Author: D. N. CARLOTTI ,H. GATTO
Topical therapy (locally acting), animal dermatological conditions, formulations are available for the prescribing veterinary surgeon: shampoo, lotion, spray, ointment, cream, milk and gel, veterinary dermatologists , shampoo can be used in a limited area (eg chin, feet, dorsolumbar, ventral areas), cleansing and therapeutical properties, all over the body surface of a dog or a cat for treating generalized conditions, allow the active ingredients to be properly absorbed and reach adequate levels in the deep cellular layers, efficacy of shampoos on skin hydration, the surface lipid film and stratum corneum (interesting in case of keratoseborrhoeic disorders) can be evaluated objectively using a variety of techniques : transepidermal water loss (TEWL) measurement, corneocyte counts, measurement of corneal layer thickness, stripping, chemical analysis of lipid film, water content measurement, surface biopsies and corneometry, topical formulations, especially in prolonging the action of active ingredients applied to the skin. Microencapsulation (multilamellar microvesicles, liposomes, spherulites) increases bioavailability of therapeutic agents and promotes immediate and residual moisturising properties. Active agents are released from liposomes by membrane rupture. Spherulite surfactants are amphiphilic (two antagonistic extremities one hydrophilic, the other hydrophobic). They unit to form lamellar phases and are arranged in concentric layers according to a specific manufacturing process. They are multilamellar, each membrane acting as a diffusion barrier to reduce loss of active ingredients to the external environment. They can act as a vehicle for a great number of active agents, hydrophilic or hydrophobic (lipophilic), released continuously and progressively at the surface of hairs and skin. This surfactant formulation is very useful in dermatology because it allows hydrophilic, active ingredients access to an oily environment and conversely hydrophobic, active ingredients access to an aquatic medium. The type of surfactant varies. In some cases (cationic surfactants), their charge is positive and spherulites attach preferentially to hairs and skin, whilst in other cases (non-ionic surfactants), the charge is neutral, allowing spherulites to penetrate the deeper skin layers. A study has demonstrated that non-ionic spherulites can penetrate the epidermis, hair follicules, sebaceous glands and dermis, veterinary formulation (micro-emulsion, medicated shampoos.
