Preliminary study of the stability of dexamethasone when added to commercial veterinary ear cleaners over a 90 day period

The stability and in vitro antibacterial efficacy of enrofloxacin and gentamicin solutions against Staphylococcus pseudintermedius over 28 days

BACKGROUND

Many clinicians prepare compounded otic solutions to treat otitis externa (OE). Research evaluating the stability and antimicrobial efficacy of these solutions is limited.

HYPOTHESIS/OBJECTIVES

This study determined the chemical stability and in vitro bactericidal efficacy of compounded solutions of enrofloxacin and gentamicin during storage for 28 days.

MATERIALS AND METHODS

Solutions of enrofloxacin (10 mg/mL, 1%) and gentamicin (3 mg/mL, 0.3%) were prepared with normal saline and 1 mg/mL dexamethasone. Solutions were stored at room temperature (25°C) for 0, 14 and 28 days. The chemical stability of the antibiotics and dexamethasone were determined using liquid chromatography tandem mass spectrometry in triplicate. Efficacy assessment was made with 10 isolates of Staphylococcus pseudintermedius obtained from dogs with OE. Serial 10-fold dilutions of the bacteria with the compounded solutions were prepared and the colony count results were converted into colony-forming units (cfus). The mean cfu/mL and cfu/mL reduction rates were compared between Day (D)0, D14 and D28. All of the antimicrobial testing solutions were performed in triplicate.

RESULTS

Chromatography showed that both antibiotics and dexamethasone were stable for 28 days. No significant differences were observed in the antibiotic bactericidal efficacy of stored solutions at D0, D14 or D28.

CONCLUSIONS AND CLINICAL RELEVANCE

Solutions of 1% enrofloxacin and 0.3% gentamicin in normal saline with 0.1% dexamethasone maintained chemical stability and bactericidal efficacy over 28 days. These solutions can be considered as alternatives to commercial preparations for treatment of canine OE when indicated.

Stability of dexamethasone sodium phosphate over a 28 day period when added to commercial veterinary wipe and pad products

Background - Topical glucocorticoids commonly are used in the management of canine atopic dermatitis to control and prevent allergy flares. Compounding commercial veterinary wipe/pad products to include dexamethasone sodium phosphate (Dex SP) can simplify treatment protocols for owners. Dex SP has not been evaluated for stability when added to wipes/pads. Hypothesis/objective - To evaluate the stability of Dex SP when compounded in three commercial veterinary wipe/pad products containing chlorhexidine. Methods and materials - Dex SP (Dexium, Bimeda; Oakbrook Terrace, IL, USA) was added to TrizCHLOR 4 wipes (TCL; Dechra Veterinary Products; Overland Park, KS, USA), KetoHex wipes (KH; VetOne; Boise, ID, USA), and DOUXO Chlorhexidine Pads (DCP; Ceva Animal Health; Lenexa, KS, USA), creating a 0.04% Dex SP solution. The concentration of Dex SP was measured in μg/mL/wipe or pad in triplicate at Day (D)0, D14 and D28 using liquid chromatography with tandem mass spectrometry. The amount of Dex SP at baseline (D0) was compared to the amount recovered at D14 and D28. Results - The amount of Dex SP in TCL and KH was unchanged between D0, D14 and D28. The amount of Dex SP recovered from DCP on D0 (mean 89.40 μg/mL/pad), D14 (mean 65.58 μg/mL/pad) and D28 (mean 68.09 μg/mL/pad) revealed a significant decline from D0 to D14 (P = 0.004). Conclusions and clinical importance - These data provide evidence that Dex SP is stable for 28 days in TCL and KH, and not in DCP from D0 to D14 or D28 days.