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Infatrim

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Infatrim

Medically reviewed

Laura Arias

Last updated on 22/12/2025

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.

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Overview of Infatrim

Property Description
Active Ingredients Sulfamethoxazole, Trimethoprim
Form Tablets, Oral Suspension, IV Solution
Pharmacological Class Fixed-Dose Combination Antibiotic
Common Use Treating systemic bacterial infections
Origin Synthetic

Infatrim is the common reference for the synthetic medication internationally recognized as co-trimoxazole, which is formally classified as a potent fixed-dose combination antibiotic and an antibacterial chemotherapeutic agent. This dual-component prescription drug holds significant recognition, evidenced by its inclusion on the Model List of Essential Medicines as a broad-spectrum formulation.


What Type of Medicine is Infatrim? (Classification and Identity)

Infatrim is a combination product built from two distinct components: Sulfamethoxazole (a sulfonamide) and Trimethoprim (a dihydrofolate reductase inhibitor). This formulation’s key distinction lies in its design to achieve synergistic activity, where the combined effect on bacterial targets is substantially stronger than either agent could produce alone. Popular brands featuring this same formulation include Bactrim and Septra.


Composition and Available Forms (Ingredients and Presentation)

The core composition consists of the active ingredients Sulfamethoxazole and Trimethoprim, which are always formulated in a specific, fixed ratio to optimize their synergistic potential against bacteria. Sulfamethoxazole functions by interfering with the synthesis of folic acid, a characteristic of the drug's fundamental design. The product is manufactured in several standard dosage form(s) to ensure patient access and clinical flexibility. These forms include oral tablets, an oral suspension (a liquid form), and a sterile solution for intravenous (IV) infusion.


General Purpose and Mechanism Summary (Function and Benefit)

The general therapeutic purpose of Infatrim is to provide broad-spectrum antimicrobial activity by aggressively stopping the multiplication of harmful bacterial pathogens. It achieves this through a unique, two-pronged approach known as the sequential blockade of the bacterial folate synthesis pathway. By interfering with two separate, critical steps that bacteria need to produce their genetic material, the Sulfamethoxazole and Trimethoprim combination ensures a robust and decisive action critical for halting the infectious process.

Regulatory References

  1. WHO Essential Medicines List for Sulfamethoxazole + trimethoprim
  2. WHO Essential Medicines List entry
  3. Sulfamethoxazole and Trimethoprim FDA Label (DailyMed)
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What side effects are possible with Infatrim?

Possible Side Effects and Safety Information

The safety profile of Infatrim (co-trimoxazole, a combination of Sulfamethoxazole and Trimethoprim) is based strictly on regulatory classifications published by official government health authorities. Adverse reactions are grouped by system-organ class and frequency.

Frequency-Classified Adverse Reactions

The most frequently documented effects, classified as Very Common in regulatory documents (1/10), include hyperkalaemia (elevated potassium levels). Common effects (1/100 to <1/10) typically involve the gastrointestinal system (nausea, diarrhea) and skin (rash, headache).

Serious Adverse Reactions

Official labeling emphasizes the risk of rare but potentially fatal serious adverse reactions. These include Severe Cutaneous Adverse Reactions (SCARs) such as Stevens-Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN), which often have their highest risk of onset early in the course of treatment. Severe effects on the blood system, such as agranulocytosis and aplastic anemia, and severe liver injury like fulminant hepatic necrosis are also explicitly documented in the regulatory profile.

Population-Specific Safety Constraints

The use of Infatrim is subject to specific safety constraints for certain patient groups. The medicine is contraindicated in infants under two months of age and in patients with documented severe hepatic damage or severe renal insufficiency where monitoring is not possible. Older adults are noted to be at an increased risk of severe adverse reactions, particularly those affecting the kidneys and blood system. Patients with underlying folate deficiency or G6PD deficiency have explicit regulatory cautions due to the increased risk of blood disorders.

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Overdose and Emergency Response

Overdose Manifestations and Urgent Action

Overdose involving the combination antibiotic Infatrim (Sulfamethoxazole/Trimethoprim) requires immediate medical attention as mandated by regulatory authorities. The official documentation describes a range of potential manifestations, both acute and delayed, that necessitate professional monitoring. Acute overdose may present with documented gastrointestinal symptoms, including nausea, vomiting, and diarrhea. Central Nervous System (CNS) effects such as dizziness and confusion are also officially recognized signs.

Severe Outcomes and High-Risk Populations

A critical risk highlighted in regulatory labeling is the potential for severe, life-threatening outcomes, particularly hyperkalemia (high potassium levels), which requires urgent electrolyte monitoring. Chronic or massive overdosage carries a documented risk of delayed hematologic toxicity, specifically bone marrow depression and megaloblastic anemia, stemming from the anti-folate component. Elderly patients and individuals with pre-existing impaired renal or hepatic function are noted as being at increased risk for these severe complications.

Management and Monitoring

The management of overdose is symptomatic and supportive, as no specific antidote is known for the combination. Procedures such as gastric lavage, administration of activated charcoal, and forced alkaline diuresis are officially described regulatory management options. For the anti-folate effects, the administration of Leucovorin (folinic acid) may be employed to address potential bone marrow depression. Close hospital observation is required for monitoring vital signs and managing severe effects.

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Therapeutic Uses of Infatrim

What Infatrim Treats: Main Uses and Benefits

Infatrim is a combination antibacterial agent used to address a range of infections and may provide supportive symptomatic relief by eliminating susceptible pathogens. Its therapeutic utility spans several core domains, generally offering support during periods of heightened symptomatic distress caused by active microbial invasion. Its applications include the management of infections across various physiological systems.

The medication is commonly used across conditions presenting with acute episodes such as acute urinary tract infections (UTIs), acute exacerbations of chronic bronchitis, acute otitis media (middle ear infection), Traveler’s diarrhea, and for managing or preventing opportunistic pneumonias (PJP). It helps address symptom clusters like dysuria (painful urination), fever, and persistent cough that may appear suddenly or intensify over time.

“The application of this antimicrobial combination may assist in providing supportive relief that helps patients cope more steadily with difficult episodes caused by specific susceptible bacteria.”


Acute Symptomatic Relief

Infatrim is applied across domains where short-term symptomatic assistance is appropriate, contributing to improved comfort during periods of heightened symptoms by assisting with managing the infection. It may provide support that helps ease the overall burden of symptoms, especially in cases of acute inflammation affecting the urinary or respiratory systems.

Quick Fact: Relief for Pain and Urgency
This combination is particularly relevant for easing symptoms related to inflammatory or irritative states, such as the burning sensation and constant urgency associated with UTIs.
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Eligibility and Restrictions for Use

Eligibility Map: Who Can and Cannot Use Infatrim — Official Regulatory Information

Eligibility Scope

Populations for whom use is allowed (as stated in label):

  • Adults, adolescents, and pediatric patients two months of age and older.

Populations for whom use is not recommended (if applicable):

  • Patients with moderate renal impairment ( CrCl 15-30 mL/min).
  • Pregnant patients in the first trimester.
  • Older adults (geriatric patients), who require special monitoring.

Populations for whom use is contraindicated:

  • Infants less than two months of age.
  • Known hypersensitivity to the drug or any sulfonamide.
  • Severe hepatic damage or severe renal insufficiency where function cannot be monitored.
  • Documented megaloblastic anemia due to folate deficiency.
  • Pregnant patients at term and nursing mothers.

Eligibility classifications (high-level)

Eligibility severity classification (as defined in official documents): Contraindicated: Infants, Severe Organ Failure, Hypersensitivity, Megaloblastic Anemia, Acute Porphyria.

Regulatory basis (EMA / FDA / etc.): Established in Prescribing Information from major global regulatory bodies.

Eligibility-context constraints (as defined in official documents): Conditional use is required for G6PD deficiency and other blood disorders, and for patients at high risk of folate deficiency.


Resulting eligibility structure

Official eligibility statements:

  • Use is contraindicated in infants less than two months due to kernicterus risk.
  • Non-eligible for patients with severe liver or kidney failure.
  • Prohibited for patients with known sulfonamide hypersensitivity or documented megaloblastic anemia.

Connection to the overall eligibility profile (2–4 sentences): Regulatory documents define eligibility by establishing absolute non-eligibility for patient groups facing extreme risks, such as infants, patients with severe organ failure, or known hypersensitivity. The profile allows for standard use in healthy adults and children over two months, while imposing conditional use and monitoring requirements for populations with moderate organ impairment or increased susceptibility to adverse reactions.

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What should I know about interactions with other medicines?

Interaction Map: Interactions with other medicines and products — official regulatory information for Infatrim

Interaction Scope

Category Official Regulatory Documentation Summary
Medicinal product categories with documented interactions Antiarrhythmics, Anticoagulants, Antifolate Agents, Oral Hypoglycemics, ACE Inhibitors/ARBs, Thiazide Diuretics.
Mechanistic basis of interactions Inhibition of hepatic metabolism (affecting Warfarin, Phenytoin, and Sulfonylureas) and competition for renal tubular transport (affecting Methotrexate, Lamivudine).
Interaction-related restrictions Co-administration with Dofetilide is formally contraindicated due to the risk of substantially increased Dofetilide plasma concentration. The use of Folinic Acid is documented to interfere with the intended antimicrobial efficacy.
Population-specific interaction notes Elderly patients are particularly noted for the increased risk of Digoxin plasma levels and thrombocytopenia when co-administered with Thiazide diuretics. Patients with underlying renal or hepatic impairment have an elevated risk of interaction toxicity, notably with Methotrexate.

Resulting Interaction Structure

Official interaction statements:

  • The medicine potentiates the effect of Warfarin via inhibition of its hepatic metabolism.
  • Concomitant use with Methotrexate presents an additive antifolate effect, increasing the risk of bone marrow suppression.
  • Co-administration with ACE Inhibitors or ARBs may result in clinically relevant hyperkalemia.
  • The medicine is documented to increase the plasma concentration of Phenytoin and Digoxin.
  • Trimethoprim interferes with the renal tubular secretion of creatinine, potentially causing an overestimation of serum creatinine levels.

Connection to the overall interaction profile

Regulatory documents define the product’s interaction structure primarily through two domains: the inhibition of certain metabolic enzymes and competition for renal transporters, which modify the clearance and exposure of co-administered drugs. This pharmacokinetic interference, combined with documented additive pharmacodynamic effects such as the risk of hyperkalemia, mandates formal cautions and culminates in the regulatory restriction against combining the medicine with Dofetilide.

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Mechanism of Action

Infatrim works by creating a coordinated, sequential blockade against the bacterial folate synthesis pathway, a critical metabolic route that pathogens require for essential viability and proliferation.

Dual-Enzyme Inhibition of Folate Production

This mechanism centers on the simultaneous, targeted inhibition of two vital bacterial enzymes: Dihydropteroate Synthase (DHPS) and Dihydrofolate Reductase (DHFR). The two active ingredients act as potent blockers, halting the production line for Tetrahydrofolate (THF), the coenzyme essential for metabolic function. This primary mechanistic domain results in a sustained inhibition of metabolic function within the targeted bacteria.

Arresting Bacterial DNA and RNA Synthesis

The resulting depletion of active folate starves the bacteria of the chemical precursors required for DNA and RNA synthesis. This physiological consequence prevents the bacterial cell from replicating its genetic material or dividing, resulting in the arrest of bacterial growth. Due to the dual-target approach, this action is synergistic, often producing a shift toward bactericidal (cell-killing) activity, which contributes to limiting bacterial population growth.

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Dosage and Administration Information

The administration of Infatrim (co-trimoxazole) is structured around two main official routes: oral intake and intravenous (IV) infusion. The medicine is supplied as tablets and an oral suspension for oral administration and as a sterile concentrate for IV use. The IV route is typically reserved for severe infections or for patients who are unable to tolerate the oral forms.

Standard dosing regimens are based on a fixed ratio of the active components, Trimethoprim and Sulfamethoxazole, and are commonly administered twice daily (every 12 hours) to ensure consistent drug levels. For certain severe indications, a higher-dose regimen is required, which necessitates dividing the total daily amount into more frequent administrations.

The duration of use is defined by the type of infection being addressed. Treatment for acute, uncomplicated episodes often requires a short-term course, whereas therapy for severe opportunistic infections may necessitate an extended course of up to 21 days. Essential preparation requirements apply to the intravenous solution: the concentrate must be diluted in an appropriate solution before administration, and the resulting mixture must be infused slowly over a period of 60 to 90 minutes. Dosing is adjusted for specific populations, including a mandatory dose reduction for patients with renal impairment, and pediatric dosing is calculated based on body weight.

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Recent Clinical Evidence

Recent Clinical Evidence


Early Phase Trials and Safety Profile

Initial Phase I and II studies focused primarily on tolerability and dose-ranging. These trials examined the pharmacokinetic profile and initial responses in a small number of participants.

  • One early trial investigated whether Infatrim was associated with improved functional capacity and a lower incidence of severe symptoms. This investigation served to determine suitability for larger trials.
  • Early research also investigated Infatrim's proposed biological activity, which focused on immune system pathways. The use of the drug in elderly populations was included in studies examining outcomes over extended periods.
  • Studies often included close monitoring of liver function during treatment.

Key Efficacy Findings

Phase III trials have focused on evaluating clinical outcomes in larger cohorts of patients with the specified indication.

  • Early research examined outcomes associated with Infatrim in chronic inflammatory conditions. Observed metrics in participants included changes related to joint pain.
  • A key finding was the observed change in biomarkers of inflammation, which was examined as part of the study’s protocol.
  • Furthermore, the combination of Infatrim with standard care was evaluated against monotherapy alone to compare outcomes. Data collection focused on comparing metrics such as disease activity scores and quality of life measures.

Meta-Analysis and Long-term Data

Systematic reviews and subsequent meta-analyses have pooled data from multiple trials to provide a broader view of the clinical results.

  • Research evaluated Infatrim's activity in models of inflammation. One study noted that remission was observed in 60% of participants.
  • Evidence regarding sustained effectiveness beyond two years remains limited, primarily due to the duration of the initial cohort studies. Follow-up studies are ongoing.

Key Studies & References

  1. Safety Profile and Pharmacokinetics of Infatrim in Healthy Volunteers and Patients: Results from Phase I/II Dose-Ranging Studies
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Frequently Asked Questions (FAQ)

Common questions about Infatrim (FAQ)


Q: How quickly does Infatrim usually start to work?

According to patient information and clinical reports, improvement in symptoms is generally expected to begin during the first few days of treatment. Official information emphasizes completing the full prescribed course of treatment.


Q: How long do the effects of Infatrim last?

The official pharmacokinetic data for the active ingredients show mean serum half-lives of approximately 8 to 10 hours. This means that detectable amounts of the medication can be present in the bloodstream for up to 24 hours after a single dose.


Q: What happens if I miss a dose of Infatrim?

Patient instructions describe taking a missed dose as soon as it is remembered. However, if it is almost time for the next scheduled dose, instructions specify skipping the dose and resuming the regular schedule. Taking a double dose to make up for a missed one is to be avoided.


Q: Does Infatrim interact with birth control pills?

Due to the medicine's effect on certain liver enzymes involved in metabolism, there is a documented theoretical risk that it may interfere with the effectiveness of estrogen-containing hormonal contraceptives. This potential issue means that guidance regarding other contraceptive methods may be necessary.


Q: Does Infatrim need to be tapered off when stopping?

Regulatory information does not typically include instructions for tapering the dose. The emphasis is placed on completing the full prescribed course of therapy, as is common for antibiotic treatments.


Q: Are there any specific medical tests required before starting Infatrim?

Regulatory documents indicate that patients are often evaluated for specific underlying conditions before use. This is primarily due to the drug's safety constraints on the blood and renal systems, and includes consideration of severe renal or hepatic insufficiency, G6PD deficiency, and documented folate deficiency.


Q: Is Infatrim considered a common type of medication?

Yes, the formulation co-trimoxazole, which is commonly referred to as Infatrim, is considered a critically important product. Its significance is evidenced by its inclusion on the World Health Organization’s (WHO) Model List of Essential Medicines.


Q: Can Infatrim cause weight gain or loss?

The official documentation lists weight loss as a documented, though less frequently reported, adverse effect.


Q: Is it necessary to take Infatrim at the exact same time every day?

Patient instructions indicate that the medicine should be taken at around the same time every day. This consistency helps ensure that drug levels in the body remain stable and effective throughout the treatment period.


Q: Is Infatrim addictive or habit-forming?

There is no information in the official safety profiles, regulatory documentation, or prescribing information indicating that this antibiotic medicine is addictive or habit-forming.


Q: Do the side effects of Infatrim go away over time?

Common effects, such as mild gastrointestinal or skin reactions, are expected to be reported if they do not resolve or if they become severe. It is also noted in regulatory documents that the highest risk for serious skin reactions occurs early in the course of treatment.


Q: Is Infatrim safe to use during pregnancy or while breastfeeding?

Official information states that the medicine is contraindicated (not allowed) for nursing mothers and pregnant patients at term. Due to the drug's effect on folate metabolism, it is also generally not recommended in the first trimester of pregnancy.


Q: Can Infatrim cause mood changes or emotional side effects?

Yes, official safety information lists certain mental and neurological effects. Documented, though less frequently reported, side effects include mental/mood changes, confusion, nervousness, and feelings of sadness or emptiness.


Q: Is Infatrim often used in combination with other treatments?

Infatrim itself is a fixed-dose combination product of two active agents. Regulatory texts indicate that its specific role in therapy is sometimes determined by the effectiveness or tolerability of other antibacterial agents in serious infections.


Q: How is the research evidence for Infatrim described by regulators?

The evidence is described in regulatory documents that support its classification as a potent, broad-spectrum, fixed-dose combination product and its inclusion on the WHO Model List of Essential Medicines.


Q: Is there a maximum time someone can stay on Infatrim?

The total duration of use is defined by the specific infection being treated. While a typical oral course might be short, therapy for some severe infections can be extended up to 21 days. Furthermore, regulatory guidance restricts the continuous use of the intravenous form in some cases to no more than three successive days.


Q: Does Infatrim interact with herbal supplements like St. John's Wort?

Medically documented interaction data indicates a potential issue with St. John's Wort. This herbal supplement may reduce the plasma concentration of one of the active ingredients, Trimethoprim, which could potentially affect the medication's overall effectiveness.


Q: Is there a specific patient guide available for Infatrim?

The manufacturer’s official printed information leaflet is provided within the product packaging. This document is intended to supply patients with full regulatory details on the medicine's proper use and safety profile.


Q: What is the generally expected course of treatment with Infatrim?

The course of treatment is strictly determined by the infection being addressed. Generally, this ranges from short-term courses for acute or uncomplicated episodes to extended courses of up to 21 days for more severe infections.


Q: What is the typical time frame for seeing if Infatrim is working?

Based on patient instructions and clinical expectations, improvement in symptoms is generally expected to begin during the first few days of treatment.


Q: What are the signs of a serious, but rare, side effect of Infatrim?

Official labeling documents signs of serious, rare adverse reactions that require immediate attention. These include skin reactions such as blistering, peeling, or loosening of the skin (Severe Cutaneous Adverse Reactions), sore throat, fever, and signs of blood system toxicity like pallor or unusual bleeding.


Q: Can I use Infatrim if I have a history of liver issues?

Official documentation lists severe hepatic damage as an absolute contraindication for use. All patients with a history of liver issues require specific monitoring and evaluation before and during the course of treatment.

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How should Infatrim be stored and disposed of?

How to Store and Dispose of Infatrim?

The storage and disposal of Infatrim (sulfamethoxazole and trimethoprim) are governed by specific regulatory standards to maintain the product’s quality and ensure safety.

Storage Conditions

Infatrim tablets and suspension must be stored at Controlled Room Temperature, which is defined as 20 C to 25 C (68 F to 77 F). Brief temperature excursions up to 30 C (86 F) are permitted.

Formulation Constraint Requirement
Oral Suspension Must be protected from freezing and light
Container Rule Keep the container tightly closed and store in the original container
Safety Rule Must be kept out of the reach of children

Disposal Instructions

Any unused or expired product must be disposed of according to local regulations for pharmaceutical waste.

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

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