Other topical agents are safer and just as effective. (Rebuttal).

Certainly we must actively treat middle ear disease, especially when the tympanic membrane is perforated and the ear is discharging, because these conditions can lead to complications. But physicians should not be responsible for causing complications. Also, there are other issues that we must consider.

Aminoglycoside persistence

Although a short course with a topical aminoglycoside is probably safe, what do we do if multiple courses are required? Aran and colleagues performed an interesting study of systemic radiolabeled gentamicin in an animal model. (1) At 24 hours following administration, they were able to detect gentamicin in the outer hair cells. When they re-examined the animals 11 months later, they found that the drug was still in the outer hair cells (despite the fact that there was no apparent toxicity).

As we see from this study, gentamicin does not disappear. One dose might not cause toxicity over such an extended period, but ototoxicity could occur after repeated dosings because there might be a cumulative effect.

Genetic susceptibility

We are learning that certain groups of people around the world--specifically, those in the Far East and the Middle East--seem to be very sensitive to the effects of aminoglycosides. These patients have a mitochondrial mutation, and there is a risk that they might completely lose their hearing and vestibular function after only one or two doses. As people continue to travel and migrate all over the world, we might begin seeing more of these mutations in North America. So it behooves us to be careful in our choice of treatment in certain populations.

Safer alternatives

Other classes of drugs, particularly the fluoroquinolones, are safer than topical aminoglycosides. Even substances such as acetic acid can be harmful in animal models. To my knowledge, there is no report in the literature of quinolone-induced toxicity in the inner ear in humans. I see little reason to use an aminoglycoside when we have completely safe antibiotics that cover the same bacteria.

Medicolegal issues

Serious complications

Rightly or wrongly, lawyers will pursue litigation against a physician if an adverse effect occurs as a result of treatment for a discharging ear with a medication that is known to cause ototoxicity. Consequently, some coun tries have restricted their use to certain specific circumstances. The British Parliament passed legislation limiting the duration of topical aminoglycoside treatment to 7 days. Canadian health officials have forbidden the use of topical aminoglycosides in any ear that has a tympanic membrane perforation or that is discharging.

In summary, although topical aminoglycosides are certainly effective in the treatment of middle ear pathology, I find it difficult to support their continued use in light of their ototoxic potential and the availability of safer agents such as the quinolones, which cover the same pathogens and appear to be just as effective.

Perhaps the most disconcerting aspect of topical aminoglycoside ototoxicity is the risk of bilateral vestibular loss. The consequences of such a loss can be devastating; affected patients rarely recover enough to resume normal physical activity. In fact, some of these patients remain permanently wheelchair-bound, despite the best efforts of vestibular rehabilitation specialists. On Short Form 36 evaluations, patients with a bilateral vestibular loss scored 50% less than age- and sex-matched normal controls in five of eight quality-of-life categories, and they were well below the average in the other three. (The Short From 36 is a well-validated and reproducible method of measuring physical, emotional, social, mental, and other functions.) The disability in these patients can be so severe that it is likely they will seek large damage awards in court.

Reference

(1.) Aran JM. Current perspectives on inner ear toxicity. Otolaryngol Head Neck Surg 1995;1 12:133-44.