Kombitrim

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Medically reviewed

Marina Burgos

Last updated on 10/01/2026

This page provides general, reference-level information compiled from official medical sources. It is not a substitute for professional medical advice, diagnosis, or treatment. For decisions about your health, please consult a qualified healthcare professional.

Overview of Kombitrim

What is Kombitrim?

Kombitrim is a fixed-dose combination antibiotic medication used to treat a variety of bacterial infections. It contains two active pharmacological agents: sulfamethoxazole and trimethoprim. These two components work together in a synergistic manner to inhibit the growth and reproduction of bacteria.

Mechanism of Action

The effectiveness of Kombitrim is based on its ability to disrupt the production of dihydrofolic acid, a form of folic acid that bacteria require for survival.

  • Sulfamethoxazole: This component interferes with the first step of the bacterial synthesis of folic acid by mimicking a necessary building block called para-aminobenzoic acid (PABA).
  • Trimethoprim: This component blocks a subsequent step in the metabolic pathway by inhibiting a specific enzyme called dihydrofolate reductase.

By targeting two different points in the same metabolic process, the combination is often more effective than either medication used alone and helps to reduce the likelihood of bacteria developing resistance.

Clinical Applications

Kombitrim is utilized for the treatment of several types of infections caused by susceptible organisms. Common applications include:

  • Urinary Tract Infections: Treatment of acute and chronic infections of the bladder and kidneys.
  • Respiratory Infections: Management of conditions such as acute exacerbations of chronic bronchitis and certain types of pneumonia.
  • Gastrointestinal Infections: Use in cases of bacterial dysentery or traveler's diarrhea.
  • Ear Infections: Treatment of acute otitis media, particularly in pediatric populations.

As an antibacterial agent, Kombitrim is only effective against infections caused by bacteria; it does not treat viral infections such as the common cold or influenza.

Regulatory References

  1. World Health Organization’s (WHO) Model List of Essential Medicines
  2. Co-trimoxazole: MedlinePlus Drug Information

What side effects are possible with Kombitrim?

Possible Side Effects and Safety Information

The official safety profile for Kombitrim (Co-trimoxazole), based on regulatory classifications, defines potential adverse reactions by both their frequency and the physiological systems affected. Reactions are formally grouped into System Organ Classes (SOCs), including Blood and Lymphatic System Disorders, Gastrointestinal Disorders, Skin and Subcutaneous Tissue Disorders, and Renal and Urinary Disorders.

Frequency-Classified Adverse Reactions

Adverse effects are categorized by their general incidence as defined in official regulatory documents:

  • Very Common: Nausea and vomiting.
  • Common: Skin reactions such as rash and urticaria, headache, diarrhea, and reversible increases in serum creatinine and blood urea nitrogen (BUN).
  • Rare: Documented reactions include various blood disorders (e.g., leukopenia, agranulocytosis, thrombocytopenia), hepatic effects (hepatitis, cholestasis), and stomatitis.

Serious Adverse Reactions and Safety Considerations

The labeling explicitly documents rare but severe adverse reactions, including life-threatening Severe Cutaneous Adverse Reactions (SCARs) such as Stevens-Johnson syndrome (SJS) and Toxic Epidermal Necrolysis (TEN), as well as severe blood dyscrasias.

Specific safety considerations exist for certain populations. Older adults have a documented increased risk of severe reactions, particularly blood disorders and renal impairment. The drug is contraindicated in individuals with known hypersensitivity to the components, as well as those with severe hepatic parenchymal damage, severe renal insufficiency, or megaloblastic anemia due to folate deficiency.

Regulatory documents also note specific time patterns: for instance, serious skin reactions may appear early in the course of treatment, while blood dyscrasias are more associated with prolonged or high-dose therapy.

Overdose and Emergency Response

Kombitrim (Co-trimoxazole) overdosage is officially documented to present with acute manifestations primarily affecting the gastrointestinal and central nervous systems. Documented symptoms include nausea, vomiting, dizziness, confusion, anorexia, and headache. In severe acute overexposure cases, the patient may become unconscious.

Chronic overdosage or prolonged high-dose exposure is associated with potentially life-threatening systemic outcomes, specifically severe hematopoietic disorders like megaloblastic anemia and bone marrow depression. Serious electrolyte disturbances, such as hyperkalaemia and hyponatraemia, are also documented consequences.

Urgent medical care is required when overdosage is suspected. Immediate medical attention must be sought, and emergency services must be called if the affected person has collapsed, is seizing, or cannot be awakened. Individuals should take the medicine pack or any remaining tablets to the hospital.

Management is largely symptomatic and supportive, and no specific antidote is known for acute poisoning. Official procedures include gastric lavage or inducing emesis to remove unabsorbed drug. For documented myelosuppression, the specific counter-measure is the administration of leucovorin (folinic acid). The elderly and patients with impaired renal function are cited in labeling as being at increased risk for severe complications, necessitating daily monitoring of peripheral blood counts for several weeks following an overdose event.

Therapeutic Uses of Kombitrim

What Kombitrim Treats: Main Uses and Benefits

Kombitrim (a combination of sulfamethoxazole and trimethoprim) is a medication commonly used to address a range of conditions involving certain distressing symptoms. It is applied in clinical settings that involve acute or unstable symptom patterns, helping to manage discomfort and symptoms that interfere with daily functioning associated with these conditions.

The medicine is used for managing conditions presenting with acute episodes and recurrent manifestations, including those associated with systemic or localized discomfort and episodic symptom patterns.


Easing Episodic Symptom Discomfort

This therapeutic domain is relevant for easing symptoms, particularly when groups of symptoms appear or fluctuate. Kombitrim supports patients during difficult episodes by easing distress and is relevant for easing symptoms related to inflammatory or irritative states that interfere with daily comfort. It contributes to easing the overall symptom load.


Supporting Functional Stability

Kombitrim is applied across domains where additional symptomatic support is needed, often in conditions where functional stability becomes affected due to heightened physiological activity. It is used in settings where short-term symptom stabilization is important, supporting general well-being when symptoms create noticeable physiological strain and become more noticeable.

Quick Fact: Used for Fluctuating Symptoms


Addressing Acute and Recurrent Symptom Patterns

This medication is applicable in scenarios where additional management of discomfort is required, offering symptomatic relief that helps patients cope more steadily with symptom fluctuations linked to organ-specific functional stress. It is commonly used when symptoms intensify and supportive relief is needed.

Regulatory References

  1. NIH MedlinePlus overview of Co-trimoxazole

Eligibility and Restrictions for Use

Who Can and Cannot Use Kombitrim (Co-trimoxazole)

Official regulatory guidelines define specific populations that are eligible, restricted, or absolutely prohibited from using Kombitrim, a combination of sulfamethoxazole and trimethoprim.

Absolute Contraindications

Kombitrim is contraindicated (must not be used) in patients with known hypersensitivity to trimethoprim or sulfonamides. Absolute non-eligibility also applies to patients with documented megaloblastic anemia due to folate deficiency, severe hepatic damage, or severe renal insufficiency where function cannot be monitored. Additionally, it is prohibited for use with the medication dofetilide.

Age- and Condition-Based Restrictions

Population Group Regulatory Status and Constraint
Infants Contraindicated in pediatric patients less than 2 months of age [Age Restriction].
Pregnant Patients Contraindicated at term (late stage) and Not Recommended during the first trimester [Reproductive Status].
Nursing Mothers Contraindicated [Reproductive Status].
Renal Impairment Restricted Use: Requires a 50% dose reduction for patients with moderate impairment (CrCl 15 to 30 mL/min) [Organ Function].
G6PD Deficiency Conditional Use: Use is advised with caution due to the risk of hemolytic anemia [Metabolic Status].

Use is established in adults and pediatric patients two months of age and older. Older adults are advised to use the medication with caution due to an increased risk of specific adverse effects, particularly when also taking thiazide diuretics.

What should I know about interactions with other medicines?

Kombitrim Interactions with other medicines and products

Kombitrim (Co-trimoxazole) may interact with a range of other medicines and products, necessitating formal restrictions and careful management as documented in regulatory information. This section outlines officially documented interaction patterns.

Formal Contraindicated Combinations

Co-administration is formally prohibited with agents such as Dofetilide and Levomethadyl due to significant risks documented in prescribing information.

Pharmacokinetic and Exposure Alterations

Kombitrim affects the body's processing of several critical medicines, primarily through metabolic inhibition and transporter interference:

  • Anticoagulants: It potentiates the effect of Warfarin by inhibiting its metabolism, necessitating monitoring.
  • Phenytoin: The combination prolongs the half-life of Phenytoin through metabolic inhibition, increasing its exposure.
  • Digoxin: Trimethoprim can increase the plasma levels of Digoxin, particularly in elderly patients.
  • Lamivudine and Procainamide: The trimethoprim component interferes with renal tubular secretion, leading to increased exposure of these drugs.

Pharmacodynamic and Other Interactions

  • Potassium-Sparing Drugs: Co-administration with agents like ACE Inhibitors or Spironolactone may result in clinically relevant hyperkalaemia (increased potassium levels).
  • Anti-folate Drugs: Concurrent use of high-dose Pyrimethamine or Methotrexate carries a risk of additive anti-folate effects.
  • Diuretics (Thiazides): An increased risk of thrombocytopenia is documented in elderly patients using this combination.
  • Non-Medicinal Agents: Ethanol (alcohol) is generally not recommended for co-use, and Folinic Acid supplementation is noted to interfere with the antimicrobial efficacy.

Mechanism of Action

How Kombitrim Works

Kombitrim (Co-trimoxazole) functions through a precise, dual-target mechanism that interferes with the ability of susceptible bacteria to synthesize essential metabolic components, resulting in a synergistic metabolic blockade.

Sequential Enzyme Blockade and Selectivity

The drug sequentially blocks two consecutive enzymes: Sulphamethoxazole acts as a competitive inhibitor of dihydropteroate synthase (DHPS), and Trimethoprim acts as a reversible inhibitor of dihydrofolate reductase (DHFR). This mechanism exhibits high selectivity, as the drug components inhibit the bacterial enzymes with significantly greater affinity than those found in human cells.

Collapse of the Folate Synthesis Pathway

The dual inhibition causes a critical deficit of tetrahydrofolic acid (THF), an essential coenzyme. This collapse in the folate biosynthesis cascade leads directly to the complete cessation of purine and thymidine precursor synthesis. The resulting lack of DNA and protein building blocks causes a bactericidal action on the susceptible organisms, a mechanism distinct from bacteriostatic effects.

Dosage and Administration Information

How to Use Kombitrim (Co-trimoxazole) — Administration Guidelines

Kombitrim, a fixed-dose combination of Sulfamethoxazole (SMX) and Trimethoprim (TMP), must be administered according to specific, documented instructions to ensure proper use.


Dosing Routes and Frequency

Kombitrim is approved for two primary routes of administration: oral (using tablets or suspension) and intravenous (IV) infusion. The standard schedule for most acute infections involves administering the drug every 12 hours.

  • Oral Intake: Tablets are generally recommended to be taken with some food or drink to minimize potential gastrointestinal upset. Patients should maintain sufficient water intake during the course of treatment.
  • IV Infusion Protocol: The concentrate for injection must be diluted in 5% Dextrose in Water or other specified solutions prior to use. The diluted solution must be given as an infusion over a period of 60 to 90 minutes; rapid infusion or bolus injection is strictly forbidden.

Dosage and Duration Principles

Instruction Domain Guideline
Standard Adult Dose 800 mg SMX / 160 mg TMP (Double-Strength tablet) every 12 hours.
Pediatric Use Prohibited for use in infants under two months of age. Dosing for children 2 months and older is weight-based.
Renal Impairment Requires dose adjustment based on Creatinine Clearance (CrCl). If CrCl is 15–30 mL/min, administer half the usual regimen. Use is not recommended if CrCl is below 15 mL/min.
Treatment Duration Treatment should continue until the patient has been symptom-free for two days, typically requiring a minimum of 5 days of therapy. Severe infections, such as PJP, require longer courses (e.g., 14 to 21 days).

These instructions establish that the drug's effective delivery depends on accurate dose adjustment for kidney function and strict adherence to the prescribed frequency, duration, and infusion rate.

Recent Clinical Evidence

Kombitrim: Recent Clinical Evidence

Evidence Supporting Established Uses

The research foundation for Kombitrim (Co-trimoxazole) is rooted in historical Randomized Controlled Trials (RCTs) and systematic reviews. For Pneumocystis Pneumonia (PJP), studies monitored changes in patient survival and were evaluated as part of long-term regimens to monitor the condition’s occurrence, primarily in immunocompromised individuals. This research contributes to the broader evidence landscape for prophylaxis.

Kombitrim was also evaluated in comparative trials exploring acute Urinary Tract Infections (UTIs). These studies explored outcomes related to physical discomfort, focusing on the clearance of bacteria and the evolution of perceived discomfort. However, findings are mixed across studies, as data show patterns related to regional differences in bacterial antimicrobial resistance that may affect consistency.

For Melioidosis, Kombitrim was studied for use in the prolonged oral treatment phase. These RCTs monitored patients for recurrence for a year after the oral course was finished. Research is still exploring the ideal duration of this prolonged phase, as evidence quality varies across trials.

Research Gaps and Uncertainty

Most research explores short-term outcomes. Long-term effects and the durability of response are generally not fully established, and follow-up durations were limited after study endpoints were reached. Evidence for special populations is often insufficient; for instance, subgroup findings for certain older adult groups remain uncertain. Furthermore, comparative evidence is lacking when evaluating Kombitrim against other standard agents for some indications, and data for certain groups remain insufficient, highlighting areas where further research is ongoing.

Key Studies & References

  1. Co-trimoxazole (sulfamethoxazole and trimethoprim) monograph and uses
  2. WHO Model List of Essential Medicines - Co-trimoxazole inclusion
  3. Trimethoprim-sulfamethoxazole for the prevention of Pneumocystis carinii pneumonia in HIV-infected patients

Frequently Asked Questions (FAQ)

Common questions about Kombitrim (FAQ)

Q: What is Kombitrim used for in simple terms?

A: Kombitrim is classified as an anti-infective agent, meaning its primary purpose is to treat or prevent certain bacterial infections. Official documents indicate its use for specific infections of the urinary tract, lungs, ears, skin, and gastrointestinal system.

Q: What are the most common reasons doctors prescribe Kombitrim?

A: According to regulatory documents, common approved uses for Kombitrim include treating urinary tract infections and acute middle ear infections. It is also documented for use against traveler’s diarrhea and for the treatment and prevention of Pneumocystis Pneumonia (PJP).

Q: Do I need to avoid certain foods or drinks while taking Kombitrim?

A: Official prescribing information states that the co-use of ethanol (alcohol) is generally not recommended while taking this drug. However, official documents do not list any specific foods that must be strictly avoided during the course of treatment.

Q: Are there any long-term side effects associated with Kombitrim use?

A: Official summaries of clinical evidence note that most research focuses on short-term outcomes. The long-term effects and the durability of the response following treatment are generally not fully established, as follow-up durations in studies were limited.

Q: Can Kombitrim interact with common supplements like multivitamins?

A: Official drug labels note that Kombitrim is documented to interfere with the efficacy of Folinic Acid supplementation. Information regarding interactions with other general multivitamins is not specifically detailed in regulatory documents.

Q: What is the risk of an allergic reaction to Kombitrim?

A: The official safety profile for Kombitrim documents hypersensitivity and life-threatening Severe Cutaneous Adverse Reactions (SCARs) as rare but serious safety concerns. These types of reactions are highlighted as requiring prompt attention in regulatory information.

Q: Is Kombitrim available over the counter in any country?

A: Kombitrim is classified by the FDA as a prescription-only medicine in the United States. Its classification in the US means it is restricted to dispensing under a valid prescription.

Q: Are there any known interactions with herbal supplements and Kombitrim?

A: Official patient counseling information emphasizes the importance of informing healthcare providers about all medicines being taken, including any herbal products. This disclosure is advised due to the potential for undocumented interactions.

Q: Why is it important to take the full course of Kombitrim (general reason)?

A: Official patient counseling describes the practice of completing the full course of treatment as it helps to decrease the likelihood that bacteria will develop resistance and maintain the effectiveness of the drug for future use.

Q: What happens if Kombitrim is stopped too early (general expectation)?

A: Official patient counseling states that stopping treatment too soon or skipping doses may decrease the effectiveness of the treatment. This action also increases the likelihood that the bacteria will develop resistance.

Q: Is Kombitrim widely prescribed globally?

A: Kombitrim’s active ingredients are included on the World Health Organization’s (WHO) Model List of Essential Medicines, which reflects its global recognition as an essential anti-infective agent.

Q: What are common patient concerns about Kombitrim's side effects?

A: According to official safety documents, the most frequently reported adverse reactions include nausea, vomiting, headache, and diarrhea. These are categorized as Very Common or Common adverse events.

Q: How quickly does Kombitrim start working after you take it?

A: Official data on drug absorption indicates the drug is rapidly absorbed following oral intake. Peak blood levels are typically reached within 1 to 4 hours, and steady-state levels are generally achieved after three days of administration.

Q: Is it true that Kombitrim can cause sun sensitivity?

A: The official safety profile for the drug is documented to include the potential for photosensitivity reactions. These reactions may resemble severe sunburn and may occur in areas of skin exposed to sunlight.

Q: What should I do if I miss a dose of Kombitrim (general, non-directive)?

A: General instructions describe taking a missed dose as soon as possible. However, if it is nearly time for the next scheduled dose, the missed dose is described as being skipped entirely. Double doses are advised against.

Q: Does Kombitrim affect birth control pills?

A: Regulatory documents note that the sulfamethoxazole component of Kombitrim may reduce the effectiveness of some hormonal contraceptives. This effect is seen in products that contain ethinyl estradiol.

Q: What is the difference between Kombitrim and a penicillin-type drug?

A: Kombitrim works by sequentially blocking two steps in the bacterial production of folic acid, a necessary compound for growth. In contrast, penicillin-type drugs function by interfering with the synthesis of the bacterial cell wall.

Q: Does taking Kombitrim affect sleep or cause insomnia?

A: Regulatory documents list insomnia and other sleep problems as potential neurological side effects associated with the drug. This type of effect is noted in the official safety profile.

Q: Is it normal to feel tired while taking Kombitrim?

A: Fatigue is noted in regulatory profiles as a possible neurological side effect. This type of reaction is part of the official safety documentation.

Q: Is Kombitrim used to treat skin infections?

A: Official labeling includes an indication for the treatment of certain skin and soft tissue infections. Its use in this area targets infections caused by susceptible bacteria.

Q: Do I need a prescription from a doctor to get Kombitrim?

A: Kombitrim is consistently classified by the FDA and other regulatory bodies as a prescription-only medicine. Its classification means that it is not available for purchase over the counter.

Q: Is it okay to take Kombitrim if I have diabetes?

A: Kombitrim is documented to affect blood glucose levels and may potentiate the effects of certain oral hypoglycemic medicines. Regulatory information indicates that patients with diabetes may require careful monitoring.

Q: Does Kombitrim have a boxed warning in official documents?

A: Official prescribing information highlights serious adverse reactions, including life-threatening skin reactions and blood dyscrasias. These severe safety risks are prominently noted in the official drug documentation.

Q: Are generic versions of Kombitrim available?

A: Yes, the FDA has approved generic versions of the sulfamethoxazole and trimethoprim combination product. The FDA has approved generic versions, which contain the same active ingredients.

Q: How long does Kombitrim stay in your system?

A: Clinical pharmacology data shows that the mean serum half-lives of the two active components, sulfamethoxazole and trimethoprim, are approximately 10 hours and 8 to 10 hours, respectively. The length of time a drug remains in the system is related to its half-life.

Q: Is Kombitrim a first-line or second-line treatment?

A: Regulatory-cited consensus guidelines recommend Kombitrim as a first-line agent for the prophylaxis (prevention) of certain opportunistic infections. This is often seen for conditions such as Pneumocystis Jirovecii Pneumonia (PJP).

Q: Can men and women use Kombitrim for the same conditions?

A: The approved indications for Kombitrim are generally not differentiated based on patient gender. The drug is indicated for conditions such as urinary tract infections and chronic bronchitis, regardless of whether the patient is male or female.

Q: Does Kombitrim treat things other than infections?

A: The primary purpose of Kombitrim, as defined in regulatory documents, is to function as an anti-infective agent. All approved indications for the drug are focused on treating and preventing susceptible bacterial infections.

How should Kombitrim be stored and disposed of?

Kombitrim, containing sulfamethoxazole and trimethoprim, must be stored properly to maintain its stability and effectiveness. The tablets should be kept in the container it came in, tightly closed, and stored at room temperature away from excess heat and moisture. Keep it out of direct light. The labeled storage condition is typically Controlled Room Temperature, between 68°F and 77°F (20 C and 25 C). The medication should be dispensed in a tight, light-resistant container. Always keep this and all medications out of the sight and reach of children.

For disposal, do not flush unused tablets down the toilet or pour them down a sink unless specifically instructed by the manufacturer's label. To safely discard unneeded medicine, follow the FDA's general guidance: mix the tablets with an unappealing substance like dirt or used coffee grounds, place the mixture in a sealed plastic bag, and throw it in the household trash. You may also check for local medication take-back programs.

Attention! Always consult to a doctor or pharmacist before using pills or medicines.

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