Neomycin and Polymyxin B Sulfates and Hydrocortisone

Neomycin and polymyxin B sulfates and hydrocortisone is a triple-combination ear drop that pairs two antibiotics with a steroid to treat outer ear infections, most commonly acute otitis externa (swimmer’s ear). It has been a go-to prescription for decades, available as both a suspension and a solution, and remains one of the most widely used otic preparations in the United States. But the landscape around it has shifted: newer fluoroquinolone-based drops have entered the market, resistance patterns have changed, and safety concerns about using it when the eardrum is not intact have sharpened clinical guidelines.

What Each Ingredient Does

The formulation brings together three active components, each targeting a different part of the problem. Neomycin is an aminoglycoside antibiotic that works by interfering with bacterial protein synthesis, which kills a range of gram-positive and some gram-negative bacteria. Polymyxin B attacks from a different angle, disrupting the outer membranes of gram-negative organisms. Together, the two antibiotics cover the bacteria most commonly responsible for outer ear infections, including Pseudomonas aeruginosa and Staphylococcus aureus.

Hydrocortisone, the third component, is a mild corticosteroid. It reduces swelling, redness, and itching in the inflamed ear canal. This is not just about comfort. Inflammation in acute otitis externa can narrow the canal enough to trap moisture and debris, which feeds the infection. By calming that inflammatory response, the steroid helps the antibiotics reach the tissue they need to reach. Evidence from clinical reviews supports the idea that combining a topical antibacterial with a corticosteroid works better than using either one alone for reducing the signs and symptoms of outer ear infections.¹

What It Treats

The primary indication is acute diffuse otitis externa, the painful, swollen ear canal that often follows swimming, humid weather, or overzealous cleaning with cotton swabs. Your doctor may also prescribe it for certain other superficial bacterial infections of the ear canal or, less commonly, for infected surgical cavities of the ear. It is not intended for middle-ear infections (otitis media), viral ear conditions, or fungal ear infections.

Clinical practice guidelines recommend topical preparations as the first-line therapy for uncomplicated acute otitis externa, and this combination has long been one of the standard options.² Systemic (oral) antibiotics are generally unnecessary unless the infection has spread beyond the ear canal or the patient is immunocompromised.

How It Compares to Newer Fluoroquinolone Drops

Since the early 2000s, fluoroquinolone-based otic drops like ciprofloxacin/dexamethasone have become increasingly common alternatives. The clinical data generally shows that both options clear outer ear infections well, but the newer drops have a modest edge in head-to-head trials. In one study of culture-positive patients, clinical cure rates at day 18 were about 91% with ciprofloxacin/dexamethasone versus 84% with the neomycin/polymyxin B/hydrocortisone combination, a statistically significant difference.³ Microbiologic eradication rates told a similar story, with roughly 95% versus 86% in the same trial.

Another trial comparing ciprofloxacin alone (without a steroid) to the triple combination found clinical cure rates of about 87% and 81%, respectively, with the difference just missing statistical significance.⁴ A pooled analysis of two trials found the mean time to cure was roughly half a day shorter with ciprofloxacin/dexamethasone compared with the older combination, a small but consistent advantage.⁵

Pain relief also tends to come faster with ciprofloxacin/dexamethasone. One analysis found that severe pain decreased rapidly within the first twelve hours of treatment with the newer drops, whereas patients on the older combination actually experienced a brief increase in pain during that same window.⁶ Inflammation and edema scores were also significantly better with ciprofloxacin/dexamethasone at follow-up.

So why does the older combination remain so widely prescribed? Cost is a big factor. Generic neomycin/polymyxin B/hydrocortisone drops are substantially cheaper than brand-name fluoroquinolone formulations, and for many patients with uncomplicated swimmer’s ear, the clinical difference between an 84% and a 91% cure rate is not dramatic enough to justify a much higher copay. Practice guidelines acknowledge this reality, recommending that the choice of topical therapy should weigh efficacy, adverse-event profile, likelihood that the patient will complete the course, and cost.⁷

The Neomycin Allergy Problem

One of the most clinically relevant drawbacks of this combination is contact allergy to neomycin. Neomycin is among the more common sensitizers in topical medications. When someone develops a contact allergy, applying the drops makes the ear canal redder, more swollen, and itchier instead of better, which can be difficult to distinguish from a worsening infection. The result is that doctors sometimes prescribe more of the same drops for what they think is a stubborn infection, when the real culprit is an allergic reaction to the medication itself.

How common is this? A large Danish study of consecutively patch-tested eczema patients found an overall prevalence of contact allergy to neomycin of about 1.4%, with a slight decline over time from around 1.8% in the earlier years to 1.2% more recently.⁸ The allergy was more common in patients over 40 and in those with facial dermatitis. A systematic review and meta-analysis pulled together data from 70 studies examining neomycin contact allergy rates in dermatitis patients across different populations.⁹ Keep in mind that these figures are for people already being evaluated for skin problems, so the rate in the general population is lower. Still, neomycin allergy is common enough that clinicians should consider it whenever a patient’s ear is not improving on these drops.

Fluoroquinolone-based alternatives do not carry this contact sensitization risk, which is one reason some ear specialists default to them, especially in patients with a history of skin sensitivities or repeated ear infections that require multiple courses of treatment.

Ototoxicity and the Perforated Eardrum

This is probably the single most important safety consideration with this combination. Aminoglycosides like neomycin are well-established ototoxins: they can damage the delicate hair cells of the inner ear, causing hearing loss that may be permanent. When the eardrum is intact, topical drops stay in the outer ear canal and the risk is minimal. But when the eardrum has a perforation, whether from infection, trauma, or a surgically placed ventilation tube, the drops can pass through into the middle ear and potentially reach the inner ear through the round window membrane.¹⁰

A large retrospective study looked at sensorineural hearing loss in patients with non-intact tympanic membranes who received neomycin-containing eardrops. It found that two prescriptions of neomycin carried an adjusted hazard ratio of about 1.45 for hearing loss compared with patients who did not receive neomycin, though the confidence intervals for a single prescription or three or more prescriptions did not reach statistical significance.¹¹ The signal is not overwhelming, but it is concerning enough that guidelines are explicit: if the patient has a known or suspected perforation of the eardrum, including a tympanostomy tube, clinicians should prescribe a non-ototoxic preparation instead.¹²

In practice, this means fluoroquinolone drops are strongly preferred when the eardrum might not be intact, since they have no demonstrated ototoxic potential at topical concentrations. If you’ve been prescribed neomycin/polymyxin B/hydrocortisone and you have ear tubes or a history of eardrum perforations, it is worth confirming with your doctor that your eardrum was inspected and is intact before using them.

Resistance Trends

The bacteria responsible for otitis externa are not standing still. A study comparing pathogen susceptibility between clinical trials conducted in the mid-1990s and those conducted around 2000 found that the minimum inhibitory concentrations for both neomycin and polymyxin B had increased markedly. By the later period, the mean concentrations needed to inhibit the major ear-canal pathogens had risen above the breakpoint for polymyxin B, suggesting that the organisms most commonly causing otitis externa were developing resistance to both antibiotics in the combination.¹³ No similar trend was seen for fluoroquinolones at that time.

A combined analysis of bacteriologic outcomes from clinical trials found that persisting P. aeruginosa and S. aureus isolates remained susceptible to both fluoroquinolones and neomycin/polymyxin B, which complicates the picture somewhat.¹⁴ The takeaway is not that the older combination has stopped working entirely. Rather, it’s that resistance is trending in an unfavorable direction, and in treatment-resistant cases or recurrent infections, the older antibiotic pairing may be less reliable than it once was.

This is worth keeping in perspective. Most uncomplicated cases of acute otitis externa still resolve on the older drops. But if your symptoms are not improving after a few days of treatment, resistance is one possible explanation, alongside contact allergy and fungal superinfection.

Fungal Superinfection Risk

Any antibiotic ear drop, not just this one, can set the stage for otomycosis, a fungal infection of the ear canal. Antibiotics kill off the normal bacterial flora that competes with fungi, and the steroid component suppresses local immune defenses. Together, these create a friendlier environment for fungal organisms like Aspergillus and Candida to take hold.

A systematic review found that ototopical antibiotics, with or without steroid drops, were the single most common predisposing factor for otomycosis, identified in roughly 47% of cases.¹⁵ Other major risk factors included the use of oils and wax solvents and trauma to the ear canal from aggressive cleaning. The review’s authors suggested that for mild cases of otitis externa, clinicians should consider alternatives like dilute acetic acid (essentially, a mild vinegar solution) to reduce the risk of fungal complications.

Otomycosis typically shows up as persistent itching, a feeling of fullness in the ear, and sometimes visible white, black, or yellowish debris on examination. If you’ve finished a course of antibiotic ear drops and your symptoms have changed character rather than resolved, a fungal infection is worth considering.

How to Use the Drops Properly

Getting ear drops to actually reach the infected tissue sounds straightforward, but a surprising number of patients use them incorrectly. Clinical guidelines specifically recommend that clinicians take the time to instruct patients on proper administration, not just hand over a prescription.¹⁶

The basic technique: lie on your side with the affected ear facing up. Gently pull the outer ear up and back (in adults) to straighten the ear canal, instill the prescribed number of drops, and stay in that position for three to five minutes so the medication can travel down the canal. Gently pressing on the tragus (the small flap in front of the ear canal) a few times can help work the drops deeper. Resist the urge to insert cotton afterward, as it can wick the medication back out.

When the ear canal is badly swollen, the drops may not be able to get past the narrowed opening. In that case, your doctor may need to perform aural toilet, which means carefully suctioning or swabbing debris and discharge from the canal, or place a small ear wick. The wick is a compressed sponge that is inserted into the swollen canal; when you apply drops, the wick expands and holds the medication against the inflamed tissue. It usually falls out on its own as the swelling resolves, or your doctor removes it at a follow-up visit.

A typical course of treatment is three to four drops in the affected ear three to four times daily for seven to ten days, though your doctor may adjust this depending on severity. Completing the full course matters even if symptoms improve within a day or two. Stopping early increases the chance of relapse and, potentially, of selecting for resistant organisms.

When to Use Something Else

Given everything above, there are several situations where this combination is not the best choice:

Perforated eardrum or ear tubes: Use a non-ototoxic fluoroquinolone drop instead to avoid the risk of hearing damage.
Known neomycin allergy: If you’ve ever had a contact reaction to neomycin, found in many over-the-counter antibiotic ointments as well, steer clear.
Suspected fungal infection: Antifungal ear drops or a topical antifungal agent is appropriate, not more antibiotics.
Chronic or recurrent otitis externa: Repeated courses raise the cumulative risk of sensitization and fungal complications. Your doctor may prefer a fluoroquinolone or investigate an underlying cause like a skin condition or anatomic issue.
Infection extending beyond the canal: If there is spreading cellulitis, fever, or any suspicion of malignant (necrotizing) otitis externa, systemic antibiotics and more aggressive management are needed.

The Suspension Versus Solution Distinction

You may notice that your prescription specifies either a suspension or a solution. The suspension contains tiny undissolved particles of hydrocortisone and needs to be shaken before each use so the steroid is evenly distributed. The solution has all ingredients fully dissolved and does not need shaking. Both deliver the same active ingredients at the same concentrations.

The practical difference is minor for most patients. Suspensions can leave a residue in the ear canal that sometimes needs to be cleaned out at follow-up visits, particularly if the canal is narrow or heavily inflamed. Solutions tend to flow more easily into tight spaces and may be somewhat easier to deliver through an ear wick. Neither formulation has been shown to be clinically superior to the other, and your pharmacy will typically dispense whichever version your doctor prescribes or whichever is available in generic form.

Off-Label Uses and Limits

Though the labeled indication is otic (ear) use, some practitioners have historically used neomycin/polymyxin B/hydrocortisone drops on the skin for superficial infected wounds or dermatoses. This off-label use has fallen out of favor for a few reasons. Neomycin’s contact sensitization rate makes it less desirable than other topical antibiotics for skin use, and the hydrocortisone concentration in the otic formulation is relatively low compared with what dermatologists typically prescribe for inflammatory skin conditions. Dedicated topical antibiotic and corticosteroid preparations designed for skin application are a better fit.

This combination should never be used in the eyes. Despite the similarity in dropper-bottle packaging, otic and ophthalmic formulations are not interchangeable. Ophthalmic preparations must meet sterility and pH standards that otic drops do not, and the neomycin/polymyxin B otic formulation can cause severe eye irritation or damage if instilled into the eye by mistake. Keeping ear drops and eye drops in separate, clearly labeled locations is a simple precaution that prevents a genuinely harmful mix-up.