Polymyxin B Sulfate And Trimethoprim
What Is Polymyxin B Sulfate And Trimethoprim?
Polymyxin B Sulfate and Trimethoprim API is a combination antibiotic medication primarily used in ophthalmic (eye) formulations.
This dual-active-ingredient drug targets bacterial infections through a synergistic mechanism:
Polymyxin B Sulfate: A polypeptide antibiotic derived from Bacillus polymyxa, it disrupts bacterial cell membranes by binding to lipopolysaccharides (LPS) in Gram-negative bacteria, leading to cell lysis.
Trimethoprim: A dihydrofolate reductase inhibitor, it blocks folate synthesis in bacteria, effectively halting DNA replication. This component primarily targets Gram-positive bacteria.
The FDA approved this combination in 1988 under Polytrim and later in 1997 as a generic formulation.
It is available as a sterile ophthalmic solution (10,000 units/mL Polymyxin B Sulfate and 1 mg/mL Trimethoprim).
Its unique formulation ensures broad-spectrum coverage against common ocular pathogens.
Polymyxin B Sulfate Introductions
Polymyxin B is a polypeptide antibiotic primarily used against Gram-negative bacteria.
These bacteria are notoriously difficult to treat due to their resistance.
Polymyxin B sulfate is a white to off-white powder with Cas No. 1405-20-5.
Discovered in the late 1940s, it has become valuable in treating infections caused by certain multi-drug-resistant organisms.
Polymyxin B is often administered topically as an ointment or spray with zinc bacitracin and neomycin, but it can also be given intravenously (made into injections) for systemic infections.
Polymyxin B Sulfate Main Uses
1. Topical Infections
Effective against numerous Gram-negative bacteria, it is often part of topical formulations for treating skin infections.
2. Systemic Infections
In severe infections caused by resistant Gram-negative bacteria, Polymyxin B can be administered intravenously, especially in healthcare settings.
3. Ocular Infections
People also use it in eye drops for bacterial conjunctivitis and other ocular infections.
4. Infections in Patients with Compromised Immune Systems
Researchers also try polymyxin B to treat immunocompromised patients at risk for infections caused by resistant bacterial strains.
Trimethoprim Introductions
Trimethoprim is an antibiotic that acts as a folate synthesis inhibitor.
It works by blocking dihydrofolate reductase, an enzyme essential for bacterial growth.
This intervention prevents the bacteria from synthesizing DNA and RNA, ultimately inhibiting their growth and reproduction.
Trimethoprim is often used alone or in combination with sulfamethoxazole, which enhances its efficacy against a broader array of infections.
Trimethoprim Main Uses
1. Urinary Tract Infections (UTIs)
Doctors prescribe Trimethoprim for uncomplicated UTIs caused by susceptible organisms like Escherichia coli.
2. Respiratory Infections
It can be effective against specific respiratory pathogens, making it helpful in treating bronchitis or pneumonia.
3. Gastrointestinal Infections
Doctors also use Trimethoprim to treat some gastrointestinal infections, particularly those caused by Shigella and Salmonella.
4. Skin Infections
It is used for skin and soft tissue infections, mainly caused by sensitive bacteria.
5. Prophylaxis
In some cases, people use Trimethoprim as prophylaxis against opportunistic infections in patients with compromised immune systems, such as those with HIV/AIDS.
What Is Polymyxin B Sulfate And Trimethoprim Used For When Combined?
This antibiotic combination is prescribed for bacterial eye infections, including:
Conjunctivitis (Pink Eye): Treats infections caused by Staphylococcus aureus, Streptococcus pneumoniae, and Haemophilus influenzae.
Blepharitis: Addresses eyelid inflammation linked to bacterial overgrowth.
Keratitis: Used for corneal infections, particularly those resistant to single-antibiotic therapies.
Its efficacy against multidrug-resistant (MDR) Gram-negative bacteria like Pseudomonas aeruginosa and Acinetobacter baumannii makes it critical in ophthalmology.
The dual-action mechanism reduces the risk of resistance development compared to monotherapies.
Mechanism of Action: How Does This Combination Work?
The synergy between Polymyxin B and Trimethoprim ensures comprehensive bacterial eradication:
Polymyxin B Sulfate:
It targets the outer membrane of Gram-negative bacteria by binding to LPS, creating pores that leak cellular contents 5.
It does not require entry into the cell, making it effective against pathogens with thick extracellular matrices.
Trimethoprim:
It inhibits dihydrofolate reductase, an enzyme critical for folate synthesis.
Starves bacteria of thymidine and purines, preventing DNA/RNA production.
This combination covers both Gram-positive and Gram-negative bacteria, addressing polymicrobial infections effectively.
Clinical Efficacy and Research Insights
FDA Approval and Historical Data
Polytrim: First approved in 1988 (NDA 050567) by Allergan Inc. as a reference-listed drug.
Generic Version: Approved in 1997 (NDA 064120) by Bausch & Lomb, with multiple post-approval revisions to optimize microbiology and labeling.
Analytical Validation
Recent studies highlight advanced methods for quantifying Polymyxin B in formulations.
A 2024 green spectrophotometric assay using Erythrosine B dye demonstrated precise Polymyxin B and Trimethoprim measurement in parenteral and ophthalmic solutions, ensuring drug quality and consistency.
Dosage and Administration Guidelines
Form: Ophthalmic solution (sterile drops).
Dosage:
Adults and Children: 1–2 drops every 3–4 hours, depending on severity.
Maximum Duration: 7–10 days to avoid resistance.
Storage: Keep at room temperature (15–25°C); avoid contamination by not touching the dropper tip to the eye.
Safety Profile and Side Effects
While generally well-tolerated, potential side effects include:
Common: Temporary stinging, blurred vision, or redness.
Rare: Allergic reactions (itching, swelling).
Contraindications include hypersensitivity to either component.
Long-term use may predispose patients to fungal superinfections.
Comparison with Other Antibiotics
| Features | Polymyxin B/Trimethoprim | Fluoroquinolones (e.g., Ciprofloxacin HCl) | Aminoglycosides (e.g., Gentamicin Sulfate) |
|---|---|---|---|
| Spectrum | Broad (Gram +/-) | Broad | Narrow (Gram -) |
| Resistance Risk | Low | Moderate-High | Moderate |
| Administration | Topical | Topical/Oral/IV | Topical/IV |
This combination’s low resistance risk and topical application make it preferable for localized eye infections.
Does Polymyxin B Sulfate and Trimethoprim Expire?
Yes, it does.
When medicine manufacturers make polymyxin b sulfate and trimethoprim into eye drops or solutions, they have an expiry date; even when appropriately stored in a refrigerator, they will still expire.
The shelf life is around 1~3 years.
It also has something to do with the storage conditions.
If the eye drops are not opened and stored correctly, they will be effective with stated efficacy.
There are two types of eye drops: the multiuse type containing preservatives and the preservative-free single-use type.
Once opened, try to use the standard type with preservatives within a month and a day for single-dose type, or discard it.
So, stop using eye drops that are past their expiration date or opened solutions older than a month (24 hours for the single-use type) to avoid possible dangers.
Expired eye drops can worsen eye infections. Why? Once you open the eye drop, it quickly gets contaminated.
The active ingredients and excipients can break down into something you don’t want to get into your eyes.
Patient FAQs
Can I Use This for Viral Conjunctivitis?
No, it is ineffective against viral or fungal infections. Misuse can exacerbate antibiotic resistance.
Is It Safe During Pregnancy?
Consult a healthcare provider. Animal studies show no teratogenicity, but human data are limited.
Disclaimer:
This content is for informational purposes only and is intended for business-to-business communication within the pharmaceutical industry. It is not intended as medical advice. The manufacture, import, and use of API must comply with all applicable laws and regulations in the relevant country or region.
This blog post is informational only and does not constitute medical advice.
Always consult a healthcare professional before starting any new medication or treatment.
