Routes of Administration and Drug Delivery Systems in Ophthalmology
For ocular drugs to be effective an ideal drug delivery system (DDS) should deliver the drug at the receptor site in ocular tissues in relatively high concentration to elicit the desired pharmacological response. Most of the ophthalmic drugs are applied topically in the form of eye drops.
The time course of drug deliver from an eye drop follows a first order kinetics. It is well known that about 1% or less of an applied dose is absorbed across the cornea topically to reach the anterior segment of eye.
The major problem in the drug treatment (topical) of ocular diseases is the difficulty of achieving a sufficient quantity of drug at the desired site of action. The tight junctions of Iris Capillaries and Retina act as a barrier to the diffusion of drugs from the blood into the aqueous and vitreous and the cornea acts as a barrier to drugs applied locally.
Another factor quite important is the rate of removal from the eye of any drug that does actually penetrate into the aqueous or vitreous because although inflammation may reduce the barrier to penetration of the drug into the eye, the associated hypraemia will also speed the removal of the drug from the eye.
During the last decade research is going on in Ophthalmic field for a suitable mode of Ocular therapy to provide higher and sustained penetration of the drugs into the Ocular tissues and anterior chamber promptly and effectively. Most important factor which modify drug penetration is slow release of the drug thereby increasing the contact time of the drug to the Ocular structures. The duration of drug action in the eye can be extended by
a. Reducing drainage through the use of viscosity enhancing agents.
b. Improving corneal drug penetration. An ideal drug
delivery system should have
(i) Spatial placement
(ii)Controlled drug delivery.
The route of administration are local and systemic for ocular diseases.
OPTOMETRY-SHARP VISION
Optometrist