Effect of topical florfenicol, terbinafine and mometasone furoate ear drops on adrenocortical function in healthy small breed dogs with bilateral otitis externa

Abstract

Background Testing for hyperadrenocorticism is commonly pursued in adult dogs with dermatological disease, and adrenocortical suppression has been well‐documented following the use of topical corticosteroids in otic preparations. An otic suspension that contains florfenicol, terbinafine and mometasone furoate, and lasts for 30 days after a single application, frequently is used to treat canine otitis externa (OE). This medication was shown to cause adrenocortical suppression on Day (D)2 postadministration and two weeks after two applications two weeks apart. Hypothesis/objectives The objective of this study was to determine if topical florfenicol/terbinafine/mometasone furoate causes adrenocortical suppression in healthy, small‐breed dogs with bilateral OE at D28 postapplication. Animal Seven client‐owned dogs weighing <10 kg diagnosed with non‐Pseudomonas bilateral OE. Materials and methods Cortisol was measured pre‐ and post‐adrenocorticotropic (ACTH) stimulation on D0. Topical florfenicol/terbinafine/mometasone furoate was applied in both ears. Dogs were reassessed on D28, and cortisol was measured pre‐ and post‐ACTH stimulation. Results The median pre‐ and post‐ACTH cortisol concentrations on D28 were 2.5 µg/dL (range 2.0–5.0 µg/dL) and 14.3 µg/dL (range 11.5–23.1 µg/dL), respectively. There was no significant difference (P = 0.85) between post‐ACTH cortisol concentrations from D0 to D28. Conclusions and clinical relevance Results demonstrated no evidence of adrenocortical suppression, suggesting that there is no need to delay adrenocortical function testing in dogs treated with topical florfenicol/terbinafine/mometasone furoate when applied as per the manufacturer’s recommendations.

Pharmacology of drugs used in autoimmune dermatopathies in cats and dogs: A narrative review

“…If long-term usage of topical GC is needed as an adjunct therapy to maintain CR, topical mometasone furoate may be a safer long-term option as it has minimal effect on the adrenocortical function and low systemic availability. 192,193 Tacrolimus is a calcineurin inhibitor that inhibits Tcell activation. However, unlike CsA, tacrolimus binds to FK506 binding protein, which then suppresses the activation of the NFAT pathway and inhibits early activation of T cells.…”

“…topical tacrolimus) can be considered. If long‐term usage of topical GC is needed as an adjunct therapy to maintain CR, topical mometasone furoate may be a safer long‐term option as it has minimal effect on the adrenocortical function and low systemic availability 192,193 …”