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Oral and Topical Antibiotics in Acute Otitis Externa Treatment

Both topical and oral antibiotics are the primary treatment for external otitis because the most common cause is a bacterial infection. External otitis is an inflammation of the external acoustic meatus (EAM) skin. External otitis is also called swimmer's ear because it is often related to swimming or humidity. The prevalence of external otitis reaches 10% worldwide and can affect all ages.

Oral and Topical Antibiotics in Acute Otitis Externa Treatment
Otitis Externa


Due to prolonged moisture, the desquamation of the skin can form gaps that provide a port of entry for pathogenic microorganisms. The risk factors associated with the incidence of otitis externa are trauma (including the result of picking the ear), the presence of a foreign body in the EAM, wearing a hearing aid, chronic otorrhea, immunocompromise, and various skin or anatomical disorders of the EAM. The most common causes of external otitis are Pseudomonas aeruginosa and Staphylococcus aureus.

External otitis can be divided according to the time of occurrence, or the pathology that occurred. Based on time, acute if it lasts less than six weeks. Acute otitis externa is then subdivided according to the shape of the deformity. Diffuse otitis externa is external otitis with undefined lesions, whereas otitis externa circumscripta or furunculosis, is well-defined and is associated with hair follicle infection. Acute diffuse otitis externa is the most common form.

Based on the pathology that occurs, external otitis is divided into eczematous and necrotizing (malignant). There is an association betweenEczematous external otitis with skin disorders (such as atopic dermatitis, psoriasis, and systemic lupus erythematosus) that can extend to the external acoustic canal skin. In rare cases, the infection can spread to the soft tissue under the skin or bone around the EAC; this is known as malignant external otitis, an emergency disorder that requires immediate treatment.


Management of Acute Otitis Externa

Diagnosis of acute otitis externa is generally carried out by history taking and evaluating for signs of inflammation of the external acoustic canal using an otoscope.

Complaints: discomfort to ear pain, itching, fullness, hearing loss, tinnitus, or pain when opening and closing the mouth.
Physical examination: inflammation signs (hyperemia or edema of the tragus, auricles, and EAM, sometimes with otorrhea). In most cases, pain can also be found on palpation of the tragus or withdrawal of the auricle.
External otitis can also cause erythema of the tympanic membrane, so examining a pneumatic otoscope or tympanometry can be useful in differentiating it from medial otitis. It is essential to identify the tympanic membrane if it is intact to determine whether a particular antibiotic is contraindicated.

Most patients with acute otitis externa are treated empirically, with the principle:

  • pain management
  • clearance of debris in the external acoustic canal
  • edema and infection control
  • do not aggravate the existing situation

The main treatment for acute otitis externa is managing the infection. Bacteria is the majority cause of infections in otitis externa, so antibiotics are highly recommended. There are currently two antibiotic preparations available, namely ear drops and oral, each of which has its advantages and disadvantages. Surgery is considered in cases of malignant otitis externa or when complications such as EAC stenosis occur.

Microbiology of Acute External Otitis

A study in 2002 reported the pattern of microorganisms in 2,039 sufferers of acute otitis externa. This study found that 53% of cases were caused by gram-negative bacteria and 45.3% by gram-positive bacteria. The species most frequently found were Pseudomonas aeruginosa (71.3% of all gram-negative bacteria), followed by Staphylococcus epidermidis and Staphylococcus aureus.

Wiegand et al. presented similar data that more than 90% of acute external otitis cases are bacterial infection. This study reported Pseudomonas aeruginosa as the most common pathogen (22–62%), followed by Staphylococcus aureus (11–34%). Also, there were causes other than bacteria, namely fungi, in 2-10% of cases.

Topical Antibiotics in Acute otitis externa

Topical antibiotics (aminoglycosides, polymyxin B, and quinolone) are treatment options for acute external otitis. Various studies stated that the antibiotic group, either monotherapy or combined, had no significant difference in terms of its efficacy. Culture and antibiotic sensitivity testing are rarely necessary.

Currently available topical antibiotics are combined with or without corticosteroids. These corticosteroids are reported to have a significant impact on overcoming inflammation and reducing complaints faster. The selection of topical antibiotics need to pay attention to tympanic membrane condition, the risk of side effects that can occur, patient compliance, and cost-efficacy.

The neomycin-polymyxin B-hydrocortisone combination is the first-line treatment option when the tympanic membrane is intact. However, if tympanic membrane perforated and a history of allergy with aminoglycosides, so the topical antibiotics of choice are quinolone.

In most cases, clinical response is obtained within 48 to 72 hours, but a full response is not achieved until at least six days. If the response is inadequate, it is necessary to evaluate for CEA obstruction, foreign bodies, co-factors, or bacterial resistance.

Constraints to Topical Antibiotics
Patient adherence is sometimes an obstacle in administering topical antibiotics because of the frequency and technique of administration that requires the patients to lie on their side with the affected ear facing upwards so that the drug can be retained in the CEA for at least 3–5 minutes. 

Sometimes, ear drops' administration requires the help of others, as it is reported that only 40% of people can adequately administer ear drops themselves. Currently, Research is being carried out regarding ciprofloxacin suspension as the nontoxic topical antibiotic, given once a day, with a duration of 5 minutes.

In cases where edema leads blocked EAC, topical antibiotics are difficult to insert into the ear canal, and evaluation of the tympanic membrane may be difficult. Insertion of an ear tampon can allow topical antibiotics to enter inaccessible areas until EAC patency is achieved again.

Oral Antibiotics in Acute otitis externa

Various clinical guidelines state that administering oral antibiotics can be considered in acute otitis externa with infections that have extended beyond the skin layer of the external acoustic canal. So that topical drugs are thought to be ineffective. Oral antibiotics should also be considered in immunocompromised persons, or topical antibiotics are contraindicated.

The preparation chosen should have a broad spectrum and is empirically proven to be able to eliminate Pseudomonas aeruginosa or Staphylococcus spp. Chronic otitis externa is generally associated with allergies or other conditions, and it is not an indication of oral antibiotics.

Constraints on Giving Oral Antibiotics

Oral antibiotics are more at risk of causing side effects, bacterial resistance, and recurrence. Some more common side effects are skin rashes, vomiting, diarrhea, allergic reactions, and disturbances in the nasopharyngeal flora.

Compared to topical therapy, the concentration in infected tissue is much lower when otitis externa is treated with oral antibiotics. Topical therapy can provide concentrations 100 to 1000 times higher than that achieved with oral administration.


Efficacy of Topical vs. Oral Antibiotics in Acute Otitis Externa Treatment

To date, no studies have directly compared the efficacy of topical and oral antibiotics in otitis externa. However, a comparison between topical antibiotics and placebo shows that 65–90% of patients experience clinical resolution after receiving topical antibiotics for 7 to 11 days. Topical preparations have been reported to be effective in treating mild-moderate acute otitis externa.

A study analyzed by the American Academy of Otolaryngology-Head and Neck Surgery Foundation (AAO-HNSF) showed no significant difference in cure rates between patients were given topical ointments and oral antibiotics than when they were given topical ointments and placebo. Other studies also showed no difference in pain duration or bacteriological efficacy between topical ciprofloxacin-hydrocortisone versus the combination of oral amoxicillin with topical neomycin-polymyxin B-hydrocortisone.

In 2014, the AAO-HNSF issued recommendations related to the management of otitis externa, including:
  • Topical preparations should be given as initial therapy for diffuse otitis externa and acute otitis externa without complications.
  • Systemic antibiotics are not recommended as initial therapy in cases of otitis externa without complications, given for cases of infection with more expansion of the external acoustic meatus (EAM) layer.
  • Instruct the patient to apply topical medication, perform EAM cleaning, and insert tampons if EAM obstruction appears
  • Choose a non-ototoxic topical preparation if suspected or found that the tympanic membrane is not intact or a tympanostomy tube is attached.
  • Confirm the diagnosis of acute otitis externa and reassess the differential diagnosis if, within 48-72 hours of starting therapy, complaints persist.

The risk of antibiotic resistance in acute otitis externa is believed to be very low with topical antibiotics because of the high concentration of drugs in EAM compared to systemic antibiotics. The risk of resistance to topical antibiotics can also be prevented because their elimination is selective only for bacteria in the EAM and does not affect normal flora in other parts of the body. Restriction on the use of systemic antibiotics is important, given the increasing incidence of resistance to Pseudomonas aeruginosa or Staphylococcus spp.


Conclusion
Acute external otitis is inflammation or infection of the external acoustic meatus and/or auricle. The bacterial infection is the most common cause, so antibiotics are the main treatment.

Scientific evidence and existing clinical guidelines have shown that topical antibiotics are suitable first-line therapy for uncomplicated acute otitis externa. Oral antibiotics in cases of uncomplicated otitis externa should be avoided unless the infection extends beyond the skin layer of the EAM or in high-risk patients such as immunocompromised patients. Excessive use of oral antibiotics increases the risk of side effects, resistance, and recurrences.

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