Advanced Drug Delivery Systems: Ophthalmic Preparations

Vocabulary practice flashcards covering ocular drug delivery forms, ocular anatomy and physiology, drug loss and absorption kinetics, insert technologies, contact lenses, and packaging requirements.

Ophthalmic Drug Delivery Systems

Sterile preparations essentially free from foreign particles, compounded and packaged for instillation into the eye to treat ocular surface or intraocular conditions.

Miotics

Ophthalmic pharmacological agents that cause constriction of the pupil, exemplified by pilocarpine hydrochloride.

Mydriatics

Ophthalmic pharmacological agents that cause dilation of the pupil, exemplified by atropine.

Sclera

The protective outer fibrous layer of the human eye, commonly referred to as the white of the eye.

Iris

The pigmented muscular ocular tissue that responds to ambient light intensity by adjusting the diameter and size of the pupil.

Crystalline Lens

A transparent, biconvex internal structure of the eye responsible for focusing incoming light onto the retina.

Cornea

The transparent anterior continuation of the sclera that allows light penetration and supplies a major portion of the eye's refractive focusing power.

Conjunctiva

A thin, vascularized, transparent mucous membrane that lines the interior of the eyelids and covers the visible surface of the sclera.

Choroid

The vascular layer located between the sclera and the retina that supplies blood and nutrients to ocular structures.

Retina

The innermost photoreceptive layer of the eye that converts light images into electrical signals conveyed via the optic nerve to the brain.

Aqueous Humor

A clear, watery fluid filling the anterior chamber of the eye between the cornea and the lens.

Vitreous Humor

A clear, colorless gelatinous mass that fills the posterior cavity of the eye behind the crystalline lens.

Precorneal Tear Capacity

The normal physiological fluid capacity of the tear sac, which measures $10\text{–}30\,\mu\text{l}$; instillation beyond $30\,\mu\text{l}$ triggers rapid dose loss via overflow.

Nasolacrimal Canal Drainage

The physiological drainage route of instilled ocular solutions into the tear ducts and gastrointestinal tract, causing bitter or salty sensations and potential systemic absorption.

Transcorneal Absorption

The primary pathway of intraocular drug transport requiring dual solubility to traverse both the lipophilic corneal epithelium and the hydrophilic stroma into the aqueous humor.

Ophthalmic Solutions

Sterile, particulate-free liquid preparations containing completely dissolved active drugs, characterized by high dosing uniformity but short corneal residence time.

Ophthalmic Suspensions

Sterile liquid preparations consisting of micronized insoluble drug particles dispersed in a liquid vehicle to prevent corneal scratching and prolong drug dissolution.

Ophthalmic Powders for Reconstitution

Sterile lyophilized solid drug preparations packaged separately from the reconstitution vehicle to ensure chemical stability and extended shelf life.

Gel-Forming Solutions (In Situ Gels)

Liquid ocular formulations that remain liquid in their container and undergo phase transition into a viscous gel upon contacting physiological tear fluid.

Cellulose Acetate Phthalate

A pH-sensitive in situ gelling polymer that maintains liquid form at pH $4.5$ and undergoes sol-to-gel transition at the tear fluid pH of $7.4$.

Timolol GFS

A commercial gel-forming solution of timolol maleate that extends intraocular pressure-lowering efficacy from $12\,\text{hours}$ to $24\,\text{hours}$, permitting once-daily administration.

Ophthalmic Ointments

Semisolid sterile preparations packed in collapsible tubes of $3\text{–}5\,\text{g}$ that soften at ocular temperature to enhance contact time, predominantly administered at bedtime due to causing blurred vision.

Nonerodible Ocular Inserts

Insoluble, flexible solid drug delivery devices placed in the conjunctival cul-de-sac to deliver medication at a controlled steady state without dissolving.

Ocusert

A nonerodible ocular insert containing a pilocarpine reservoir enclosed by rate-controlling copolymer membranes and a white annular ring, delivering drug for $1\,\text{week}$ to treat glaucoma.

Soluble Ocular Inserts

Biodegradable solid ocular devices compounded with erodible matrices (such as hydroxypropyl cellulose or carbomer) that completely dissolve within $12\text{–}24\,\text{hours}$, precluding removal.

Lacrisert

A sterile, translucent, rod-shaped soluble insert composed of hydroxypropyl cellulose (HPC) that dissolves in $12\text{–}24\,\text{hours}$ to stabilize and thicken the precorneal tear film in dry eye syndrome.

Rigid Contact Lenses

Durable, low-cost optical or therapeutic discs fabricated from polymethyl-methacrylate (PMMA) that require an adaptation period and may cause corneal scratching.

Soft Contact Lenses

Flexible and immediately comfortable corneal discs manufactured from hydrophilic hydrogels such as hydroxyethylmethyl-methacrylate (HEMA).

Soaking Solutions

Contact lens maintenance liquids formulated with antimicrobials such as chlorhexidine gluconate, benzalkonium chloride, or cetylpyridinium chloride to store and hydrate hard lenses.

Artificial Tears (Rewetting Solutions)

Formulations containing polymers such as polyvinyl alcohol or Tween 80 formulated to rewet contact lenses in situ and augment the physiological tear film.

ABAK System

A preservative-free multidose delivery container incorporating a $0.2\,\mu\text{m}$ microporous membrane filter that delivers calibrated, unpreserved sterile eye drops.