoon. The solution for infusion is diluted in 0.9% sodium chloride solution or 5% glucose and administered by intravenous drip over 60-90 minutes.

Dosages for adults and children

Dosage is determined by the severity of infection and the age of the patient:

• Adults and children over 12 years of age: standard dose is 400 mg + 80 mg every 12 hours; for severe infections, 800 mg + 160 mg every 12 hours.
• Children 6 weeks - 12 years: 6-8 mg/kg/day trimethoprim (or 30-40 mg/kg/day sulfamethoxazole) divided into 2 doses.
• Pneumocystis pneumonia prophylaxis: 800 mg + 160 mg once daily or 3 times weekly.

Dose adjustment for certain conditions

In renal insufficiency, the dose is adjusted:

• Creatinine clearance 15-30 mL/min: half dose every 12 hours.
• Clearance less than 15 ml/min: use only with hemodialysis.

In hepatic insufficiency, monitoring of the condition is required, but there are no strict guidelines for dose reduction.

Side Effects

Bactrim may cause the following adverse reactions:

• Gastrointestinal: nausea, vomiting, loss of appetite, diarrhea.
• Allergic: rash, itching, rarely - Lyell's or Stevens-Johnson syndrome.
• Hematologic: leukopenia, thrombocytopenia, anemia.
• hepatic: increase in bilirubin, transaminases.
• Renal: crystalluria, interstitial nephritis.

If serious symptoms occur, discontinue use and consult a physician.

Overdose

Symptoms of overdose

Exceeding the dose is manifested by nausea, vomiting, headache, confusion, bone marrow depression, hyperkalemia.

First aid measures

In overdose:

• Stop taking the drug.
• Call for vomiting or gastric lavage (within 1-2 hours).
• Increase fluid intake to prevent crystalluria.
• Seek medical attention.

Hemodialysis is partially effective in eliminating trimethoprim.

Drug Interactions

Bactrim may interact:

• With warfarin - increased anticoagulant effect.
• With metformin - increased risk of lactoacidosis.
• With diuretics (thiazides) - increased risk of thrombocytopenia.

Compatibility with alcohol and food

Alcohol increases toxic effects on the liver and kidneys and should be avoided. Food slows absorption but does not affect efficacy.

Special Precautions

Use in pregnancy and breastfeeding

Bactrim is contraindicated in the first trimester of pregnancy because of the risk of teratogenic effects. In the second and third trimesters it is used only for vital indications. In lactation the drug penetrates into milk, which requires temporary cessation of feeding.

Effect on driving and mechanisms

The drug may cause dizziness or confusion, so driving should be avoided in case of such symptoms.

Particularities of use in the elderly and children

In elderly patients more often side effects occur, especially in case of renal dysfunction. In children, the drug is used with caution, strictly observing the dosage by weight.