Drugs Ocular Therapeutic

Some ophthalmic drugs produce blurring of vision, which can result in falls and other injuries. The nurse warns patients to exercise care when getting out of bed when the vision is impaired by these drugp. Patients using the pilocarpine ocular therapeutic system must have the system replaced every 7 days (see Chap. 24). The system is inserted at bedtime because myopia (nearsightedness) occurs for several hours after insertion. 

The Ocusert Pilo-20 and Pilo-40 Ocular Therapeutic System is an elliptical membrane that is soft and flexible and designed to be placed in the inferior cul-de-sac between the sclera and the eyelid and to release pilocarpine continuously at a steady rate for 7 days. The design of the dosage form is described by Alza in terms of an open-looped therapeutic system, having three major components (a) the drug, (b) a... 

J. C. Lang and M. M. Stiemke, Biological barriers to ocular delivery in Ocular Therapeutics and Drug Delivery, A Multidisciplinary Approach (I. K. Reddy, ed.), Technomic Publishing Company, 1996, pp. 51-132. 

Sustained delivery of ophthalmic medications is a novel approach in treating chronic intraocular infections in conditions where systemic administration is accompanied by undesirable side-effects and repeated intravitreal injections carry the risk of infection. The administration of medications by implants or depot devices is a very rapidly developing technology in ocular therapeutics. The various types of implant and mechanisms of drug release have been discussed in general in Chapter 4. 

Eggers HM.Toxicity of drugs used in diagnosis and treatment of strabismus. In Srinivasan DB, ed. Ocular therapeutics. New York Masson, 1980 115-122 Chapter 15. 

Hutak, C. M., and R. B. Jacaruso. 1996. Evaluation of primary ocular irritation Alternatives to the Draize test. In Ocular therapeutics and drug delivery, edited by I. K. Reddy. Lancaster, Penn., USA Tech-nomic Publishing Company, pp. 489-525. 

PHARMACOKINETICS AND TOXICOLOGY OF OCULAR THERAPEUTIC AGENTS Drug Delivery Strategies... 

Bloquel, C., Bourges, J. L., Touchard, E., Berdugo, M., BenEzra, D., Behar-Cohen, F. (2006). Non-viral ocular gene therapy potential ocular therapeutic avenues. Adv Drug Deliv Rev 58, 1224-1242. 

Drug delivery in ocular therapeutics is a challenging problem and is a subject of interest to scientists working in the multidisciplinary areas pertaining to the eye. 

A. Zaffaroni, Selective Administration of Drug with Ocular Therapeutic System, U.S. Pat. 4,186,184 (Jan 29, 1980) to Alza Corp. through Chem. Abstr. 92 185937b (1980). 

The latter device, developed by Alza Corp., Palo Alto, California, is a diffusion unit consisting of a drug reservoir (e.g., pilocarpine HCl in an alginate gel) enclosed by two release-controlling membranes made of ethylene-vinyl acetate copolymer, and enclosed by a white ring which Slows positioning of the system in the eye. The Pilo-20 Ocular Therapeutic System has a release rate of 20 mg/hr for 7 days, and the Pilo-40 system a release rate of 40 mg/hr for 7 days. The former releases a total of 3.4 mg in 7 days, the latter 6.7 mg. In order to maintain constant release of tog, and in accordance with the principles of diffusion, there... 

One-week-duration OCUSERT ocular therapeutic systems (Figure 2) in the form of a thin, elliptical film, worn beneath the eyelid, for delivery of the antiglaucoma drug pilocarpine (9,10) (an alternative to taking the drug in eyedrops). 

The conventional concentration of benzalkonium chloride in eyedrops is 0.01%, with a range of 0.004-0.02% [111]. While uptake of benzalkonium chloride itself into ocular tissues is limited [113], even lower concentrations of benzalkonium chloride have been reported to enhance corneal penetration of other compounds including therapeutic agents [93,112,114]. The differential effect of this preservative on the cornea compared to the conjunctiva can be exploited to target a drug for corneal absorption and delivery to the posterior segment of the eye [115]. Its use has been proposed as a means of delivering systemic doses by an ocular route of administration [116]. 

Topical application is the most common route of administration for ophthalmic drugs. Advantages include convenience, simplicity, noninvasive nature, and the ability of the patient to self-administer. Because of blood and aqueous losses of drug, topical medications typically do not penetrate in useful concentrations to posterior ocular structures and therefore are of no therapeutic benefit for diseases of the retina, optic nerve, and other posterior segment structures. 

Anterior uveitis and neutropenia are fairly common side effects of cidofovir therapy. Ocular hypotony and metabolic acidosis are rare. Exposure to therapeutic levels of cidofovir causes cancer in rats therefore, this drug should be considered a potential human carcinogen. Animal studies have also shown cidofovir to produce embryotoxic and teratogenic effects and to impair fertility. 

Nevertheless, very limited research has been carried out to develop DDS for the posterior segment of the eye in the last decades. Whereas new antiangiogenic compounds and neurotrophic factors can open new therapeutic avenues in the treatment of AMD, retinal dystrophies and ocular manifestations of diabetes, the frequent intraocular injections of these compounds remain a problem and are associated with complications and discomfort for the patient. Thus, the need for efficient noninvasive DDS for the administration of drugs to the back of the eye is awaiting a ground-breaking multidiscipline advancement. 

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