Systemic Antimicrobials

Systemic antibiotic therapy is appropriate when topical therapy is impossible, such as in a Cocker Spaniel with stenotic ear canals. When topical therapy of otitis media fails, it is usually the result of inability of the antibiotic to get to the bacteria.¹⁷ There may be sequestration of bacteria within folds or pockets of granulation tissue, which therefore remain unexposed to the topical antibiotic.

Oral fluoroquinolones often are sufficient for non-pseudomonal gram-negative middle ear infections.¹⁶ Because fluoroquinolone efficacy is based on a peak blood level, what level can be achieved and for what period should be determined. This is a dose-dependent antibiotic. Other antibiotics are time dependent. Their levels need to be constant to treat a bacterial infection, so the dose and the interval of dosing are crucial. When systemic time-dependent antibiotic therapy is required to treat resis­tant infections, it often requires the use of intravenous drugs. Ticarcillin-clavulanic acid (Timentin, Smith Kline, Beecham) has been reported as effective in treating multidrug resistant Pseudomonas otitis media in dogs when used as an intravenous injection of 15 to 25 mg/kg given three times daily.¹⁸ In human medicine, intra­venous ceftazidime has been used successfully for resistant Pseudomonas infections of the middle ear.