Why was neomycin discontinued? Understanding the Safety Risks

October 10, 2025 •

4 min read

According to a 2019 notice from the Food and Drug Administration (FDA), an abbreviated new drug application for nonsterile neomycin sulfate powder was withdrawn due to safety concerns, including ototoxicity, nephrotoxicity, and neuromuscular blockade. This decision highlights the serious risks associated with the antibiotic and explains why systemic uses of neomycin were discontinued. While topical forms containing neomycin remain available over-the-counter, its systemic administration has been largely abandoned due to these significant adverse effects.

Quick Summary

The discontinuation of systemic neomycin and restricted use of other formulations were driven by serious and potentially irreversible adverse effects. These include ototoxicity leading to permanent hearing loss, nephrotoxicity causing kidney damage, and the risk of neuromuscular blockade. The risk profile became too high compared to the availability of safer, more modern antibiotic alternatives.

Key Points

High Toxicity Profile: Neomycin's discontinuation was primarily driven by its high risk of causing severe, often irreversible damage to the kidneys (nephrotoxicity) and inner ear (ototoxicity).
Irreversible Ototoxicity: Neomycin is particularly known for its potential to cause permanent bilateral sensorineural hearing loss, even after the medication is stopped.
FDA Action: The Food and Drug Administration (FDA) formally withdrew approval for specific systemic neomycin products, like nonsterile compounding powder, due to evidence of systemic toxicity.
Neuromuscular Blockade Risk: A serious but less common adverse effect of systemic neomycin is neuromuscular blockade, which can lead to respiratory paralysis.
Topical Use Continues: Neomycin remains a common ingredient in over-the-counter topical antibiotic ointments (e.g., Neosporin), where systemic absorption is minimal.
Modern Alternatives: Safer and more effective antibiotics have replaced systemic neomycin, making its high-risk profile unnecessary for most therapeutic uses.
Bacterial Resistance: Like many older antibiotics, neomycin has faced issues with bacterial resistance, further limiting its effectiveness.

What is Neomycin and its History?

Neomycin is an aminoglycoside antibiotic discovered in 1949 by Selman Waksman. It was initially hailed as a breakthrough due to its broad-spectrum activity against many types of bacteria, including some resistant to streptomycin. Early in its history, it was used both systemically (via injection) and locally (as a topical ointment) for a variety of infections. However, early clinical reports quickly identified significant toxicity concerns, particularly with systemic administration. These side effects led to its limited use, primarily to non-systemic applications like bowel preparation and topical ointments.

The Major Adverse Effects that Led to Discontinuation

The primary reasons behind the discontinuation of systemic and compounded neomycin center on three key adverse effects that can result from systemic exposure. These toxicities, often severe and sometimes irreversible, made the risk-to-benefit ratio of neomycin unacceptable for many applications, especially compared to newer, safer antibiotics.

1. Ototoxicity Neomycin is known to be the most ototoxic of all aminoglycosides, with its effects often being irreversible. Ototoxicity involves damage to the cochlea, which can lead to permanent bilateral sensorineural hearing loss.

How it happens: Neomycin damages the sensory hair cells of the inner ear, leading to hearing impairment. This damage can be delayed, meaning hearing loss might not be apparent until after treatment has concluded, making it particularly insidious.
Vulnerable populations: Premature infants, neonates, and the elderly are especially susceptible to this effect due to higher sensitivity.

2. Nephrotoxicity Nephrotoxicity, or kidney damage, is another major concern associated with systemic neomycin exposure. While often reversible if the drug is stopped, prolonged use can lead to serious kidney injury.

Mechanism of damage: The antibiotic accumulates in the renal tubules, disrupting kidney function. This can result in decreased urination and elevated levels of waste products in the blood.
Risk factors: Pre-existing kidney problems, dehydration, advanced age, and prolonged treatment duration increase the risk of nephrotoxicity.

3. Neuromuscular Blockade In rare but serious cases, neomycin can induce neuromuscular blockade, which can lead to respiratory paralysis. This risk increases when the antibiotic is combined with anesthetics or muscle-relaxing drugs.

Comparison of Neomycin vs. Modern Alternatives

To understand why neomycin's use has declined, it's helpful to compare its toxicity and efficacy with other common antibiotics. This table highlights some key differences.


Feature	Neomycin (Systemic)	Modern Antibiotics (e.g., Cephalosporins)
Toxicity	High risk of ototoxicity and nephrotoxicity.	Generally lower risk of severe, irreversible organ toxicity.
Absorption	Poorly absorbed from the gastrointestinal tract, leading to minimal systemic exposure in oral form.	Designed for reliable systemic absorption for treating a wide range of infections.
Effectiveness	Broad-spectrum, but significant resistance has developed over time.	Targeted to specific types of bacteria, with ongoing development to counter resistance.
Availability	Systemic forms largely withdrawn or severely restricted.	Widespread availability for a broad range of infections.
Route of Administration	Oral (limited use), topical (common). Parenteral forms largely discontinued due to extreme toxicity.	Oral, intravenous, topical, depending on the specific drug.

The FDA's Role and Specific Withdrawals

The FDA has played a critical role in limiting the use of neomycin by withdrawing approval for certain forms. Most notably, in 2019, the FDA withdrew the approval for nonsterile neomycin sulfate powder for prescription compounding. This action was based on clinical evidence showing significant toxicity from systemic exposure, even from compounded preparations. Separately, manufacturers have also discontinued their versions of oral neomycin tablets due to market dynamics and safety profiles.

Current Use of Neomycin Despite the discontinuation of systemic forms, neomycin has not been entirely removed from the market. It continues to be used in formulations where systemic absorption is minimal or controlled. The most common modern applications include:

Topical Ointments: Neomycin is a key ingredient in many over-the-counter triple antibiotic ointments, like Neosporin, combined with bacitracin and polymyxin B. In this form, it helps prevent infection in minor cuts, scrapes, and burns, as absorption is very low.
Eye and Ear Drops: For localized infections, neomycin is still used in some prescription eye and ear drops.
Oral Preparations (Restricted): In highly specific cases, such as the management of hepatic encephalopathy or bowel sterilization before surgery, oral neomycin may still be used under careful medical supervision. This is because the drug's poor absorption in the gut allows it to kill ammonia-producing bacteria in the intestines, but strict monitoring is required due to the risk of toxicity if a compromised gut wall allows systemic absorption.

Resistance to Neomycin

Another factor influencing neomycin's declining use is the development of bacterial resistance. As with many older antibiotics, overuse can lead to resistant strains of bacteria, making the medication less effective over time. The potential for cross-resistance to other aminoglycosides is also a concern.

Conclusion

The discontinuation and restricted use of neomycin were driven by a clear understanding of its significant safety risks, particularly irreversible ototoxicity and potentially severe nephrotoxicity. While its topical and specific oral applications remain relevant, the evolution of pharmacology has provided safer, more targeted alternatives for systemic infections. The FDA's withdrawal of compounded neomycin in 2019 serves as a final official confirmation that the risks of systemic exposure outweigh the benefits, reinforcing the shift towards more modern and secure treatment options. The lessons learned from neomycin's toxicity continue to influence drug safety monitoring and development today.

For more information on drug safety and pharmacology, consider visiting the National Institutes of Health (NIH) website.

Frequently Asked Questions

No, neomycin has not been completely banned, but its systemic use has been largely discontinued due to severe toxicity. It is still widely available and used in topical forms, like antibiotic ointments and some ear/eye drops, where it has minimal systemic absorption.

The most dangerous side effect of neomycin is irreversible ototoxicity, which can cause permanent bilateral hearing loss. This risk is so significant that it led to the withdrawal of systemic formulations.

Yes, you can still use Neosporin and other triple antibiotic ointments that contain neomycin. These products are for topical use on minor cuts and scrapes, and the neomycin is poorly absorbed through the skin, minimizing the risk of systemic side effects.

A wide range of safer and more modern antibiotics are now used as alternatives to systemic neomycin. The specific choice depends on the type of infection, but examples include different classes of antibiotics like cephalosporins and macrolides, among others.

Yes, even oral neomycin can cause systemic side effects, particularly if a patient has impaired kidney function or gastrointestinal inflammation. This is because it can be absorbed through the compromised intestinal lining, leading to the same ototoxicity and nephrotoxicity risks as systemic administration.

Patients most at risk for neomycin toxicity include the elderly, premature infants, and those with pre-existing kidney problems or underlying conditions like myasthenia gravis. Dehydration and high doses or prolonged treatment also increase the risk.

Neomycin is still used orally in some cases to treat hepatic encephalopathy, a complication of liver disease. It is poorly absorbed and works by killing ammonia-producing bacteria in the gut, which helps reduce ammonia levels in the bloodstream. However, this is done with careful medical supervision to monitor for systemic absorption and toxicity.