Permeability of Otowicks and Bacterial Penetration

Abstract

Objectives:

Otowicks are used to treat otitis externa with significant ear canal oedema. They ensure close contact between administered drops and the canal skin. How well drops penetrate through to reach the deep canal has not been accurately investigated. This in vitro study aims to investigate: (1) the permeability of otowicks to commonly used ear drops; (2) The ability of bacteria to penetrate through the otowick.

Methods:

Sterile otowicks were inserted into mock ear canals fabricated from plastic pipettes. These were held vertically over pseudomonas-seeded agar plates while Gentisone HC or CiloxinTM drops were administered; 4 drops, TDS for 5 days. Time taken for the drops to penetrate through the otowick was recorded. Separately, pseudomonas-seeded otowicks were inserted into plastic pipettes and treated with saline or antibacterial drops. The penetrating drops were observed for bacterial growth on sterile agar.

Results:

It took 6-8 drops before penetration occurred for both ear drops. Thereafter, otowicks treated with Ciloxan showed delayed penetration after 5 days (60-240 seconds) when compared with Gentisone (50-91 seconds). When sterile saline drops were applied to bacterially-contaminated otowicks, the penetrating drops displayed bacterial growth on agar, indicating that pseudomonas penetrated through the otowicks. However, when Gentasone or Ciloxan were applied, penetrating drops showed no bacteria growth on the corresponding agar plate.

Conclusions:

Bacteria can penetrate otowicks but this can be prevented by continuous application of antibacterial ear drops. Ear wicks need priming with 8 drops before starting a regime as the initial dose is fully absorbed by the otowick.