Applied Evidence

Otitis externa: Providing relief while avoiding complications

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Treatment options may be equally effective, but risks of ototoxicity vary


 

References

Practice recommendations
  • Topical antimicrobial otic drops, supplemented by oral analgesics, provide prompt and effective therapy (B).
  • Fluoroquinolones and neomycinpolymyxin B combinations have shown equal efficacy (A), but the former are preferred when trying to guard against ototoxicity or hypersensitivity (C).
  • For severely painful otitis externa, consider inserting an ear wick and giving oral narcotics (C).
  • Localized cellulitis requires systemic antimicrobial therapy (C).
  • No compelling evidence exists on the effectiveness of astringent topical treatments for otitis externa. Also, topical astringents are often painful, which may impede adherence (B).

Widespread use of neomycin combinations may have led to an increase in the incidence of patient hypersensitivity and promoted antibiotic resistance in Staphylococcus aureus and Pseudomonas aeruginosa, the 2 most common pathogens of otitis externa (see Pathogens of otitis externa).

Recent controlled clinical trials have shown the effectiveness of otic fluoroquinolones, ofloxacin (Floxin Otic) and ciprofloxacin (Ciprodex), which have several clinical, microbiologic, and dosing advantages over older topical antibiotics. Fluoroquinolones are not ototoxic and are effective against S aureus and P aeruginosa.

The incidence of fluoroquinolone-resistant Pseudomonas in otitis externa is low, and hypersensitivity is quite rare. Although they are slightly more expensive than neomycin combinations, fluoroquinolones require only 1 or 2 daily doses, possess superior in vitro activity, and provide a better safety profile that favor their use in moderate to severe otitis externa.

Symptoms and complications to watch for

Pain, which may be incapacitating, is the predominant complaint and the only symptom directly related to disease severity.1,6 Patients may also experience discharge, itchiness, and, in some cases, temporary hearing loss.1,5 A fluffy white exudate may signal a rare fungal infection, perhaps complicating an underlying bacterial infection.

Bone involvement. A rare, extremely severe form of otitis externa, known as malignant (or necrotizing) otitis externa, is caused by a Pseudomonas infection that invades the posterior cranial bone. This life-threatening form of otitis externa affects primarily elderly patients with diabetes who live in hot, humid environments. Malignant otitis externa usually requires hospitalization and parenteral antibiotic therapy.7

Secondary cellulitis. Summer often ushers in several cases of another severe form of otitis externa in children, involving a secondary cellulitis of the pre- and postauricular skin structures. If an underlying mastoiditis is uncertain, consider ordering a computerized tomography scan and referring for an otolaryngologic exam. This cellulitis infection also requires aggressive broad-spectrum oral or parenteral therapy.

Elements of successful treatment

Most treated cases of otitis externa resolve completely within 5 days. In a study conducted in the Netherlands, 35 out of 98 adult patients discontinued daily activities for a median of 4 days, and the median duration of bed rest was 3 days.3

However, secondary skin and soft tissue infections can slow resolution. They may also develop if treatment is delayed or ineffective. For uncomplicated otitis externa, treatment with an appropriate topical antibiotic, plus potent analgesics to relieve pain, is the preferred therapeutic approach.4,8 Choosing the optimal topical treatment, however, requires knowledge of evolving resistance among pathogens, possible hypersensitivity to neomycin, adherence factors, and cost issues.

Topical antibiotics usually sufficient. Most cases of otitis externa without significant complications9 are effectively treated with just topical antibiotics; though, for more severe cases, I prefer to insert an ear wick and to use oral narcotics.7

In the 1970s to 1990s, topical combination preparations containing hydrocortisone and the antibiotics neomycin sulfate and polymyxin B were the mainstay of therapy for otitis externa.6,9 Approximately 5 years ago, topical fluoroquinolones became available for otitis externa. Given this range of antibiotic choices, physicians need to know the various treatment options and other modalities available.

Oral antibiotics. Additional oral or parenteral antibiotics are usually necessary for severe cases of otitis externa with secondary cellulitis or lymphadenitis.10,11 Oral antibiotics may also be necessary with concomitant disease at other sites (sinus, middle ear) or complications.

Pain relief. Nonsteroidal anti-inflammatory drugs (NSAIDs—eg, ibuprofen), acetaminophen, and narcotics (eg, codeine) are adjunctive measures for reducing ear pain.

Enabling compliance. Patient compliance, according to one systematic review, is inversely proportional to the prescribed number of doses per day.12 Adherence with twice-daily dosing was significantly better than with 4-times-daily dosing for oral and topical medications.12 Twice-daily dosing is accepted as readily as once-daily dosing12 and may maintain continuity of drug action better than a once-daily regimen in the event a dose is forgotten.13

Pathogens of otitis externa

Acute inflammation of the external auditory canal most often is caused by bacterial infection. Infrequently, a fungal infection may be the cause.

Pseudomonas aeruginosa and Staphylococcus aureus are the predominant bacterial pathogens associated with otitis externa.1,2 The pathogenesis involves modification of the natural antimicrobial defense mechanisms of the external ear canal. Under healthy conditions, cerumen (ear wax), which is secreted by sebaceous and apocrine glands in the external ear canal, is acidic and contains lysozyme, an antimicrobial substance. The ear canal becomes vulnerable to bacterial infection when the cerumen barrier is disrupted by scratching or scraping, or macerated by prolonged exposure to water. Disruption of the external ear’s epithelium, caused by seborrhea, eczema, or trauma, can also increase the risk of otitis externa. Because frequent swimming is the most common predisposing factor for the disease, otitis externa is commonly referred to as “swimmer’s ear.”1,3 As may be expected, the number of cases of otitis externa increases markedly during the summer months in temperate climates.4 The infection is uncommon in children aged less than 2 years.

Rarely, otitis externa appears to be caused by fungal infection.5 Such cases are not usually differentiated on clinical grounds, except when there is appearance of a fluffy white exudate. In most cases of fungal otitis externa, the fungus appears to be a superinfection after the bacterial infection. Thus, persistent otitis externa is typically treated with 2 or 3 courses of topical antibiotics before the clinician begins to investigate more specifically for fungal superinfection.

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