Topical antibiotic treatment of acute uncomplicated otitis externa.

Dr. Billy Giles: Acute uncomplicated otitis externa is more common in adults than children. In children and adolescents, it is more prevalent in the summer months.

Otitis externa occurs as a result of trauma to the external ear canal. The most common source of damage overall is the misuse of cotton swabs; among children, the primary cause is fingernail trauma. Otitis externa is also caused by hearing aids and excessive moisture, especially during hot and humid weather. Such damage breaks down the normal defense mechanisms in the ear canal, which allows keratin debris to accumulate. The keratin absorbs water and becomes a medium for bacterial growth.

Symptoms include a significant amount of pain during chewing and movement of the ears, which can be disabling, and occlusion, which can impair hearing. One study found that 36% of patients experienced pain that was severe enough to disrupt their daily activities for a median of 4 days; 21% of these patients required bed rest. (1) I once treated a college football player who had a case of otitis externa that was so painful he was not able to practice. His coach did not understand how a big, strong, healthy young man could be so disabled by "an earache."

Treatment

Dr. Giles: Otologists know, and primary care physicians should know, that otitis externa represents a bacterial infection that requires antimicrobial treatment. Primary care physicians often believe that rinsing the ear canal with a bulb syringe is an effective technique, but this can be a dangerous and painful procedure. Improper toilet can lead to rupture of the eardrum. Cleaning the ear canal is an important part of treating external otitis, but doing it properly requires equipment that most primary care physicians do not often use--specifically, an ear microscope and suction.

Another reason we need to use antimicrobials is that we don't know exactly when the disease might make a transition from the ear canal to the surrounding soft tissue, and it's not economically feasible to obtain imaging studies to evaluate this. We do not want the pathology to spread beyond the local area to, say, the temporomandibular joint. From this standpoint alone, empiric topical antibiotic therapy makes sense. In the absence of clear clinical findings of limited involvement or in the presence of any systemic immunocompromising disease, it is better to use the antibiotic rather than run the risk of undertreating.

Arguments against antibiotics

Dr. Giles: Some might argue that antibiotics are not necessary or as desirable as other agents from the standpoint of economics, accessibility, and side effects. They might also contend that the prime consideration should be treating inflammation rather than infection.

Dr. John Rutka: That's right. The problem in acute otitis externa is the pain, and the pain is most likely caused by the inflammatory component of the disease, not the infectious component. Therefore, wouldn't it be better to use a steroid rather than an antibiotic?

Dr. Giles: No. The inflammation may cause the pain, but the infection causes the inflammation. In fact, the organisms are not pathologic until they cause inflammation. So I prefer to treat the cause as well as the symptom.

Dr. Rutka: In other parts of the world, physicians successfully use a variety of topical acidifying solutions and antiseptics. These preparations are effective, available, and relatively inexpensive, which is so important in less developed countries. For example, acidifying solutions--aluminum acetate, boric acid, etc.--are effective because Pseudomonas aeruginosa does not thrive in basic pH. The addition of an antiseptic such as ethyl alcohol helps prevent itchiness and also serves as a drying agent.

Dr. Giles: There is evidence that topical antiseptics are more effective than placebo. But we are not talking about patients in the Third World, we are talking about patients in North America. Antibiotics are available, they are more effective than antiseptics, and they are cost-effective, especially when a patient is able to return to work sooner. Also, if you put an antiseptic in a patient with a perforated eardrum, the patient is going to experience significant pain. Aluminum acetate, for one, can also be ototoxic in a patient with a perforated drum.

Dr. Rutka: The use of topical antiseptics and disinfectants is less likely to lead to bacterial resistance.

Dr. Giles: True, but resistance to ototopical quinolone antibiotics is not a major problem clinically.

Dr. Rutka: Another advantage of topical antiseptics and disinfectants is that they can be used for both bacterial and fungal infections. A topical antibiotic changes the flora of the ear canal and in certain circumstances can allow pathogenic fungi to spread and cause a secondary infection. This is especially worrisome when you don't know what type of infection you are dealing with initially.

Dr. Giles: This is true, but as physicians, we should be able to tell the difference between an acute bacterial infection and a fungal infection. If there is any question regarding the source of infection, then the patient probably does not have a severe bacterial infection, and an antiseptic may be appropriate. So I don't think this is a legitimate concern.

Dr. Rutka: One patch-testing study showed that 56% of patients with chronic otorrhea had a positive reaction to topical therapy; the biggest offenders were aminoglycoside antibiotics. (2)

Dr. Giles: The sensitivity issue is a straw man. Allergic reactions to topical antibiotics can be avoided simply by using a quinolone. An allergic reaction to a quinolone is possible, but it is very unusual.

Dr. Rutka: What about the possibility that a topical antibiotic will cause stenosis of the external ear canal with repetitive use, especially if a progressive chronic external otitis with subdermal hypertrophy occurs as a result of hypersensitivity & allergy?

Dr. Giles: This is theoretically possible, but I don't know why an antibiotic would cause stenosis and an antiseptic would not. At any rate, the addition of a steroid to a topical treatment should greatly reduce subdermal hypertrophy, which is already very uncommon considering the nature of the skin of the ear canal. I have seen canal stenosis only a very few times, and it always followed significant manipulation and trauma of the ear canal. I am not aware of any reports in the literature of stenosis caused by topical antibiotics.

Dr. Rutka: Actually, despite the fact that I have been playing the devil's advocate, I typically favor using a topical quinolone/steroid drop for many reasons. I have been a standing member of our provincial anti-infective guideline panel in Canada, and for some time I supported the use of topical antiseptics over antibiotics for otitis externa for the reasons we've already discussed. Among the factors on which I based my opinion were the results of two studies from the United Kingdom--one by Clayton et al (3) and one by Tsikoudas et al (4)--that were purported to be randomized, controlled trials in which the authors concluded that antibiotic treatment was not always required. However, I had not actually looked at the trial protocols. I wish I had because, even though I raised legitimate concerns, I later found out that the protocols really weren't as rigorous as they should have been. It was the typical case of someone reading the abstract and seeing the right words, yet never reading and critiquing the entire article. Nevertheless, these two studies were always being cited as evidence against the use of topical antibiotics.

In the study by Clayton et al, published in 1990, the authors compared the clinical efficacy of a topical gentamicin and topical aluminum acetate in 139 ears with otorrhea. At 21 days, efficacy rates among 102 evaluable ears were 68 and 67%, respectively--obviously not a statistically significant difference. No organisms resistant to aluminum acetate were seen at any point during the trial. By contrast, organisms resistant to gentamicin during in vitro testing (which is based on expected systemic, not topical, serum gentamicin levels achieved by recommended parenteral dosing) were seen in 12 patients at presentation, and another patient with P aeruginosa developed resistance during treatment. Based on these findings, the authors recommended that topical antiseptics such as aluminum acetate be used for the initial treatment of otorrhea on the grounds of cost, avoidance of resistance, and avoidance of ototoxicity. However, when we look more closely at this study, we see several serious flaws. First, the study was not specific for acute otitis externa; it included a heterogeneous collection of patients with otorrhea. Second, the dropout rate was 26%. Moreover, there was no mention of improvement in terms of time to clinical cure and no mention of adverse effects during treatment. Finally, as has already been mentioned, in the presence of a tympanic membrane perforation, aluminum acetate might be expected to be both painful and ototoxic.

The study by Tsikoudas et al, published in 2002, was a comparison of a steroid alone (n = 17) with an antibiotic/ steroid combination (n = 22) for 14 days for the treatment of acute otitis externa. Patients were assessed on days 3, 7, and 11. Efficacy was rated on the basis of each patient's documentation of symptoms at each visit, as well as the assessments of a blinded observer. At the day-11 visit, both patient and observer evaluations revealed no statistically significant differences between the two therapies. The authors concluded that topical aminoglycoside antibiotics convey no significant benefit in acute otitis externa. However, I believe we should consider this study as nothing more than a pilot project. Again, let's look at the limitations of this study.

First, the authors admitted that microbiologic cultures were not obtained, and it is possible that there was some bias in the distribution of pathogenic bacteria between the two groups. Second, the authors said that the minimum difference between the two groups that could be considered statistically significant at p < 0.05 would be 20%. However, this would require a minimum patient population of 250 patients in each arm. Also, the authors did not quantify the time to cure. Finally, we don't know what the outcomes would have been if an aminoglycoside other than neomycin had been used.

And yet these two studies were cited frequently during the formulation of recommendations that were supposedly based on good evidence.

Dr. Giles: We need a defined treatment plan for a patient with otitis externa. I think prescribing an antibiotic represents a better plan than having a patient undergo regular aural toilet in the office or in a home-care setting. I just don't think that works. There are very few people who can perform aural toilet well. But if we can get eardrops down into the bottom of the ear canal to the eardrum, there is no reason not to use an antibiotic and then follow it up with something for prevention, such as a 50/50 solution of alcohol and white vinegar--as long as the eardrum is intact. This is the approach I take, and I am certain that it is the approach a primary care physician should take.

The agent I prefer is the combination of a quinolone and a steroid. Several clinical trials have shown that antibiotics and steroids have a symbiotic relationship. (5,6) Also, steroids are known to shorten the time to cure by a day or two compared with placebo. That might not seem like much, but it is significant to a patient who is incapacitated by pain and unable to engage in regular daily activities.

References

(1.) van Asperen IA, de Rover CM, Schijven JF, et al. Risk of otitis externa after swimming in recreational fresh water lakes containing Pseudomonas aeruginosa. Br Med J 1995;311:1407-10.

(2.) Van Ginkel CJ, Bruintjes TD, Huizing EH. Allergy due to topical medications in chronic otitis externa and chronic otitis media. Clin Otolaryngol Allied Sci 1995;20:326-8.

(3.) Clayton MI, Osborne JE, Rutherford D, Rivron RR A double-blind, randomized, prospective trial of a topical antiseptic versus a topical antibiotic in the treatment of otorrhoea. Clin Otolaryngol Allied Sci 1990;15:7-10.

(4.) Tsikoudas A, Jasser R England RJ. Are topical antibiotics necessary in the management of otitis externa? Clin Otolaryngol Allied Sci 2002;27:260-2.

(5.) Pistorius B, Westberry K, Drehobl M, et al. Prospective, randomized, comparative trial of ciprofloxacin otic drops, with or without hydrocortisone, vs polymyxin B-neomycin-hydrocortisone otic suspension in the treatment of acute diffuse otitis externa. Infect Dis Clin Pract 1999;8:387-95.

(6.) Roland PS, Pien FD, Schultz CC, et al. Efficacy and safety of topical ciprofloxacin/dexamethasone versus neomycin/polymyxin B/hydrocortisone for otitis externa. Curr Med Res Opin 2004;20: 1175-83.

Debate between Billy Giles, MD, and John Rutka, MD, FRCSC