Urisept

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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.

Overview of Urisept

Urisept is the trade name for a synthetic pharmaceutical product known generically as Co-trimoxazole, which is an Antimicrobial Agent. This medication is specifically designed as a fixed-dose combination product containing two active substances used for the systemic treatment of bacterial infections. Co-trimoxazole is recognized for its efficacy.

Property Description
Active Ingredient Sulfamethoxazole and Trimethoprim
Form Tablet, Oral Suspension, Solution for Injection
Pharmacological Class Combination Antimicrobial Agent (Antibiotic)
Common Use Treatment of Bacterial Infections
Origin Synthetic

1. What Type of Medicine is Urisept?

Urisept is classified as an Antibiotic belonging to the pharmacological subgroup of combination antibacterials, which pairs a sulfonamide with a dihydrofolate reductase inhibitor. This formulation is often recognized under other established brand names such as Septra or Bactrim, reflecting its clinical use and history. The dual-component approach is included on the World Health Organization (WHO) Model List of Essential Medicines.

2. Composition and Available Forms of Urisept

The product's composition is defined by its two primary active ingredients: Sulfamethoxazole and Trimethoprim. This pairing is central to the drug’s action. The medication is manufactured in several dosage forms for systemic administration. This includes the Tablet and Oral Suspension (a liquid form, often used for pediatric patients), as well as a sterile Solution for Injection for intravenous use in acute settings.

3. How Urisept’s Dual Action Provides General Benefit

The general therapeutic purpose of Urisept is achieved through a synergistic process of sequential blockade in combating bacteria. The combined agents block two consecutive steps in the bacteria’s ability to produce necessary growth compounds (folic acid), resulting in a bactericidal effect. The synergistic effect of the combination is utilized for treating a variety of bacterial pathogens, such as those encountered in respiratory or urinary tract infections.

Regulatory References

  1. Trimethoprim Sulfamethoxazole - StatPearls
  2. Co-trimoxazole on WHO Essential Medicines List
  3. Sulfamethoxazole and Trimethoprim Injection - DailyMed
  4. Trimethoprim Sulfamethoxazole - StatPearls (Mechanism of Action)

What side effects are possible with Urisept?

Possible side effects and safety information

The safety profile of Co-trimoxazole (Urisept) is categorized by regulatory authorities based on the frequency and the physiological systems affected. These classifications communicate the officially documented risks associated with the medicine.

Adverse Reaction Classification

Adverse reactions are organized into System-Organ Classes (SOCs) including Blood and Lymphatic System Disorders, Gastrointestinal Disorders (e.g., nausea, diarrhoea), Nervous System Disorders (e.g., headache), and Skin and Subcutaneous Tissue Disorders (e.g., rash).

Frequency Classification Examples of Documented Effects
Very Common (ge 1/10) Hyperkalemia (high blood potassium)
Common (ge 1/100 to <1/10) Headache, nausea, diarrhoea, fungal overgrowth, rash
Very Rare (<1/10,000) Blood disorders (e.g., Agranulocytosis), Severe Skin Reactions (SJS, TEN)

Documented Serious Adverse Reactions and Constraints

Regulatory documents explicitly list rare but serious events, including severe blood dyscrasias like Aplastic Anemia and potentially fatal fulminant hepatic necrosis (severe liver damage). Life-threatening severe cutaneous reactions (SCARs) such as Stevens-Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN) have been officially documented. The highest risk for the occurrence of SCARs is officially noted to be within the first weeks of treatment.

Specific Population-Specific Safety Considerations apply. The medicine is contraindicated for infants younger than two months of age. Furthermore, an increased risk for certain adverse reactions, such as thrombocytopenia (low platelet count), is noted for older adults, especially when concurrent diuretic use is present. Contraindications also apply to individuals with severe hepatic or renal impairment.

Overdose and Emergency Response

Overdose and when to seek help

Suspected overdose with Urisept (Co-trimoxazole) requires an immediate response as documented in regulatory information. Acute overdose may present with central nervous system effects such as drowsiness, confusion, headache, dizziness, and mental depression. Gastrointestinal symptoms commonly include nausea, vomiting, and anorexia.


Severe Outcomes and Emergency Action

Regulators mandate that individuals seek immediate medical attention for any known or suspected overdose. Emergency services (911) must be called immediately if the person exhibits collapse, seizure, trouble breathing, or cannot be awakened. The Poison Control Helpline should also be contacted.

Severe overdose carries a risk of serious outcomes, including life-threatening hyperkalemia, renal failure, and delayed hematologic toxicity (blood disorders). Elderly patients and those with severely impaired renal function are noted to be more susceptible to serious adverse effects in this context.

Management is defined as symptomatic and supportive treatment. Procedural steps officially documented in regulatory labeling include gastric lavage or activated charcoal administration, and monitoring for electrolyte imbalances and bone marrow depression. Folinic acid is specified for treating the hematologic toxicity component of the overdose.

Therapeutic Uses of Urisept

Primary Therapeutic Indications

Urisept is a combination medication primarily utilized for the management of inflammatory and infectious conditions affecting the lower urinary tract. It is most commonly employed to address symptoms associated with acute and chronic cystitis, which is the inflammation of the bladder. The medication is formulated to target the discomfort arising from irritations of the urinary mucosa.

Mechanisms of Action

The efficacy of the medication is derived from its multi-component approach to urinary tract health:

  • Antiseptic Action: It contains agents that help inhibit the growth of bacteria within the urine and along the urinary tract walls, assisting the body in clearing localized infections.
  • Acidification: Certain components work to acidify the urine, creating an environment that is less hospitable to many common uropathogenic bacteria.
  • Symptomatic Relief: The formulation includes ingredients that provide a mild analgesic effect directly to the urinary tract lining, helping to reduce the burning sensation and urgency often associated with urinary infections.

Main Benefits in Clinical Use

When used as part of a comprehensive treatment plan for urinary conditions, the medication offers several clinical benefits:

Reduction of Discomfort

One of the primary benefits is the alleviation of dysuria (painful urination). By soothing the irritated lining of the bladder and urethra, it helps reduce the frequency of painful spasms.

Support of Urinary Hygiene

By exerting a continuous antiseptic effect as it is excreted through the kidneys, the medication helps maintain a cleaner urinary environment. This is particularly beneficial for individuals prone to recurrent irritations or those requiring supportive therapy alongside primary antibiotics.

Management of Chronic Irritation

In cases of chronic urinary tract sensitivity, the medication may be used to help manage low-grade, persistent symptoms that do not always require aggressive systemic antibiotic intervention but still impact daily comfort.

Eligibility and Restrictions for Use

Who Can and Cannot Use Urisept?

Urisept (Co-trimoxazole) eligibility is strictly defined by regulatory authorities based on patient population, age, and pre-existing medical conditions.


Contraindicated Populations (Must Not Use)

Category Prohibition
Hypersensitivity Known allergy to trimethoprim, sulfonamides, or any component.
Organ Function Severe impairment of liver function or severe renal insufficiency (Creatinine Clearance < 15 mL/min).
Hematological Status Documented megaloblastic anemia due to folate deficiency or a history of drug-induced immune thrombocytopenia.
Age/Reproductive Status Infants under 2 months of age; pregnant women at term/near delivery.

Populations Requiring Restricted or Conditional Use

Category Regulatory Requirement
Renal Impairment Moderate renal impairment (CrCl 15 -30 mL/min) requires a dose reduction.
Metabolic Conditions Patients with G-6-PD deficiency should use the medicine with caution due to the risk of hemolysis.
Older Adults Particular care is advised due to increased susceptibility to adverse reactions, especially with compromised liver or kidney function.

The medicine is generally approved for adults and children 2 months of age and older. Use during the first trimester of pregnancy and lactation requires careful consideration and is subject to official restrictions, particularly when the infant is premature or jaundiced.

What should I know about interactions with other medicines?

Urisept (Co-trimoxazole) has officially documented interaction patterns that may alter the plasma exposure or physiological effects of co-administered medicines.

Formal Regulatory Contraindications

Co-administration with Dofetilide is contraindicated due to the formal risk of significantly increased dofetilide plasma concentrations, which can lead to life-threatening ventricular arrhythmias. The combination with Methotrexate is also formally prohibited when methotrexate concentrations exceed a specific labeled threshold, as this enhances the risk of haematological toxicity.

Pharmacokinetic and Pharmacodynamic Interactions

The product is documented to inhibit the metabolic clearance of several medicines, including the anticoagulant Warfarin, the anticonvulsant Phenytoin, and certain Sulfonylureas. This inhibition can lead to an increase in the plasma concentrations of these agents, raising the risk of bleeding (Warfarin) or hypoglycemia (Sulfonylureas).

Furthermore, Urisept is known to inhibit specific renal and membrane transporters (P-gp and OCT2/MATE1). This mechanism increases the systemic exposure of co-administered agents such as Digoxin, Lamivudine, and Procainamide.

A major pharmacodynamic constraint exists with potassium-altering agents. Co-administration with Potassium-Sparing Diuretics (e.g., Spironolactone) carries a significant risk of severe hyperkalemia due to an additive effect on renal potassium excretion. This risk, along with the potential for thrombocytopenia when combined with Thiazide Diuretics, is formally noted to be heightened in elderly patients. Regulatory labels confirm that administration with food does not significantly affect the absorption of the active ingredients.

Mechanism of Action

Sequential Dual-Enzyme Blockade

The foundational mechanism of Urisept, a fixed-dose combination, involves the sequential inhibition of two crucial enzymes in the bacterial folic acid synthesis pathway: Dihydropteroate Synthase (DHPS) and Dihydrofolate Reductase (DHFR). Sulfamethoxazole acts as a competitive antagonist of PABA for DHPS, and Trimethoprim inhibits DHFR. This coordinated, two-step blockade prevents the bacteria from producing the necessary Tetrahydrofolic Acid (THF), a co-factor essential for bacterial cell viability.

Synergistic Cascade to Cell Death

By striking two consecutive points in the metabolic chain, the action of the components becomes synergistic, meaning the effect of the combination is significantly greater than the additive effect of the individual agents. This leads to the complete and rapid halt of DNA and RNA precursor synthesis, resulting in a bactericidal effect—the physiological process of actively destroying the bacterial organism.

Specificity and Mechanistic Constraints

The mechanism is highly specific to bacteria that must synthesize their own folate, contrasting with human cells that acquire it exogenously. However, the action is constrained against bacterial strains that have developed resistance through specific enzyme mutations or those that can bypass the blockade by utilizing preformed folate from the surrounding physiological environment.

Dosage and Administration Information

Urisept (Co-trimoxazole) is utilized through two distinct routes of administration: oral intake (as tablets or liquid suspension) and intravenous (IV) infusion. The specific route chosen depends on the clinical requirements of the treatment.

Adult therapy involves taking one 800 mg Sulfamethoxazole and 160 mg Trimethoprim Double Strength (DS) tablet per dose. The dosing frequency is typically maintained at every 12 hours. For the oral form, the medicine may be taken with or without food; however, it is administered with a full glass of water to ensure adequate fluid intake is maintained throughout the treatment course.

Intravenous use follows distinct preparation requirements. The solution for injection must first be diluted in 5% Dextrose in Water (D5W) and must not be mixed with other agents. Administration of this IV preparation must be slow, requiring an infusion period of 60 to 90 minutes, and rapid or bolus injection is prohibited.

There are also population-specific rules for use. For patients with impaired kidney function, a half-dose regimen is utilized if the creatinine clearance is between 15 and 30 mL/min. Furthermore, the medication is restricted from use in infants younger than two months of age.

Recent Clinical Evidence

Research Evidence / Overview of Studies for Urisept (Co-trimoxazole)


Evidence for Use in Systemic Bacterial Infections

The research landscape for Urisept's use as a combination antimicrobial agent includes Randomized Controlled Trials (RCTs) and comprehensive systematic reviews spanning decades. Research was studied for the purpose of exploring how symptoms change over time and for examining outcomes related to bacterial populations. Studies were evaluated in both adults and pediatric patients who had been diagnosed with various systemic bacterial infections, including those affecting the respiratory and gastrointestinal tracts.

The findings describe patterns observed in the studies related to measurements of microbiological clearance, which means the presence of the target bacteria was reduced in testing. The evidence contributes to the broader evidence landscape, which is used to contextualize the medicine’s inclusion on the World Health Organization’s list of essential medicines.

However, research so far indicates that while initial outcomes related to bacterial clearance were recorded in studies, a significant area of ongoing research examines the impact of the drug combination on the emergence of antimicrobial resistance over time, which may influence future performance against common pathogens.


Evidence for Use in Urinary Tract Infections (UTIs)

Urisept was studied for conditions characterized by fluctuating or episodic manifestations, specifically acute infections of the urinary tract. Research has explored the medicine’s outcomes in Comparative RCTs assessing different recognized treatment regimens, as well as in observational settings evaluating daily-life functioning. Studies monitored outcomes related to physical discomfort, which included measurements of patient-reported symptoms such as pain, burning, and urgency.

Trials described patterns of change in reported UTI symptoms and the rates of microbiological clearance from the urine samples tested. Findings were mixed when evaluating the medicine against certain newer drugs in trials; however, the data show patterns related to its long-established role in the study of these infections.

The certainty remains low regarding the full impact of geographic variability in bacterial susceptibility profiles, as resistance patterns can differ greatly between regions. Research is ongoing to better understand how data related to outcomes may evolve in the face of bacterial resistance.


Evidence for Use in Prophylaxis (Preventative Use)

Urisept was evaluated in research contexts involving fluctuating or unstable symptoms in severely immunocompromised patients, where the risk of specific life-threatening infections is high. These long-term observational cohort studies and specialized RCTs were conducted during periods of increased symptom activity. Studies monitored outcomes related to systemic or functional imbalance by measuring the time elapsed before a patient experienced a specific opportunistic infection.

Findings indicate that the preventative use of Urisept was observed in studies to have an association with a lower frequency of specific opportunistic infections in the high-risk patient groups. Research describes that the medicine was evaluated in observational studies that monitored outcomes related to daily activity in these vulnerable individuals.

However, the results apply only to the populations studied, which were often specialized groups such as HIV-infected patients and organ transplant recipients. Data for certain groups remain insufficient, and comparative evidence is lacking for some of the newer, alternative preventative therapies.

Key Studies & References

  1. WHO Model List of Essential Medicines
  2. Prevalence of co-trimoxazole resistance among HIV-infected individuals: a systematic review and meta-analysis
  3. Comparison of Co-trimoxazole and Cephalexin Efficacy in Preventing Urinary Tract Infection among Children
  4. An integrative review on treatment guidelines for complicated urinary tract infections

Frequently Asked Questions (FAQ)

Common questions about Urisept (FAQ)


Q: Does Urisept change the color of my urine?

Official safety documents, which list the possible side effects, do not typically describe a change in urine color as a documented or common adverse reaction to this medicine. If you notice any unusual changes in your urine color while using Urisept, consult with a healthcare professional.


Q: Can Urisept be used if I have diabetes?

Official documents describe that Urisept may interact with certain medicines commonly used to manage diabetes, such as Sulfonylureas or Metformin. This interaction is due to how Urisept affects the body’s processing of those other medicines. Official information suggests reviewing all current medications with a healthcare provider before treatment begins.


Q: What is the difference between Urisept and a standard painkiller?

Urisept is officially classified as a combination antimicrobial agent, which means it is an antibiotic used to treat systemic bacterial infections. This classification is distinct from the class of analgesics (painkillers), whose main function is to relieve pain without treating a bacterial cause.


Q: Why is Urisept sometimes given before certain medical procedures?

Official information indicates that the medicine is sometimes used for prophylaxis. Prophylaxis means treatment given to prevent specific opportunistic infections in patients considered to be at high risk, rather than treating an infection that is already established.


Q: If I stop taking Urisept, how long does it stay in my system?

Official clinical pharmacology information describes the half-life of one active component as being between 8 and 10 hours. Detectable amounts of the components may still be present in the blood up to 24 hours after the medicine is last used.


Q: Is it possible to have an allergic reaction to Urisept?

Yes. Official warnings note a known allergy to the components as a contraindication (a reason not to use the drug). Additionally, allergic skin reactions (such as a rash) are listed among the common adverse effects reported in official documents.


Q: Is it safe to crush or chew Urisept tablets?

Regulatory guidance for certain tablet forms states that the medicine should preferably be swallowed whole. Official instructions indicate that the tablets should not be chewed or crushed.


Q: What are the signs that Urisept might be causing a serious reaction?

Regulatory patient information describes signs of potentially serious reactions a person should be aware of. These can include fevers or flu-like symptoms accompanied by a rash, and skin changes such as redness, blistering, or peeling. If these signs appear, immediate medical attention is necessary.


Q: Does Urisept contain any gluten or common allergens?

While the main labels may not list all common food allergens, the solution for intravenous injection is specifically labeled as containing sodium metabisulfite. This compound may cause allergic reactions in susceptible people.


Q: Is Urisept considered a controlled substance?

The active ingredient combination in Urisept is not classified as a controlled substance under U.S. federal regulation. Controlled substances are drugs that are regulated due to potential for abuse or dependence.


Q: Is Urisept only used for infections?

No. In addition to treating established bacterial infections, official indications note that the medicine is also approved for prophylaxis (prevention). This preventative use is directed against certain opportunistic infections in individuals who are at high risk.


Q: Can I use Urisept if I have glaucoma?

Official warnings and precautions advise caution for patients with glaucoma (a group of eye conditions that damage the optic nerve). This is due to the rare, documented risk of serious ocular complications, including a specific condition called angle-closure glaucoma.


Q: What is the maximum number of days Urisept is typically used for?

Official dosing schedules for various conditions specify treatment courses that typically range from 10 to 14 days for acute infections. For other specific indications, the duration of use may be up to 14 to 21 days or potentially longer.


Q: Why is my doctor asking me about my allergies before prescribing Urisept?

Official regulatory documents list known hypersensitivity or allergy to the active components—trimethoprim, sulfonamides, or any other part of the medicine—as a contraindication. This means that if a person has a known allergy, the medicine is officially not to be used.


Q: Is it mandatory to finish the full course of Urisept if my symptoms improve?

Regulatory patient information advises patients to keep using the medicine for the full prescribed time of treatment, even if symptoms begin to improve or disappear quickly. This is to support the full clearing of the infection as intended by the prescribed duration.


Q: Can Urisept cause changes in skin color or eyes?

Patient information describing the signs of serious reactions mentions symptoms that include the yellowing of the skin or eyes (known as jaundice). This sign can indicate a potentially severe reaction.


Q: Does Urisept make me sensitive to sunlight?

Yes. Official warnings and precautions note that the medicine can make a person more sensitive to the sun (an effect known as photosensitivity). Regulatory documents advise that patients limit their exposure to direct sunlight and UV light.


Q: Do experts view Urisept as a standard treatment?

The active ingredient combination is included on the World Health Organization’s Model List of Essential Medicines. This designation is used to confirm its long-established role and importance in the overall treatment landscape.

How should Urisept be stored and disposed of?

How to Store and Dispose of Urisept

The storage and disposal of Urisept (Co-trimoxazole) must follow official regulatory requirements to ensure product stability and safety.

Storage Conditions

The medicine must be stored at controlled room temperature, typically 20 C to 25 C, and must not exceed 30 C. It is mandatory to keep the product in its original, tightly closed container and protect it from light and excess moisture. The intravenous injection solution is specifically labeled not to be refrigerated. All forms must be stored out of the sight and reach of children.

Disposal Instructions

Do not use the medicine after the expiration date on the package. Unused or expired Urisept must not be thrown away in household trash or disposed of via wastewater (flushing). Patients should consult a pharmacist or local waste management professional for the proper disposal of regulated medicinal waste, in accordance with local requirements.

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

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