What are ototopical antibiotics?
Ototopical antibiotics are applied as the first-line offence against middle ear infection.
Ototopical antibiotics are medications administered topically in the ear for treating middle ear infections. Ototopical antibiotics are usually the first-line treatment for recurrent bacterial ear infections, in the absence of systemic infection.
Ear infections are more common in children, and often clear up on their own. Most ear infections can be managed with warm compresses and pain management. Antibiotics are usually administered only for severe and persistent ear infections.
What are the advantages of ototopical antibiotics?
Administration of antibiotics directly in the ear has several advantages over systemic delivery including the following:
Antibiotic concentration
Topical antibiotic solutions contain vastly greater concentration of antibiotic than the medications administered orally, or even intravenously. The high antibiotic concentration, delivered directly at the site of the infection, is much more effective in killing the bacteria. It also reduces the possibility for development of antibiotic-resistant bacterial strains.
The lowest level of drug concentration that can prevent bacterial growth is known as minimum inhibitory concentration (MIC). Some drug-resistant bacteria have a high MIC, but ototopical antibiotics far exceed the MIC required for destroying even highly resistant bacteria.
Absence of systemic effects
The absence of systemic effects with topical administration eliminates the risk of systemic antibiotic side effects. The normal beneficial bacteria that live in the respiratory and gastrointestinal tracts are unaffected. Absence of systemic antibiotics also prevents the natural selection and proliferation of drug-resistant bacteria.
Alteration of microenvironment
Topical administration allows alteration of the ear canal’s microenvironment to control bacterial proliferation. The normal pH of the ear canal is slightly acidic. The natural defense mechanism of the ear canal can be enhanced by delivering the antibiotic in an acidic solution, which makes the microenvironment even more inhospitable for bacterial growth.
Treatment cost
Ototopical antibiotics are generally less expensive than comparable systemic medications.
What are the disadvantages of ototopical antibiotics?
Ototopical antibiotics have a few disadvantages as well, which include the following:
Difficulty in delivery
Direct delivery at the infection site may be difficult or impossible sometimes. The medication may fail to reach the infected area in the middle ear if the ear canal is blocked due to:
- Excessive and hardened earwax
- Excessive discharge from infection
- Block in the ear tubes inserted for fluid drainage from the middle ear
- Swollen or overgrown tissue (granulation)
Steps must be first taken to clear the blocks before antibiotic administration. Irrigating the ear canal can easily clear a block caused by earwax and other secretions, but an ear tube block and granulation each may require some procedure and other medications.
Ototoxicity
Ototoxicity is toxicity to the ear from local administration. Ototoxicity can irritate and inflame the mucus membranes of the middle ear. If the antibiotic enters the inner ear, it may lead to:
- Hearing loss
- Tinnitus
- Vertigo
- Sensitivity reaction
Ototopical antibiotics can cause allergic reactions. Low-grade sensitivity reactions may cause persistent drainage that may be impossible to distinguish from drainage due to infection, making treatment difficult. Some people may also develop cross-sensitivity to related antibiotics.
Absence of systemic effect
Absence of systemic effect may turn into a disadvantage if the infection extends outside the ear canal into the soft tissues of the cheek or external ears. Treatment with systemic antibiotics will be required if ear infection is accompanied by sinus or throat infection.
Alteration of microenvironment
Alteration of the ear’s microenvironment in an inappropriate way can turn counterproductive. Most bacteria grow best in neutral pH, but some bacteria thrive in acidic conditions, while a few others grow in alkaline environments. Antibiotics administered in an alkaline solution can create a hospitable environment for bacteria such as Pseudomonas that thrive in alkaline conditions.
What are the types of ototopical antibiotics?
Ototopical antibiotics are available in three forms:
Powders
Powders are not approved by FDA, but regionally compounded powders have been in use for years. Powders have the advantage of adhering to and remaining for a long time in moist surfaces. Powders are prepared with several components.
Two preparations of powders used are:
- Gold dust: comprised of chloramphenicol, sulfanilamide and hydrocortisone
- Mastoid powder: comprised of ciprofloxacin, clotrimazole, dexamethasone and boric acid
Creams and ointments
Creams and antibiotics are applied only for bacterial and fungal infections in the external ear and auditory canal, usually with a single dose. Following are some of the antibiotic ointments and creams used for external ear infections:
- Neomycin/polymyxin B/bacitracin (Neosporin)
- Tobramycin ointment
- Clotrimazole (Mycelex) for yeast infection (Candida)
- Mupirocin ointment
Drops
Drops are the most commonly used form of ototopical antibiotics. Drops are available as:
- Single agent solutions
- Combination products
- Combination products
In addition to antibiotics, medications added to ototopical combination products include the following:
Steroids to reduce inflammation and improve recovery
Antiseptics for use in external ear infections, because they have both antifungal and antibacterial properties. Some of the antiseptics used in ototopical preparations include:
- Gentian violet
- Mercurochrome
- Cresylate
Antifungal medications such as:
- Nystatin
- Clotrimazole
- Miconazole
- Tolnaftate
Some ototopical combination products do not have any antibiotics, instead relying on pH, viscosity and other chemical properties to kill the bacteria or control their growth by producing a hostile ear environment.
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Which antibiotic is best for an ear infection?
Two classes of antibiotics are commonly used to treat an infection.
Aminoglycosides
Aminoglycosides have been the main treatment for bacterial ear infections for decades. Two aminoglycosides used in ototopical preparations are:
- Neomycin
- Tobramycin
Though both of the above are commonly used in the United States, only neomycin has FDA approval. Neomycin is effective for gram-positive bacteria but its effectiveness against gram-negative bacteria has declined over years, especially against Pseudomonas, the most common bacteria in ear infections.
Tobramycin is effective for Pseudomonas and other gram-negative bacteria.
Quinolones
Quinolones are the most recently introduced ototopical antibiotics. Most quinolone antibiotics in use are fluoroquinolones, which also contain an atom of fluorine. Fluoroquinolones are considered the best available treatment now for ear infections for two reasons:
- Broad spectrum of activity against both gram-positive and gram-negative bacteria
- Lack of ototoxicity
Following are some of the FDA-approved fluoroquinolone solutions for external ear infection (acute otitis externa) from Staphylococcus aureus and Pseudomonas aeruginosa:
Ciprofloxacin (Cetraxal)
Side effects include:
- Application site pain
- Ear itching (pruritus)
- Fungal ear superinfection
- Headache
- Finafloxacin (Xtoro)
Side effects include:
- Pruritus
- Nausea
Ofloxacin (Floxin Otic)
Side effects include:
- Pruritus
- Application site reaction
- Combination ear drops
Cortisporin
Contains hydrocortisone, neomycin and polymyxin B.
Side effects include:
- Stinging
- Ototoxicity
- Neomycin allergy
Ciprodex
Contains ciprofloxacin and dexamethasone.
Side effects include:
- Pruritus
- Ear discomfort
- VoSol HC
Contains acetic acid and hydrocortisone.
Side effects include:
- Stinging
- Burning
Domeboro solution
Contains aluminum acetate and acetic acid.
Side effects include:
- Stinging
- Burning