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OTITIS EXTERNA

Timothy C. Hain, MD Page last modified: November 3, 2018

DEFINITIONS

Otitis externa (OE) is an infection of external auditory canal. It is a dermatitis, not all that different from infections in other bodily orifices that don't get much fresh air or sun. Ear wax can provide a culture medium for bacteria. Cleaning of the ear canal can also sometimes be associated with scrapes that allow bacteria an opportunity to grow.

GENERAL SIGNS AND SYMPTOMS:

Persons with otitis externa present with pain, drainage and loss of hearing.

Otitis externa is most commonly caused by infections

Fungi (otomycosis) are usually accompanying organisms, but can also be the primary cause of otitis media or otitis externa.

Mites (demodex) are found in roughly 6% of normal human ears and are more common in ears where a local steroid preparation has been used. (Cevlik et al, 2014). Ear mite infection is occasionally are associated with extremely itchy external otitis (Klem et al, 2009). This should not come as a surprise to pet owners who are familiar with ear mites.

Treatment of Otitis Externa

Cultures of draining ears are recommended at the initial visit. However, the impact on management is uncertain.

The Cochrane metanalysis paper (2010) for acute otitis externa, stated that "Topical treatments alone, as distinct from systemic ones, are effective for uncomplicated acute otitis externa. In most cases the choice of topical intervention does not appear to influence the therapeutic outcome significantly." This was with the caveat that they were not sure if steroid-only drops were effective.

Following are a list of potential treatments, both for acute OE and more chronic OE.

Prevention measures for recurrence include the following (Sander, 2001)

When acidification fails, antifungal topical preparations are also commonly used. There are numerous of these agents used in animal medicine. None of these is presently FDA approved for human use and for this reason they are used "off-label" in humans. Several of these are available over-the-counter such as clotrimazole -- (Lotrimin AF) cream and tinactin solution. Use of these preparations should be under the supervision of a physician experienced in treating ear infections. Romsaithong et al (2016) reported that 1% clotrimazole solution was more effective than 3% boric acid in 70% alcohol.

Moshtaghi et al (2017) reviewed prices of ear drops in southern California, and stated:

"Data were collected from 108 pharmacies. The mean prices are noted for each of the individual drugs: Cortisporin (brand) 10 mL, $82.70; neomycin, polymyxin B sulfates, and hydrocortisone (Cortisporin-generic) 10 mL, $34.70; ofloxacin (generic) 10 mL, $99.95; sulfacetamide (generic) 15 mL, $40.18; Ciprodex (brand) 7.5 mL, $194.44 (or $218.60 according to the medical letter); Cipro HC (brand) 10 mL, $233.32 (or $298.00 according to the Medical letter; Vosol (brand) 15 mL, $120.75; acetic acid (Vosol-generic) 10 mL, $116.55; VosolHC (brand) 10 mL, $204.14; acetic acid/aluminum acetate (Domeboro-generic) 60 mL, $22.91; and Tobradex (brand) 5 mL, $166.47." Additionally, According to the Medical Letter, Otiprio (1 ml single dose) costs $283.20. This is roughly 4 times as much as generic ofloxacin 0.3% drops.

As can be seen, the least expensive treatment, on average, is Domeboro-generic ($22.91). This is actually an antiseptic treatment, with the mechanism being making the ear canal more acidic. The safest in regards to lowered risk of hearing loss should there be a perforation, as well as the least painful treatment (in our opinion) is moderately expensive (ofloxacin generic -- $99.95, which are $70.30 according to the Medical letter). One wonders why a generic is so expensive in the US.

Amazingly enough, drops made of acetic acid (e.g. Vosol-generic) cost $116.55. Considering the cost of the raw ingredients (i.e. vinegar and water), this seems high.

In our opinion, the generic ofloxacin 0.3% drops are presently the best choice for acute otitis externa considering price, safety and effectiveness.

Treatment of fungal external otitis.

This is generally recognized by failure or partial response to treatment for acute external otitis. Typical organisms are candida and aspergillus. One should rule out metabolic and immunological disorders, i.e. diabetes, cancer chemotherapy, leukemia, and HIV among others. The ear should be carefully cleaned, and an anti-fungal cream such as Nizoral or Lotromin considered. There shold be repeat cleaning and application of the antifungal every 10-14 days. (Farrior, 2000)

Eberconazole 1% otic solution was also reported as effective. (De la Paz Cota et al, 2018)

Treatment of ear mites.

Only a few cases have been reported of ear mites in humans. One paper reported treatment with topical hexachlorocyclohexane (Klemm et al, 2009). They suggested that a more contemporary treatment might be permethrin. These drugs are rarely used in humans and their effect is not well understood.

References

Copyright November 3, 2018 , Timothy C. Hain, M.D. All rights reserved. Last saved on November 3, 2018