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Pharmacological particulars
Pharmacotherapeutic group: Otologicals – Corticosteroids and anti-infectives in combination.
ATC-vet code: QS02CA90
Pharmacodynamic properties
The veterinary medicinal product is a fixed combination of three active substances (corticosteroid, antifungal and antibiotic):
Betamethasone acetate belongs to the diesters class of the glucocorticosteroids with a potent intrinsic glucocorticoid activity which relieves both inflammation and pruritus leading to an improvement of clinical signs observed in otitis externa.
Terbinafine is an allylamine with a pronounced fungicidal activity. It selectively inhibits the early synthesis of ergosterol, which is an essential component of the membrane of yeasts and fungi including Malassezia pachydermatis (MIC90 of 2 µg/ml). Terbinafine has a different mode of action than azole antifungals, therefore there is no cross resistance with azole antifungals.
Florfenicol is a bacteriostatic antibiotic which acts by inhibiting protein synthesis. Its spectrum of activity includes Gram-positive and Gram-negative bacteria including Staphylococcus pseudintermedius (MIC90 of 8 µg/ml).
Due to the high antimicrobial concentrations achieved in the ear canal and the multifactorial nature of otitis externa, in vitro susceptibility may not be directly correlated with clinical success.
Pharmacokinetic properties
The formulation dissolves in ear wax and is slowly eliminated from the ear mechanically.
Systemic absorption of all active substances was determined in multiple-dose studies after placing the veterinary medicinal product into both ear canals of healthy mixed breed dogs. Absorption occurred primarily during the first two to four days after administration, with low plasma concentrations (1-42 ng/ml) of active substances.
The extent of percutaneous absorption of topical medications is determined by many factors including the integrity of the epidermal barrier. Inflammation can increase the percutaneous absorption of veterinary medicinal products.