Ophthalmic Lecture Flashcards
What is a topical dosage form?
Instilled onto the external surface of the eye
What is a intraocular dosage form?
Administer by injection inside the eye
What is periocular dosage form?
Adjacent to the eye
What is intraocularly implanted mean?
Implanted as a ophthalmic device
What are drugs that are used in the eye?
Anti-glaucoma drugs Mydriatics & Cycloplegics Anti-inflammatory Anti-infectives Surgical adjuncts Diagnostic drugs Topical anesthetics Protectants & artificial tears
What is an example of anti-glaucoma drugs?
Pilocarpine HCl
What is an example of mydriatics & cycloplegics?
atropine
What is an example of anti-inflammatories?
Corticosteroids
What are the three types of anti-infectives and an example?
Antibiotics and antimicrobial agents (tobramycin)
Anti-fungal agents (amphotericin B)
Antiviral agents (ganciclovir)
What is an example of surgical adjuncts?
Irrigating solutions
What is an example of diagnostic drugs?
Sodium fluorescein
What is an example of topical anesthetics?
Tetracaine
What is an example of protectants & artificial tears?
Methylcellulose
What are three common opthalmic dosage forms?
Solutions (eyedrops)
Suspensions
Ointments
What are four new ophthalmic dosage forms?
Controlled Release devices
Ocular inserts
Gels, gel-forming solutions
Intravitreal injections and implants
What is the cornea?
Front clear, transparent tissue and is supplied with oxygen and other nutrients by lacrimal fluid
-Powerful refracting surface, allows light to enter the eye and provides much of the focusing power
What is the iris?
Part of the eye that gives it color
- Consists of muscular tissue that responds to surrounding light, making the pupil, or curricular opening in the center of the iris larger or smaller depending on brightness
What is the lens?
Transparent, biconvex structure, encased in a thin transparent covering
- Functions to refract and focus incoming light onto the retina
What is the retina?
Innermost layer in the eye
Coverts images into electrical impulses that are sent along the optic nerve to the brain where the images are interpreted
What effects drug availability?
Rapid solution drainage by gravity, induced lacrimation, blinking reflex and normal tear turnover
Low corneal permeability (acts as a lipid barrier
What is a typical drop volume, precorneal space of a healthy person and optimal volume administered? (in microliters)
20-50
7
5-10
How much applied drug is typically absorbed?
1-5%
Usually less than 3%
What is the retention time of ophthalmic solution on the eye surface?
Very short, 1-2 minutes
Fluids are rapidly removed from the eye by what?
Lacrimal drainage
Poor bioavailability leads to what/
Protective mechanisms (blinking, reflex lacrimation, nasolacrimal drainage) or anatomy of the eye (barrier properties of the cornea)
What is common to all ophthalmic dosages forms?
- Requires sterility of the finished product
- Appreciation for the sensitivity of ocular tissue to irritation and toxicity
- Inherent limitations in topical ocular absorption of most drugs
Define ophthalmic solutions
Sterile solutions, essentially free from foreign particles, suitably compounded and packaged for instillation into the eye
- Sterile
- Buffered
- Isotonic
- Non-irritating
- Non-greasy
- Efficacious
What are the most common means of administering a drug to the eye?
Solution
Xalatan Opthalmic solution (lantanoprost) is used for?
treatment of glaucoma
What are advantages of ophthalmic solutions?
Dosage uniformity
Little physical interference with vision
What are disadvantages of opthalmic solutions?
Relatively brief contact time
Contact time may be increase to some extent by inclusions of a viscosity-increasing agent (methylcellulose)
Define Ophthalmic suspensions
Drug is dispersed in the solvent and exist in fine particulate form
Drug is finely divided in an aqueous vehicle containing suitable suspending and dispersing agent
If the drug is not sufficiently soluble
Requires vigorous shaking
How much of the particles should have a size less than 10 micrometers or less?
95%
Define ophthalmic ointment
A drug intended for ocular use is formulated in ointment base
Characteristics of ophthalmic ointment?
Semi-solid dosage form
Contain a white petrolatum-mineral oil base
Anhydrous lanolin
PEG-gelled mineral oil base
What are advantages of ophthalmic ointment?
Longer contact time and greater total drug bioavailability
What are disadvantages of ophthalmic ointment?
Slower onset and time to peak absorption
Dosage variability is greater than with solutions
Interfere with vision unless use is limited to bedtime instillation
Must be sterile and free from particulate matter
Define ocular inserts
Sterile solid or semisolid preparation s, with a thing, flexible and multilayered structure, for insertion beneath the eyelid and release drug at constant rate
Disadvantages of ocular inserts?
Non-contact lens wearers find them difficult to administer
Non-biodegradable inserts must be removed from the eye when drug is gone
Inner eyelid discomfort
Ocusert Pilo-20 and Pilo-40 Ocular system
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 for treatment of glaucoma
Define erodible ocular insert
Soluble inserts consists of water-soluble polymer or collagen that at the end of their release, the device dissolves or erodes
Define Lacrisert
Sterile ophthalmic insert use in the treatment of dry eye syndrome
- 5 mg of hydroxypropylcellulose in a rode-shaped form
- Insert is placed in the eye 1-2 times a day where it softens and slowly dissolved
What is an ocular pack?
A cotton pledget saturated with an ophthalmic solution
The pledget is inserted into the superior or inferior fornix
Give prolonged contact of the solution with the eye
What is an example of ocular packs?
Used to produce maximal mydriasis such as cotton pledgets saturated with phenylephrine solution
Define intraocular dosage forms
ophthalmic products that introduced into the interior structure of the eye primarily during ocular surgery
What are characteristics of intraocular dosage forms?
Sterile and pyrogen-free
Strict control of particulate matter
Compatible with sensitive internal tissues
Packaged as preservative-free single dosage
Provides sustained or controlled releases
What are intraocular solutions and uses?
Used in surgical procedures such as cataract removal
- Irrigating solution: helps to maintain ocular structure and tissue hydration during surgery
- Dispersive: maintain and preserve space as well as displace and stabilize tissues
What are intraocular injections?
Allows direct application of drugs to the affected area of the eye with minimal systemic side effects
How are intraocular injections performed?
Topical anesthetic is applied directly to the eye
Eye is rinsed with an iodine solution to reduce the risk of infections
Allow 5 minutes for the anesthetic and iodine solution to take full effects
Injection is given using a very fine needle just outside the pupil
What are the intravitreal injections?
Injections into the vitreous chamber (amphotericin B, gentamicin sulfate, certain steroids)
Important for patients with retinal vascular diseases (Avastin, Lucentis, Kenalog)
What are intracameral injections?
Injections into the anterior chamber (acetylcholine chloride, alpha-chymotrypsin, carbamylcholine chloride, antibiotics and steriods)
What are ophthalmic preparation characteristics?
Sterile and free from particulate materials Must have phsiological pH Isotonic Stable Free from toxicity
Define sterility
The absence of living microorganisms and undersirable particulate material Absolute term (either is or not)
How can sterility be achieved?
Filtering the final solution using a membrane filter
Packaged in a clean, particle-free, sterile container
Longer than 24 hours or multi-dose, a preservative must be added
Use aseptic techniques in clean and aseptic area
Use of a laminar-flow hoods, and proper garments
What are some sterilization mechanisms?
Dry heat FIltration Gas sterilization Ionizing radiation Moist heat under pressure
What excipients may an ophthalmic solution may contain?
Vehicles Buffers Tonicity adjustors Preservatives Antioxidants Viscosity inducing agents
What is a vehicle?
USP WFI (water for injection) for intraocular production
EX for solutions: sterile water or saline soltuion
EX for ointments: mineral oil or petrolatum
EX for moisture-sensitive and non-water soluble drugs: mineral oil and vegetable oil
pH of buffers?
Ideal ophthalmic preparations pH: equivalent to the tear fluid value of 7.4
Outer surfaces of the eye tolerate pH: 3.5-8.5
Normal useful pH range: 6.5-8.5
What is boric acid?
Vehicle
1.9% solution of boric acid in purified water
It is isotonic with tears (pH ~5)
What is Sorensen’s modified phosphate buffer?
Containing NaH2PO4 and Na2HPO4
Not isotonic, pH range: 6.5-8.0
What is a tonicity modifier?
Solution that are isotonic with tears are preferred
The eye can tolerate within the equivalent range of 0.6-2% NaCl without discomfort
0.9% NaCl is ideal
What are examples of tonicity adjustors?
Sodium chloride
Sodium nitrate
Sodium sulfate
Dextrose
What is a preservative?
Added to maintain sterility of an ophthalmic preparation during use
What can’t a preservative be used for?
Preparation used during eye surgery
Preparations used for traumatized eyes (some irritate eyes, preservative free: single use containers)
Before adding a preservative what should be checked?
Patient sensitivity, compatibility of the preservative with all other ingredients in the formulation
What are four examples of antioxidants?
Sodium bisulfite
Sodium metabisfulfite
Thiourea
Ethylendediaminetetraacetic acid
What are two examples of wetting agents?
Polysorbate 80
Polysorbate 20
What are viscosity enhancers?
Use to thickne the tear and prolong corneal contact time and thus enhance drug absorption and activity
Viscosit increased up to the 15-50 cps range significantly improves contact time in the eye
What are some examples of viscosity enhancers?
Polyvinyl alcohol 1.4% Polyvinylpyrrolidone 1.7% Methylcellulose 2.0% Hydroxypropyl methylcellulose 1.0% Hydroxyethylcellulose 0.8%
What are advantages of packaging in plastic dropper bottles?
Flexibility and inertness: low-density polyethylene resin dropper
Compatible/low contamination potential/low cost
What are disadvantages of packaging in plastic dropper bottles?
Permeable to a variety of substances
Label glues, inks, dyes, that may penetrate polyethylene, leach out of the plastic into the contained solution
What are advantages of packaging in a glass dropper bottle?
Used for products that are extremely sensitive to oxygen or contains permeable components that are not stable in plastic
Type 1 glass should be used
Amber glass for light resistance
What are packaged in metal tubes?
Ophthalmic ointments with ophthalmic tip
Sterilized conveniently by autoclaving or ethylene oxide
Tubes can be lined with epoxy or vinyl plastic if metal reactive
