Unveiling Neomycin: Best Uses, History, Dosage, Side Effects, and Top 5 Brands in Pakistan

Introduction

Neomycin is a broad-spectrum antibiotic in the aminoglycoside class, commonly used to treat bacterial infections. Discovered in the mid-20th century, neomycin has become an essential medication in both human and veterinary medicine. Its efficacy in treating various infections, particularly those caused by Gram-negative bacteria, makes it a valuable tool in the medical arsenal.

History

Neomycin was discovered in 1949 by a team of scientists at Rutgers University in New Jersey, USA. The team, led by Dr. Selman Waksman, isolated the antibiotic from the bacterium Streptomyces fradiae. Initially, It was used to treat tuberculosis, but its effectiveness against a broader range of bacterial infections soon made it a popular choice for various medical conditions.

Chemical Composition and Properties

It is derived from the bacterium Streptomyces fradiae. It consists of a mixture of three components: neomycin A, B, and C, with neomycin B (also known as framycetin) being the most active form. The chemical structure of neomycin includes multiple amino sugars attached to a 2-deoxystreptamine nucleus, which is characteristic of aminoglycosides.

Chemical Structure

The molecular formula of neomycin is C23H46N6O13, with a molecular weight of 614.64 g/mol. It is a highly polar molecule, which contributes to its poor absorption from the gastrointestinal tract when taken orally.

Mechanism of Action

Neomycin works by binding to the 30S ribosomal subunit of bacterial cells, inhibiting protein synthesis and ultimately leading to cell death. This mechanism of action makes it effective against a wide range of bacterial species, including E. coli, Staphylococcus aureus, and Klebsiella pneumonia.

DNA Binding

Uses of Neomycin

It is utilized in various forms for different medical applications. These include topical ointments, oral formulations, and combination products. Its use is primarily external due to its poor systemic absorption and potential for nephrotoxicity and cytotoxicity.

Topical Applications

Neomycin is frequently used in topical forms such as creams, ointments, and powders for external applications. It is effective against skin infections and is often included in combination with other antibiotics or corticosteroids.

1.1 Skin Infections

This medication is often used in topical creams, ointments, and powders to treat minor skin infections. It is effective against a variety of bacterial infections and is commonly included in over-the-counter first aid products to prevent infections in minor cuts, scrapes, and burns.

1.2 Eye Infections

Ophthalmic formulations of neomycin are used to treat bacterial infections of the eye, such as conjunctivitis and blepharitis. These preparations are usually combined with other antibiotics or steroids to enhance their effectiveness.

1.3 Ear Infections

It is used in otic (ear) solutions to treat bacterial infections of the outer ear (otitis externa). It helps to reduce inflammation and eliminate bacteria in the ear canal.

2. Oral Applications

Oral neomycin is less commonly used due to its potential toxicity but is effective in specific scenarios such as:

2.1 Bowel Preparation

Neomycin is administered orally as part of the preoperative preparation for bowel surgery. It helps to reduce the number of bacteria in the intestines, thus minimizing the risk of infection during surgery.

2.2 Hepatic Encephalopathy

In patients with hepatic encephalopathy, this drug is used to decrease the production of ammonia by intestinal bacteria. Lowering ammonia levels helps manage symptoms associated with this liver condition, such as confusion and neurological impairment.

3. Combination Therapy

Neomycin is often combined with other antibiotics or steroids to enhance its effectiveness and reduce inflammation.

3.1 Neosporin

Neomycin is a key ingredient in Neosporin, a popular topical antibiotic ointment. It is combined with polymyxin B and bacitracin to create a broad-spectrum antibacterial ointment used for preventing infections in minor wounds.

3.2 Triple Antibiotic Creams

This drug is also used in various triple antibiotic creams that include bacitracin and polymyxin B. These products are designed to cover a wide range of bacterial pathogens, offering a broad-spectrum antibacterial effect.

Dosage and Administration

Neomycin is given in different ways, but its absorption in the gut is limited, similar to other antibiotics like aminoglycosides. While it’s often taken by mouth, it’s also available as a cream or ointment for localized use.

Adult Dosage

Hepatic Coma Treatment

Dosage: For hepatic coma, the typical dose is 1000 to 3000 mg by mouth every 6 hours for up to 6 days. However, for managing hepatic encephalopathy, other medications like rifaximin and lactulose are preferred according to guidelines. It is specifically used in cases of severe hepatic encephalopathy.

Surgical Prophylaxis

Dosage: Before surgery, 1000 mg of neomycin is typically given orally, often with erythromycin or metronidazole, at specific times the day before the procedure.

Special Patient Considerations

Hepatic Impairment

There aren’t specific dose adjustments mentioned for liver issues in the manufacturer’s instructions.

Renal Impairment:

Similarly, there aren’t explicit dosage adjustments for kidney problems in the manufacturer’s instructions. However, caution is necessary as incorrect dosing can lead to high blood levels and potential toxicity.

Pregnancy:

Neomycin can cross the placenta and have harmful effects on the fetus. It’s classified as a Category C drug by the FDA, meaning it should only be used during pregnancy if needed after weighing the risks and benefits.

Breastfeeding

It’s unclear how much neomycin passes into breast milk. While aminoglycosides generally aren’t excreted much in breast milk, cautious monitoring is advised for any potential effects on the infant’s gut flora.

Pediatric Use:

• Neomycin’s safety and effectiveness in children under 18 aren’t well-established. When used in hepatic encephalopathy, the dosage should not exceed 100 mg/kg/day, divided into four doses, and the treatment shouldn’t last more than a week.

Older Adults:

• There aren’t specific dose adjustments for older adults in the manufacturer’s instructions. However, it’s advisable to check kidney function before starting neomycin therapy.

Pharmacokinetics

Understanding the pharmacokinetics of neomycin is crucial for optimizing its use and minimizing potential side effects.

Absorption

Neomycin is poorly absorbed from the gastrointestinal tract when administered orally, with less than 3% of the dose reaching the systemic circulation. This property makes it suitable for localized treatment of intestinal infections without significant systemic exposure.

Distribution

Once absorbed, neomycin distributes mainly in extracellular fluid. It does not readily cross the blood-brain barrier or penetrate tissues deeply, limiting its use to localized infections.

Metabolism and Excretion

Neomycin is not significantly metabolized in the body. It is excreted unchanged in the urine, with the majority of the drug eliminated within 24 hours. Due to its renal excretion, patients with impaired kidney function require careful dosing to prevent toxicity.

Side Effects

While neomycin is effective against bacterial infections, it also carries the risk of side effects, particularly with prolonged use or in high doses.

Nephrotoxicity

It causes damage to the kidneys, particularly in patients with pre-existing renal conditions or those receiving other nephrotoxic drugs. Monitoring kidney function during treatment is essential to prevent irreversible damage.

Ototoxicity

One of the most significant risks associated with this drug is ototoxicity, which leads to permanent hearing loss. This side effect is dose-dependent and more likely with prolonged systemic exposure. Symptoms include tinnitus, vertigo, and hearing loss.

Allergic Reactions

Some patients may experience allergic reactions to neomycin, ranging from mild skin rashes to severe anaphylaxis. It is important to screen for allergies before prescribing or using the medication.

Other Side Effects

Other possible side effects include gastrointestinal disturbances, such as nausea, vomiting, and diarrhea, especially when taken orally. Localized reactions, such as redness and itching, may occur with topical use.

Drug Interactions

1. Abacavir

   • Interaction: This may decrease the excretion rate of neomycin.
   • Effect: This could result in higher serum levels of neomycin.

2. Acarbose

   • Interaction: The metabolism of acarbose can be decreased.
   • Effect: Potential for increased effects or side effects of acarbose.

3. Aceclofenac

   • Interaction: The risk or severity of nephrotoxicity can be increased.
   • Effect: Higher likelihood of kidney damage.

4. Acemetacin

   • Interaction: The risk or severity of nephrotoxicity can be increased.
   • Effect: Higher likelihood of kidney damage.

5. Acenocoumarol

   • Interaction: The risk or severity of bleeding can be increased.
   • Effect: Higher likelihood of bleeding complications.

Contraindications

These are the following health conditions in which Neomycin is contraindicated:

• Oral neomycin should not be administered in cases of intestinal obstruction.
• Oral neomycin should not be given to patients with a known history of hypersensitivity.
• Individuals who have experienced hypersensitivity or severe toxic reactions to other aminoglycosides might exhibit cross-sensitivity to neomycin.

Resistance

Bacterial resistance to neomycin is an emerging concern, as with all antibiotics. Resistance mechanisms include the production of aminoglycoside-modifying enzymes, efflux pumps, and changes in ribosomal binding sites.

Mechanisms of Resistance

Aminoglycoside-Modifying Enzymes: These enzymes modify neomycin by acetylation, phosphorylation, or adenylation, rendering it ineffective.

Efflux Pumps: Bacteria may develop efflux pumps that actively expel neomycin from the cell, reducing its intracellular concentration.

Ribosomal Modification: Mutations in the ribosomal RNA can decrease the binding of this medication reducing its ability to inhibit protein synthesis.

Strategies to Combat Resistance

To combat resistance, it is essential to use neomycin judiciously and in combination with other antibiotics when appropriate. Ongoing research is focused on developing new aminoglycosides with improved efficacy against resistant strains.

Neomycin in Research and Biotechnology

Beyond its clinical applications, it is also valuable in research and biotechnology.

Selective Agent in Cell Culture

It is used as a selective agent in cell culture to maintain and select genetically modified cells expressing neomycin resistance genes. This application is crucial in genetic engineering and recombinant DNA technology.

Tool for Studying Ribosomal Function

Researchers use this drug to study the function of ribosomes and protein synthesis. Its ability to bind specifically to the 30S ribosomal subunit makes it a useful tool for dissecting the mechanics of translation in bacteria.

Brand in Pakistan

CITRALIN is manufactured by PEARL PHARMACEUTICALS.

HEALIT is produced by ATCO LABORATORIES LIMITED.

MYCITRACIN PLUS is manufactured by PFIZER LABORATORIES LTD.

PLANODERM is produced by FRIENDS PHARMA (PVT) LTD.

XYLOAID is manufactured by BARRETT HODGSON PAKISTAN (PVT) LTD.

Conclusion

Neomycin remains a critical antibiotic despite the challenges of resistance and toxicity. Its broad-spectrum activity and effectiveness against Gram-negative bacteria make it indispensable for treating infections. However, careful use and monitoring are essential to minimize adverse effects and combat resistance. With ongoing research and responsible stewardship, neomycin will continue to be a valuable asset in the fight against bacterial infections.