Bactricid

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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 Bactricid

Property Description
Active Ingredients Sulphamethoxazole and Trimethoprim
Form Tablet, Oral Suspension, IV Solution
Pharmacological Class Systemic Anti-infective Agent (Antibacterial Combination Product)
Common Use Treating bacterial infections
Origin Synthetic

What is Co-trimoxazole and What Class Does it Belong To?

Bactricid is a widely recognized trade name for the generic medicine Co-trimoxazole, which is a synthetic fixed-dose combination product classified as a systemic anti-infective agent. This drug belongs to the broader antibacterial combination product class, established for the general purpose of eliminating bacterial growth throughout the body. Co-trimoxazole is included on the Model List of Essential Medicines, reflecting its role in public health as a medicine recognized as effective and necessary for meeting core health needs. Other popular brand names utilizing this identical formulation include Bactrim and Septra.


Composition: The Combination of Sulphamethoxazole and Trimethoprim

The medicine's composition features two primary active ingredients: Sulphamethoxazole (SMX) and Trimethoprim (TMP). Sulphamethoxazole is chemically a sulfonamide antibiotic, while Trimethoprim is categorized as a dihydrofolate reductase inhibitor. This combination is often utilized in a Double Strength (DS) tablet formulation. The dual active composition ensures that the medicine can be formulated into various high-level dosage forms, including the oral tablet, oral suspension (liquid) suitable for pediatric patients, and a solution for intravenous infusion. This versatility in forms, supporting both oral and intravenous routes of administration, ensures the medicine can be delivered effectively based on patient need.


The Unique Principle of Dual Blockade and Synergism

The medicine's unique effectiveness stems from a synergistic effect achieved through a principle known as dual blockade, which is crucial to its general purpose. This means the two ingredients work together to actively disrupt two consecutive, essential steps in the bacterial survival process, resulting in a bactericidal (bacteria-killing) action. This specific two-pronged strategy targets the bacterial folate synthesis pathway. The dihydrofolate reductase inhibition provided by Trimethoprim is the second step in this pathway, a key differentiating feature. This strategy makes it more difficult for bacteria to develop resistance to the treatment, resulting in a decisive therapeutic outcome compared to many single-drug treatments.

Regulatory References

  1. World Health Organization Model List of Essential Medicines
  2. Co-trimoxazole on WHO Essential Medicines List

What side effects are possible with Bactricid?

Possible Side Effects and Safety Information

The official safety profile for Co-trimoxazole (Bactricid) systematically details adverse reactions based on frequency and affected body systems, as established by regulatory authorities like the EMA and FDA. Side effects are classified from Very Common to Very Rare, reflecting data documented in official prescribing information.

Commonly Documented Adverse Reactions

Adverse reactions classified as Common (affecting up to 1 in 10 people) typically include nausea, diarrhea, headache, and rash. A Very Common finding (affecting more than 1 in 10 people) is hyperkalemia (elevated potassium levels), which falls under the Metabolism and Nutrition Disorders System-Organ Class.


Serious Adverse Reactions and Safety Constraints

The medicine is associated with documented Very Rare but serious reactions. These include severe cutaneous adverse reactions (SCARs), such as Stevens-Johnson syndrome (SJS) and Toxic Epidermal Necrolysis (TEN), and significant blood disorders, including agranulocytosis and aplastic anemia. The highest risk for these severe skin reactions is generally observed during the first weeks of treatment.

Population-Specific and Usage Restrictions

Regulatory documents outline specific safety constraints. The medicine is contraindicated in infants under two months of age, patients with severe hepatic damage, and individuals with documented megaloblastic anemia due to folate deficiency. Elderly patients are noted to have increased susceptibility to adverse effects, particularly the risk of thrombocytopenia (low platelets) when concurrently using certain diuretics. For all patients, maintaining adequate urinary output is necessary to mitigate the rare risk of crystalluria.

Overdose and Emergency Response

Overdose and When to Seek Help

Official regulatory documents define the overdose profile of Co-trimoxazole (Bactricid) through documented acute symptoms, severe systemic toxicities, and mandated emergency response actions. No specific antidote is known for the acute toxicity of the combination product; therefore, management relies primarily on supportive measures.

Overdose may present acutely with symptoms such as nausea, vomiting, dizziness, anorexia, confusion, and ataxia. Severe, life-threatening outcomes documented in the context of high-dose or chronic overdose include fulminant hepatic necrosis, aplastic anaemia, severe allergic reactions like Stevens-Johnson syndrome (SJS), and severe metabolic imbalances like hyperkalaemia.

Mandatory Emergency Actions

Overdose Presentation Regulator-Mandated Action
Any suspected overdose Seek immediate medical attention or contact a Poison Control Helpline.
Collapse, seizure, trouble breathing, or inability to be awakened Immediately call emergency services (911).

Supportive Management

Treatment procedures documented in official labeling include symptomatic and supportive measures, possible administration of activated charcoal, and maintaining adequate urinary output to minimize crystalluria risk. Folinic acid supplementation may be required to counteract haematological effects resulting from chronic high-dose exposure. The elderly population is cited as more susceptible to serious toxic effects, particularly with impaired kidney or liver function.

Therapeutic Uses of Bactricid

What Bactricid Treats: Main Uses and Benefits

Bactricid is applied in contexts where additional symptomatic support is needed for conditions associated with acute or episodic changes, often used during phases when symptoms become more noticeable. It is relevant across domains involving heightened systemic burden, including certain types of pneumonia and traveler's diarrhea. This includes addressing conditions involving episodic or fluctuating manifestations, such as Urinary Tract Infections (UTIs), acute exacerbations of chronic lung disease (AECB), specific severe gastrointestinal conditions like Shigellosis, and certain Skin and Soft Tissue Infections (SSTIs).


Quick Fact: Relief for Acute Discomfort

Quick Fact: Relief for Acute Discomfort Bactricid is applied in clinical settings that involve acute or unstable symptom patterns or when symptoms related to UTIs and acute bronchitis create noticeable physiological strain.


This supportive strategy is relevant for conditions characterized by periods of heightened symptoms, such as Pneumocystis Jirovecii Pneumonia (PJP), where it helps maintain a sense of stability when symptoms are more noticeable, supporting the patient during difficult episodes by easing distress. The core therapeutic benefit is used across domains where additional symptomatic support is needed, assisting with maintaining functional stability.

“The primary goal is to provide supportive relief when symptoms interfere with routine activities, contributing to a more manageable symptomatic period.”

Regulatory References

  1. NIH MedlinePlus Drug Information

Eligibility and Restrictions for Use

Bactricid (a combination of sulfamethoxazole and trimethoprim) is an antibiotic used to treat various bacterial infections. Its use is determined by the specific infection and a patient's medical history.


Who Can Use Bactricid?

Generally, Bactricid may be prescribed for individuals with infections caused by susceptible bacteria, such as certain urinary tract infections (UTIs), some types of pneumonia (Pneumocystis pneumonia, or PCP), acute otitis media in children, and traveler's diarrhea. Prescription is typically dependent on the organism's sensitivity to the drug and the patient’s overall health profile.


Contraindications (Who Should Not Use Bactricid)

Bactricid is contraindicated in several groups to prevent serious adverse effects. Do not use Bactricid if you have a known allergy to sulfonamides (sulfa drugs) or trimethoprim.

It is also generally avoided in patients with:**

  • Significant liver damage (hepatotoxicity)
  • Severe kidney impairment (unless undergoing close monitoring)
  • A history of drug-induced immune thrombocytopenia (a low platelet count caused by the drug)
  • Megaloblastic anemia due to folate deficiency.

Bactricid is also typically not used in infants less than two months old due to the risk of kernicterus (a type of brain damage caused by high bilirubin levels).

What should I know about interactions with other medicines?

Bactricid (sulfamethoxazole and trimethoprim) can interact with a wide range of other medicines, potentially altering their effects or increasing the risk of adverse reactions. These interactions often occur due to the medicine's effect on drug metabolism (through CYP enzymes) or renal transport mechanisms (such as OCT2).

Key interactions include:

  • Dofetilide: Coadministration is contraindicated due to the risk of life-threatening heart rhythm issues.
  • Blood Thinners (e.g., Warfarin): Bactricid can increase the blood-thinning effect, requiring frequent monitoring of coagulation tests (INR/Prothrombin Time) to prevent bleeding.
  • Diabetes Medicines (e.g., Metformin, Glipizide, Pioglitazone): The combination may enhance the blood sugar-lowering effect, increasing the risk of hypoglycemia (low blood sugar).
  • Potassium-Raising Medicines (e.g., ACE Inhibitors, ARBs, Potassium-Sparing Diuretics): Concurrent use can cause hyperkalemia (elevated potassium levels), which can affect heart function, necessitating close serum potassium monitoring.
  • Digoxin: Increased blood levels of Digoxin can occur, particularly in older individuals, requiring monitoring of serum Digoxin concentrations.
  • Phenytoin and Methotrexate: Bactricid can increase the concentration of these medicines in the blood, raising the risk of toxicity and side effects. Avoidance of coadministration or dose adjustment may be necessary.
  • Cyclosporine: There have been reports of reversible kidney toxicity in transplant recipients when this combination is used.

Mechanism of Action

How Bactricid Works: Sequential Metabolic Blockade

Bactricid (Co-trimoxazole) is an antibacterial agent whose mechanism of action involves the dual sequential blockade of the bacterial metabolic pathway responsible for synthesizing active folate cofactors. The combination targets two consecutive enzymes. Sulphamethoxazole (SMX) acts first, competitively inhibiting Dihydropteroate synthase (DHPS). Subsequently, Trimethoprim (TMP) inhibits Dihydrofolate reductase (DHFR). By blocking both steps, the drug critically impairs the internal production of tetrahydrofolic acid (THF) within the microbial cell. The simultaneous action on two parts of the same pathway results in a synergistic effect; the combined inhibition exceeds the simple sum of the individual inhibitory actions. The profound depletion of THF subsequently arrests bacterial macromolecular synthesis, as THF is essential for creating the purine and thymidine bases required for DNA and RNA. This cascade leads directly to a bactericidal (bacteria-killing) physiological consequence, which results in the destruction of the targeted pathogen population. The mechanism exhibits selective toxicity due to the drug's differential affinity for bacterial DHFR compared to the human version, and the host cell's reliance on pre-formed folate. The functional range of the mechanism is constrained by bacterial mutations or the ability to utilize exogenous folate from the environment.

Dosage and Administration Information

The medicine Bactricid, which contains the active ingredients Sulfamethoxazole and Trimethoprim, is administered through two primary routes: orally, via tablets or oral suspension, or by slow intravenous (IV) infusion for severe infections. Administration via intramuscular injection or rapid IV injection is not authorized.

Usage is standardized into frequency patterns based on the clinical scenario. For standard acute infections, the typical dose (e.g., 160 mg Trimethoprim / 800 mg Sulfamethoxazole) is taken every 12 hours. Conversely, treatment for severe conditions, such as Pneumocystis Jirovecii Pneumonia (PJP), requires a higher total daily dose that is administered in divided amounts every 6 to 8 hours. The total course duration ranges from 5 days for certain gastrointestinal issues to 14 to 21 days for more severe infections.

Specific procedural rules govern the proper intake and delivery of the medicine. Oral dosing must be accompanied by adequate fluid intake to prevent crystallization in the urine. For the IV route, the concentrate requires mandatory dilution prior to use, commonly in 5 percent Dextrose in Water (D5W), and the resulting solution must be infused slowly over a period of 60 to 90 minutes. Dosing requires adjustment for specific populations: it is reduced by 50 percent for adults with moderate renal impairment (Creatinine Clearance 15 to 30 mL/min), and use is not recommended for infants under 2 months of age.

Recent Clinical Evidence

Research evidence / Overview of studies for Bactricid (Co-trimoxazole)

This overview summarizes the official clinical research and study landscape for Bactricid (Co-trimoxazole), focusing on what major governmental and peer-reviewed sources report without offering any individual medical advice or treatment instructions. The evidence described below reflects findings from studies conducted under specific research conditions.


Research Evidence for Urinary Tract Infections (UTIs)

Bactricid was studied for the treatment of acute, uncomplicated Urinary Tract Infections (UTIs), which are conditions often characterized by functional limitations and irritative states. The primary evidence base includes short-term Randomized Controlled Trials (RCTs) and comparative clinical studies that research examined in adult women, as well as some pediatric patient populations.

The studies monitored outcomes related to physical discomfort and systemic imbalance, specifically measuring microbiological eradication (the clearing of bacteria from the urine) and the evolution of acute symptoms. The findings report patterns related to the clearance of common UTI-causing bacteria, such as E. coli, following the treatment course.

However, the certainty regarding its use remains low in many regions due to the increasing frequency of bacterial resistance reported in many geographic areas. Older research may not fully reflect current resistance patterns.


Research Evidence for Pneumocystis Jirovecii Pneumonia (PJP)

Bactricid was evaluated in extensive studies for both the treatment and prophylaxis (prevention) of Pneumocystis Jirovecii Pneumonia (PJP), which was studied in clinical research involving periods of heightened symptoms. The evidence base is considered substantial, comprising large-scale RCTs, systematic reviews, and long-term observational cohort studies. This research was chiefly conducted in immunosuppressed adults and children, particularly those with HIV infection.

The studies explored major outcomes such as all-cause mortality (death rate) and the incidence of PJP (occurrence) in at-risk groups. Long-term observational studies described patterns related to the prevention of PJP occurrence over extended periods in high-risk patients. These findings contribute to the understanding of the medicine in this specific patient population.


Key Research Gaps and Areas of Uncertainty

Research highlights that evidence quality varies across studies, particularly when examining the use of the medicine for less severe or niche conditions. One significant area of uncertainty is the widespread emergence of antimicrobial resistance to both Sulphamethoxazole and Trimethoprim. Because many foundational trials are older, the research is ongoing to understand how resistance patterns affect the current measured response of the medicine in clinical practice globally.

Furthermore, while studies describe group patterns, the evidence does not determine whether an individual will respond similarly. Comparative evidence is lacking for many niche uses, and follow-up durations were limited for most acute indications. This means that research provides context but not individual predictions regarding long-term outcomes or personal response.

Key Studies & References

  1. Pneumocystis Pneumonia: Adult and Adolescent Opportunistic Infection Guidelines | NIH - Clinical Info .HIV.gov
  2. Low-dose trimethoprim-sulfamethoxazole treatment for Pneumocystis pneumonia: a systematic review and meta-analysis

Frequently Asked Questions (FAQ)

Common questions about Bactricid (FAQ)

Q: What should I do if I miss a dose of Bactricid?

Official patient information states that if a dose is missed, it is typically advised to take it as soon as it is remembered. However, if it is nearly time for the next scheduled dose, the general guidance is to skip the missed dose entirely. A double dose should generally not be taken to compensate for a missed dose.


Q: Is a metallic taste in the mouth a common side effect of Bactricid?

Taste disturbances, including experiencing a metallic or bitter taste, have been reported as an adverse effect in the medicine's official safety profile. If this or any side effect is concerning, contacting a healthcare professional for guidance is recommended.


Q: Why does Bactricid sometimes cause sun sensitivity?

Regulatory documents indicate that this medicine can cause photosensitivity, which is an increased sensitivity to sunlight. This effect is generally linked to the sulphonamide component of the drug. Due to this risk, the label advises protective measures, such as avoiding unnecessary sun exposure and using protective clothing.


Q: Is it safe to drink alcohol in moderation while taking Bactricid?

Official patient information often suggests discussing alcohol consumption with a healthcare provider while using this medicine. Some patient safety advice highlights that combining the medicine with alcohol may cause adverse effects like flushing, rapid heart rate, and gastrointestinal upset.


Q: How long after finishing the full course of Bactricid will it remain in my system?

According to the official pharmacokinetics data, the active ingredients have mean half-lives ranging from approximately 8 to 10 hours in adults with normal kidney function. This means that detectable amounts of the medicine may remain in the bloodstream for several days after the final dose.


Q: Is Bactricid safe to use during pregnancy (in general terms)?

Regulatory documents suggest that using the medicine during pregnancy may be associated with an increased risk of congenital malformations, particularly neural tube defects. Official patient guidance emphasizes that potential hazards to the fetus should be communicated if the medicine is used during pregnancy. It is generally only considered if the potential benefit outweighs the potential risk.


Q: Is Bactricid appropriate for use in children?

Official regulatory approval is given for the use of Bactricid in children 2 months of age and older for specific infections. However, the medicine is strictly contraindicated and must not be used in infants younger than 2 months due to safety risks.


Q: Are there any specific foods or drinks that should be avoided when taking Bactricid?

The official label does not mandate avoiding specific common foods. However, because Bactricid is associated with a risk of hyperkalemia (elevated potassium levels), a cautious approach to high-potassium foods or supplements is generally suggested, especially for individuals using other potassium-raising medications.


Q: Is it normal to feel slightly dizzy or lightheaded after taking Bactricid?

Dizziness is officially listed as a common adverse reaction in the drug's safety profile. Additionally, lightheadedness or confusion may be a symptom of adverse changes in blood electrolytes, such as low blood sodium or high potassium, which are also reported side effects of the medicine.


Q: What are the signs of a severe skin reaction (like Stevens-Johnson Syndrome) linked to Bactricid?

Regulatory warnings state that signs that could signal a Severe Cutaneous Adverse Reaction (SCAR), such as Stevens-Johnson Syndrome, should be reported promptly to a healthcare provider. These signs may include a high fever, severe headache, a rash, sore throat, or conjunctivitis (red eye).


Q: Does Bactricid have a warning about kidney stones or kidney problems?

The label notes the risk of crystalluria, which is the formation of crystals in the urine, and potentially kidney stone formation if a patient does not drink adequate fluids. Additionally, reports of impaired kidney function and renal failure are included as adverse effects in the official safety data.


Q: What is the risk of a yeast infection (thrush) after taking Bactricid?

As with many antibiotics, the risk of fungal overgrowth, such as candidiasis (commonly known as thrush or a yeast infection), is a reported adverse effect. This occurs because the medicine can eliminate the normal, beneficial bacterial flora in the body.


Q: Why do some people experience nausea or stomach upset with Bactricid?

Nausea, vomiting, and diarrhea are documented as common side effects in the medicine’s official safety information. These symptoms are generally considered to be the result of direct irritation to the gastrointestinal system and the necessary disruption of the normal gut bacteria.


Q: Can Bactricid be used for ear infections?

Yes, regulatory authorities have indicated the medicine for the treatment of acute otitis media (middle ear infection) in pediatric patients. This use is specific to infections caused by certain susceptible strains of Streptococcus pneumoniae or Haemophilus influenzae.


Q: Are there any long-term side effects associated with repeated courses of Bactricid?

Official guidelines indicate that regular monitoring is typically necessary for patients undergoing long-term treatment, or repeated courses. This typically includes blood counts, as well as kidney and liver function tests, due to the risk of hematological changes.


Q: What happens if Bactricid is taken past its expiration date?

Official storage and disposal guidelines indicate that the quality and full potency of the medicine are only guaranteed up to the expiration date printed on the packaging. Unused or expired medication should be safely disposed of according to local regulatory programs.


Q: Can Bactricid be used for traveler's diarrhea?

Yes, regulatory documents list the medicine as being indicated for the treatment of Traveler's Diarrhea in adults. This is specifically for cases caused by susceptible strains of the bacteria Escherichia coli.


Q: Is a headache a common side effect when starting Bactricid?

Headache is officially listed as a common adverse reaction in the drug's safety profile. While the timing of side effect onset is not always detailed, common adverse reactions often begin to manifest when a patient first starts taking the medicine.


Q: Does Bactricid cause insomnia or affect sleep patterns?

Yes, official reports indicate that insomnia, or difficulty sleeping, is a reported adverse effect that can be associated with taking this medicine.


Q: What is the connection between Bactricid and folic acid?

Bactricid works by blocking the synthesis of tetrahydrofolic acid, which is a type of folate, within bacteria. Because of this mechanism, the medicine is strictly avoided in patients who have a specific type of blood disorder called megaloblastic anemia that is caused by folate deficiency.


Q: Is there a liquid suspension form of Bactricid for people who can't swallow pills?

Yes, official dosage forms include an oral suspension (liquid form) of the medicine. This form is typically used for pediatric patients but may also be prescribed for people who have difficulty swallowing tablets.

How should Bactricid be stored and disposed of?

Storage and Disposal Requirements for Bactrim (Co-trimoxazole)

Official Storage Conditions

Bactrim (sulfamethoxazole and trimethoprim) must be stored at Controlled Room Temperature to maintain potency, with specific ranges varying by form. The tablets generally require storage between 15 C and 30 C. The medicine must be protected from light and moisture and should not be frozen. The product should always be kept in its original container.

Stability and Child Safety

For the oral suspension form, a stability constraint applies: the product must be discarded if unused 28 days after first opening. All forms of the medicine must be strictly kept out of the sight and reach of children.

Disposal Instructions

Unused or expired Bactrim must be disposed of according to local regulations. Government authorities recommend utilizing a community drug take-back program or following specific household disposal instructions, which typically advise against flushing the medicine down a toilet.

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

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