Formulation of Advanced or Complex Medicines 21 Ophthalmic prp Flashcards
Give examples of minor eye issues
Allergic conjunctivitis
Bacterial conjunctivitis
Scleritis
Corneal infection
Why can’t eye problems be treated systemically?
Poor blood supply
Poorly permeable capillaries in retina/iris
Side effects
- high doses needed
How are eye conditions usually treated?
Topically
What are the problems with treating eye disorders?
Residence time in conjunctival sac
- increased volume = decreased time
- medication seeps out
- increased viscosity = increased time
Binding to tear problems
- affects absorption
Conjunctival drug absorption
- large surface rea
Systemic drug absorption
- nasal mucosa
What are the problems with drugs crossing the corneal barrier?
External epithelium
- lipid rich
- problem for hydrophilic drugs
Stroma
- aqueous
- problem for lipophilic drugs
Internal endothelium
- lipid rich
- problem for hydrophilic drugs
What are ophthalmic preparations?
Sterile liquid, semi-solid or solid preparations intended for administration upon the eyeball and/or to the conjunctiva or for insertion in the conjunctival sac
What types of formulations are used in ophthalmic preparations?
Liquids
- surface of the eye
Semi-solids
- margin of the eyelid/conjunctival sac
Solids
- modified release to surface of the eye
Surgical implants
- modified release within the eye
Injections
- e.g. intracorneal
Irrigations
- during surgery
What are the pharmacopoeial requirements for eye preparations?
Containers comply with requirement of Materials used for the Manufacture of Containers (3.1) and Containers (3.2)
Antimicrobial preservation demonstrated by a test described in Efficacy of Antimicrobial Preservation (5.1.3)
What are the advantages of plastic eye drop bottles?
Cheap
Lightweight
Non-fragile
Easier to use
Less contamination
What are the disadvantages of plastic eye drop bottles?
Cannot be autoclaved
- polyethylene
Sorption
- plastic can get into formulation
Permeability
How can the efficacy of antimicrobial preservation be tested?
Challenge the preparation (in final container wherever possible) with suitable micro-organisms
Store at a prescribed temperature
Withdraw samples at specified intervals of time
Count organisms in the samples
What is an eye drop?
Sterile, aqueous or oily solution, emulsion or suspension of one or more active substances intended for instillation into the eye
What are the physiochemical considerations of eye drops?
Drop size
Viscosity
Solubility
Stability
Preservation
How can bioavailability of eye drops be improved?
Increase residence time
- small drops
- < 20uL for decreased drainage
- increase concentration
- increase viscosity
What is the normal viscosity of eye drops?
Many eye drops formulated to 15 - 25 cP (centipoise) to increase residence time and bioavailability
