[In-vivo efficacy of a commercial ear antiseptic containing chlorhexidine and Tris-EDTA. A randomised, placebo-controlled, double-blinded comparative trial].

AIM: The important aspect of a successful therapy for otitis externa is cleaning of the external canal. Several cleaners are available for this purpose. In the light of increasing bacterial resistance against antibiotics a combined therapy with antiseptics is desirable. The aim of this study was to evaluate the efficacy of a cleaner containing chlorhexidine (1500µg/ml) and Tris-EDTA (48µg/ml) clinically, cytologically and microbiologically in a placebo-controlled double-blinded trial.

MATERIAL AND

METHODS

In 64 dogs ear cleaner (group A) or placebo (group B) was used twice daily followed by an ear medication containing marbofloxacin/dexamethasone/clotrimazole once daily. After 2 weeks patients were re-evaluated clinically and cytologically. In addition at the beginning and after 14 days an ear swab of each ear underwent a microbiological examination and sensitivity testing.

RESULTS

On cytology, there was a significant reduction in the count of cocci (p<0.0001), rods (p=0.007) and neutrophils (p=0.0001) in the treatment compared to the placebo group. Yeasts were significantly reduced in both groups (group A p<0.0001, group B p<0.001). Clinical examination did not reveal a significant difference between the two groups (p=0.59). The number of marbofloxacin-resistant bacteria increased in group A from 0 to 44% (p=0.0025) and in group B from 8 to 31% (p>0.05).

CONCLUSION

Chlorhexidine and Tris-EDTA in combination with marbofloxacin/dexamethasone/clotrimazole were effective in cytological reduction of bacteria in canine infectious otitis externa. The number of marbofloxacin-resistant bacteria increased significantly.

CLINICAL RELEVANCE: Based on this study, chlorhexidine and Tris-EDTA in combination with antimicrobial ear medication can be assumed to be recommended for the treatment of otitis externa complicated by bacterial infection to reduce bacteria, however the high risk of resistance development exists. Side effects are to be expected.