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Otitis externa — the place for polypharmacy a
J.M. Evans & Janet E. Jemmett
Veterinary Advisory Department , Glaxo Industries Limited Greenford , Middlesex, England Published online: 23 Feb 2011.
To cite this article: J.M. Evans & Janet E. Jemmett (1978) Otitis externa — the place for polypharmacy, New Zealand Veterinary Journal, 26:11, 280-283, DOI: 10.1080/00480169.1978.34567 To link to this article: http://dx.doi.org/10.1080/00480169.1978.34567
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NEW ZEALAND VETERINARY JOURNAL
Otitis externa - The place for polypharmacy J. M. Evans* and Janet E. Jemmett*
Downloaded by [UQ Library] at 05:06 01 February 2015
N.z. Vel. J. 26280-3
The aetiology of otitis externa is complex and several factors are involved, either as primary initiating causes or as secondary complications. In many cases, the condition is brought about by a combination of events, resulting in dynamic changes in the physiological, anatomical and microbiological state of the ear. Thus, identification of the cause in a particular case is very often impossible, impractical, or too time-consuming. Furthermore, the expense of bacteriological investigations may not be justified because the findings can be very difficult to interpret. Therefore, there are many occasions when a combination of therapeutic agents in one preparation - polypharmacy - would be advantageous as a first-line treatment. It is important, indeed fundamental, that such a medicament should be effective against all the common aetiological factors. Ideally, an antibiotic, an antifungal, a parasiticidal and an anti-inflammatory agent should be included. The results obtained in a clinical trial with a combined preparation that met the above requirements have shown that this approach to therapy is efficacious.
Otitis externa is a broad term, indicating an inflammatory process in the external auditory canal. This canal in dogs and cats is divided into a long vertical section and a relatively short horizontal one, separated by a right-angled bend. A full examination requires inspection of the canal past this bend right down to the ear drum. In painful cases or with fractious animals this calls for general anaesthesia. Two main categories of otitis externa are recognised: acute and chronic. We have established that the pathological changes are dynamic, resulting from a vicious circle of events.
The proper objective of a veterinary clinician is to treat disease in animals in such a way that the condition is resolved as rapidly as possible with minimal medication, interference and druginduced side effects. To achieve this necessitates, for most diseases, specificity of diagnosis and the prescription of a specific, proved treatment. However, there are situations in which that straightforward approach is not possible. For these, a combination of active substances may be needed in order to achieve the desired result: in other words, the clinician may need to practice polypharmacy. Our conviction is that a great number of cases of otitis ex tern a in dogs and cats fall into this category. Surveys have shown that about 500,000 dogs and cats are treated for otitis externa each year by veterinarians in the UK alone(l). Not surprisingly, therefore, the majority of veterinarians are familiar with the condition and their opinions in regard to the efficacy ofthis or that method oftreatment vary widely and often vehemently. For example, some veterinarians favour syringing: others never. Some favour powders while others condemn these out of hand. Some perform several aural resections a week, whereas others contend that the operation is seldom necessary. There seems no regional basis for these differing views; they are held by individuals and are based partly on what they were taught at COllege but, more importantly, on what each has learnt subsequently by trial and error. Likewise, many of the views expressed in this paper may be equally individual and even controversial.
AETIOLOGICAL FACTORS (Fig. 1)
(a) Skin Diseases. The integument, or lining, of the ear canal is an extension of the skin. Therefore, it can be involved in generalised skin diseases. This type of otitis is reported to be relatively frequent(J)(IO). (b) Trauma and Foreign Bodies. Trauma is a general term covering several factors that may lead to a damaged integument and initiate inflammation. Excess wax, soap, irritant medication and even plain water may induce inflammation. Foreign bodies like grass awns, or detritus, may directly induce inflammation. (c) Allergy. Inflammation due to allergic response may be a local reaction or, like skin disease, it may be part of a generalised problem. A 10% incidence due to an allergy has been reported(IO). (d) Mites (Otodectes cynotis). In cats, mite infestation is the commonest cause of otitis. In adult cats, the otitis is usually mild and, once treated, the animals seem to become resisAllergy
Mites Ear conformation
~ Excess hair Skin disease ---_~ Initiation ...- - - - Trauma
Fig. I. The