Ophthalmic therapeutics Administration, drugs

General considerations in topical ophthalmic drug therapy Proper administration is essential to optimal therapeutic response. In many instances, health professionals may be too casual when instructing patients on proper use of ophthalmics. The administration technique used often determines drug safety and efficacy. 

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. 

Emulsions have been used for centuries for the oral administration of medical oils and vitamins and as dermatological vehicles. Recently, their application has been extended as drug carriers in the delivery and targeting of ophthalmic drags. An indomethacin emulsion has been reported to increase ocular bioavailability and efficacy compared to commercially available formulation in rabbits. 0.4% indomethacin emulsion showed 2.2 fold increase in the area under the anterior aqueous drag concentration/time curve compared to a 1% indomethacin suspension. The emulsion formulation also reduced ocular surface irritation caused by indomethacin Similar advantages have been shown for a pilocarpine emulsion which produced a prolonged therapeutic effect in comparison with pilocarpine hydrochloride eyedrops in man. It can be administered only twice a day, rather than four times daily for conventional formulation. 

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. 

Therapeutic uses An ophthalmic ointment of the drug is used topically in the eye for the chronic treatment of open-angle glaucoma. The effects may last for up to one week after a single administration. [Note Echothiophate [ek oe THI oh fate] is a newer drug that covalently bonds to acetylcholinesterase. Its use is the same as isoflurophate.]... 

The compounds described here are those commonly used as anti-ChE drugs and ChE reactivators in the U.S. Ophthalmic preparations are described in Chapter 63. Conventional dosages and routes of administration are given in the discussion of therapeutic applications. 

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