Optimized Ophthalmic: Advances in the Treatment of Ocular Diseases in Animals
Journal Title: Biomedical Journal of Scientific & Technical Research (BJSTR) - Year 2017, Vol 1, Issue 6
Abstract
The eye is a highly complex organ in terms of structure and function. It is a very sensitive organ, the function of which may be affected even with mild insult to its homeostasis, due to direct injury or due to other local or systemic diseases Scountzou [1]. The practice of ophthalmology, whether on humans or animals, can be reduced to the simple goal of getting the right pharmacological agent at the appropriate therapeutic dose to the target ocular tissue by a method that does not damage healthy tissue. In ocular disease, however, this simple goal becomes more challenging because of the highly sensitive ocular tissues (e.g., the uveal tract and retina) and the presence of tissue barriers to drug penetration, namely the lipophilic corneal epithelium, the hydrophilic corneal and sclera stroma, the conjunctival lymphatics, choroidal vasculature, and the blood-ocular barriers Weiner & Gilge [2]. There are only a few veterinary ocular drugs that have been approved for marketing by the US Food and Drug Administration (FDA) (e.g., topical antibiotics [triple antibiotic], corticosteroids [neopolydex], cyclosporine [0.2% Opt immune]). Most of the ocular medications veterinarians prescribe are those approved for human use, such as intraocular pressure (IOP) lowering medications, topical non steroidal anti-inflammatory drugs (NSAIDS), corticosteroids, etc. this approach has its limitations; it is wrong to assume that if a drug product works well in the human eye, it will work well in the animal eye and differences in eye anatomy and physiology of the animals encountered in veterinary practice, their unique diseases and specific responses to therapeutic agents are all sufficient reasons for encouraging and promoting research and development in veterinary ophthalmology Weiner [3]. Drug Delivery System Potential routes of administration of drugs for ocular (adnexal, ocular surface, intraocular or orbital) diseases include topically applied ointments, solutions, or suspensions; systemic (parenteral or oral) administration, local (subconjunctival, intracameral, intravitreal, sub retinal, retro bulbar) injections or controlled drug delivery (hydro gels, inserts and prodrugs) Maggs [4]. In clinical practice the anterior segment of the eye (cornea, conjunctiva, sclera, anterior uvea) can be treated with topical ocular eye drops, the most commonly used dosage form in ocular drug treatment. Unfortunately, the ophthalmic topical formulations bear some drawbacks related to poor ocular bioavailability due to many anatomical and physiological barriers existing in the eye Gunda et al. [5]. Drugs are mainly eliminated from the precorneal lacrimal fluid by solution drainage, lacrimation and nonproductive absorption to the conjunctiva of the eye Lee & Robinson [6]. These factors and the cornea1 barrier limit the penetration of the topically administered drug into the eye. The normal commercial eye dropper delivers a drop volume of 25-56 μl (average 39 μl) Lederer & Harold [7]. When an eyedrop is instilled, the cul-de-sac may momentarily contain a 30 μl volume, but the instilled solution is rapidly removed by spillage from the conjunctival sac or loss through the puncta to the lacrimal drainage system until the tears return to their normal volume. This rate decreases with viscosity and increases with larger eye drop volumes Lee & Robinson [8]. Ocular administration of irritating drugs or vehicles increases the drug loss from the precorneal area to a further extent due to induced lacrimation Lee & Robinson [6].An important route of drug loss from the lacrimal fluid is systemic absorption through the conjunctiva of the eye. Due to the relative leakiness of the membrane, rich blood flow and large surface area, conjunctival uptake of a topically applied drug from the tear fluids is typically an order of magnitude greater than cornea1 uptake Urtti [9].
Authors and Affiliations
KR Kurup, PV Parikh, JK Mahla, DA Ratnu
Keywords
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- EP ID EP573733
- DOI 10.26717/BJSTR.2017.01.000500
- Views 195
- Downloads 0
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