Pharmacology of Otic Medication PDF

PHARMACOLOGY OF OTIC PRODUCTS Pharmacology and therapeutics II Integrated Master in Veterinary Medicine 2024-25 Ana Oliveira, MV, MsC, Dip ECVD, PhD EBVS European Specialist in Veterinary Dermatology Anatomy of the ear The ear consists of three major parts; the outer, middle, and inner ear. The...

PHARMACOLOGY OF OTIC PRODUCTS Pharmacology and therapeutics II Integrated Master in Veterinary Medicine 2024-25 Ana Oliveira, MV, MsC, Dip ECVD, PhD EBVS European Specialist in Veterinary Dermatology Anatomy of the ear The ear consists of three major parts; the outer, middle, and inner ear. The outer ear includes the pinna and the ear canal. The ear canal carries sound to the tympanic membrane (ear drum). The shape of the ear canal is “L” shaped and where cerumen and other secretions accumulate. (Martini-Johnson, 2022) Anatomy of the ear The middle ear includes the tympanic membrane, auditory ossicles (bones that transmit and amplify air vibrations), and eustachian tube. The inner ear includes the cochlea and vestibular apparatus. (Martini-Johnson, 2022) Anatomy of the ear The cochlea is responsible for the hearing. The vestibular system is responsible for the balance. ANATOMY OF THE EAR CANAL OTITis EXTERNA External ear canal ◼ Pruritus itching inside or around the ear. ◼ Pain ◼ Inflammation ◼ Shake the head ◼ Excess of cerumen ◼ Change of the smell TYPES OF MEDICATION USED IN EAR CANAL ◼ Ear canal cleaners ◼ Medication to treat otitis CHARACTERISTICS OF THE EAR CANAL CLEANER ◼ To clean the ear canal we can use: ceruminolytics and surfactants agents. ◼ Surfactants emulsify debris, breaking it up and keeping it in solution. ◼ Astringents dry the ear canal surface, preventing maceration. ◼ Maintaining a low pH and incorporating antimicrobial agents can inhibit microbial proliferation CHARACTERISTICS OF THE EAR CANAL CLEANER ◼ Ear cleaners can be ototoxic. ◼ Water, saline or squalene are particularly appropriate for cases with ruptured tympanic membranes as many other compounds are potentially ototoxic. these one are safe even if tympanic membrane are damaged CERUMINOLYTICS Ceruminolytics are organic oils and solvents (e.g. propylene glycol, lanolin, glycerine, squalane, butylated hydroxytoluene, cocamidopropyl betaine and mineral oils) commonly included in ear cleaners to soften and dissolve cerumen. They are of most use in mildly waxy or dirty ears and are relatively safe for routine at-home cleaning if the tympanic membrane is intact. It is, however, questionable if they are of much benefit in ears with a purulent discharge. Squalene is safe to use in case of rupture ear drum. Pictures from the author SURFACTANTS Surfactants are effective with both ceruminous and purulent debris. Surfactants help expedite the cleaning process by emulsifying debris, breaking it up and keeping it in solution. Some detergents can be irritating, particularly to the middle ear mucosa, and are contraindicated if the tympanic membrane is ruptured. Useful surfactants include dioctyl sodium sulfosuccinate (DSS or docusate), calcium sulfosuccinate and other detergents. FOAMING AGENTS Foaming agents such as urea and carbamide peroxides release oxygen in situ. This helps disperse debris and aerates the ear canals. The foaming action causes anxiety in some animals though. Not available in all countries. Dr. Guibaldo ADSTRINGENTS Astringents dry the ear canal surface, to prevent maceration. They are often combined with ceruminolytics and surfactants in cleaning/drying products, but can also be used separately after ear cleaning or prophylactically after bathing or swimming in dogs that are prone to otitis. Commonly employed astringents include isopropyl alcohol, boric acid, benzoic acid, salicylic acid, sulfur, aluminium acetate and silicon dioxide. ANTIMICROBIAL EFFECT Antimicrobial compounds are frequently incorporated in ear cleaners to retard microbial proliferation. An ear cleaner containing parachlorometaxylenol (PCMX) (Epi-Otic®) has potent in vitro and in vivo activity against Pseudomonas aeruginosa, Staphylococcus intermedius and Malassezia pachydermatis. Chlorhexidine (1–3%) is also active against Staphylococcus intermedius and Malassezia pachydermatis, but is less active against Pseudomonas.Solutions that maintain a low pH are also antimicrobial. CONTRAINDICATIONS AND SIDE-EFFECTS Some cleaning fluids may provoke inflammatory reactions, especially if introduced into the middle ear. Experimental inoculation of propylene glycol, DSS, carbamide peroxide and triethanolamine initiated inflammatory changes to the middle ear mucosa of normal dogs and guinea pigs, whereas squalane had no effect. CONTRAINDICATIONS AND SIDE-EFFECTS: CHLORHEXIDINE Chlorhexidine is often regarded as ototoxic although experimental infusion at a concentration of 0.05% into normal canine ears caused no ill effects, whereas infusion of a 2% solution did cause ototoxicity. In these experiments, however, the compounds were directly inoculated into normal bullae without flushing and the effect in inflamed ears when combined with other cleaning techniques is unknown. In a study designed to simulate a clinical situation no vestibular or cochlear abnormalities were seen when 0.2% chlorhexidine was placed in the external ear canal of dogs with ruptured tympanic membranes. Nevertheless, in the absence of firm information about the integrity of the tympanic membranes caution should be exercised. How to clean the ear canal The veterinary technician demonstrated to the owner how to properly clean the ears using the following steps: Gently pull the earflap up and slightly back with one hand. Using the other hand, apply a small amount of medication at the entrance of the ear canal and wait a few seconds for the medication to run down into the ear canal. Put one finger in back of and at the base of the ear and your thumb in front. Gently massage the ear canal between your finger and thumb.You may hear a squishing sound; this tells you that the medication went into the horizontal ear canal. Release the ear and let your dog shake its head. You should then clean the outer part of the ear canal and the inside of the earflap with a swab.. Do not use cotton tipped applicators to do this, as they tend to push debris back into the vertical ear canal and you may cause damage to the ear. GENERAL PHARMACOLOGY FOR INFECTIOUS OTITIS ◼ Most of the products are composed of an antibiotic, antifungal and a glucocorticoid. ◼ Can be used against bacterial and Malassezia otitis TOPICAL ANTIBIOTICS ◼ Fluoroquinolones: ◼ Enrofloxacin ◼ Orbifloxacin ◼ Marbofloxacin ◼ Aminoglycosides: ◼ Gentamycin ◼ Amicacin ◼ Neomycin ◼ Tobramycin ◼ Large spectrum pennicillins ◼ Polimixina B. ANTIMYCOTICS AGAINST MALASSEZIA ◼ Topical antimycotic are very effective ◼ Miconazole, clotrimazole, posaconazole and nistatin.  OTOTOXICITY ◼ Ototoxic drugs: ◼ Polimyxin B, tobramycin and neomycin. ◼ Potentially safe: ◼ Gentamycin and amicacyin ? ◼ Ototoxicity depends on the formulation and presence of tympanic membrane. ◼ Seguros: ◼ Fluoroquinolones ◼ Antifungals ◼ The vehicle of the preparation can be ototoxic.