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60 Cards in this Set
- Front
- Back
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WEEK 1
DPA's: - Definition - Purpose |
- Diagnostic Pharmacological Agents
- To assist diagnosis or refraction in eye testing procedures |
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WEEK 1
TPA's -Definition -Purpose |
-Therapeutic Pharmacological Agents
-To treat eye conditions |
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WEEK 1
Arguments for TPA's (4) |
- Increase Eye care services to Australian community (ageing problem)
-Appropriate use of optometry skills -integral part of primary eye care -better use of government money |
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WEEK 1
Arguments against TPA's (according to optometrists) (4) |
-Extra training, extra work, no profit
-Increased insurance costs -Effect on traditional services -Opposition from 3rd parties |
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WEEK 1
Instillation Technique for Solutions/Suspensions |
- Wash Hands
-Tilt head back, gaze upward -Form cul de sac (temporal aspect) -1 drop only -Close eye gently and/or punctal occlusion |
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WEEK 1
Instillation Technique Ointments |
-Pouch with lower lid
-Apply ~1cm strip -Close eye for 1-2mins -Remove excess with tissue |
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WEEK 1
Case History; Allergies |
Consider similar drug allergies to ocular drugs eg. anaesthetics
Several Drug allergies - allergic predisposition Preservatives eg. BAK |
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WEEK 1
Informed Consent |
Explain why procedure is necessary and disclose risks
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WEEK 1
Precautionary examinations before DPA instillation |
AC angle, corneal assessment, tonometry, Ophthalmoscopy, BP (sympathomimetics)
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WEEK 1
Record Card Notes |
Drugs used, tonometer used, time of day, C/D ratio, colour of ONH, findings and management, Post-instillation advise, refusal of drops, purpose of DPA
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WEEK 2
Cornea vs Conjunctiva |
Cornea is route of absorption for 4/5 of drug
Conjunctiva is an alternative route for 1/5 of drug |
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WEEK 2
Corneal Epithelium as a barrier |
2/3 is bilipid cell membrane; barrier to hydrophilic drugs, depot for lipophilic drugs, alter permeability easily
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WEEK 2
Corneal Stroma as a barrier |
1/3 of cells, easy passage for hydrophilic drugs, binds negatively charged elements
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WEEK 2
Corneal Endothelium as a barrier |
1 cell layer thick, leaky, not major barrier or reservoir
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WEEK 2
Partition coefficient |
Distribution of compound between alcohol (lipid) and water
Plot partition coefficient vs corneal permeability, parabolic curve Coefficient too low; drugs don't penetrate epithelial barrier (too hydrophobic) Coefficient too high; drugs remain in epithelium, slow diffusion into AC |
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WEEK 2
Ionisation and Corneal Penetration |
Ionised form; water soluble A- BH+
Non-ionised form; lipid soluble HA B Rel concentration depends on concentration of H+ (pH and pKa of drug) A good drug is easily able to change between ionised and non-ionised forms |
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WEEK 2
pKa |
pH at which
free base = ionised salt (can easily accept/reject H+) OR concentration ionised = concentration non-ionised |
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WEEK 2
Tear mixing |
Unknown dilution of drug within tears
Drug concentration in tears is 50% at maximum Drug absorption depends on corneal contact time |
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WEEK 2
Fick's Law |
Rate of drug diffusion across barrier is linearly dependent on concentration difference across the barrier
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WEEK 2
First order kinetic principles |
Aqueous level is maximum at 3 hours
Lag time; time difference between drug instillation and appearance in aqueous, reflects rate of diffusion across cornea |
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WEEK 2
Tears |
pH ~7.4
Drug pH can be monitored to improve absorption |
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WEEK 2
Epithelial Disruption |
Improves drug delivery, eg. BAK (common allergy)
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WEEK 2
Inactive ingredients Aims (4) |
-Aid retention time
-stabilise tears -maintain sterility -improve comfort |
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WEEK 2
Inactive ingredients List ingredients (6) |
Viscosity enhancers - incr retention time
Preservatives - sterility Tonicity Agents - prevent irritation and ocular damage Buffers - maintain pH, less irritation Antioxidants - delay deterioration by oxygen Wetting Agents - decr surface tension, spread drug across ocular surface |
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WEEK 2
Drug Vehicle Alters... |
Kinetics and corneal penetration; increased contact time increases absorption
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WEEK 2
Viscosity of Gels, Effectiveness |
Shearing of gel by blinking provides fresh surface for the release of drug, hydrophilicity of gelling polymer, diffusion constant
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WEEK 2
Other ocular barriers |
Blood-retinal, blood-vitreal, blood-aqueous; barrier to large molecules, allow passage to small and lipophilic molecules
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WEEK 2
Effect of Inflammation |
Increases permeability of blood vessels (especially iris), clinically presents as aqueous flare, allows greater penetration of drug
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WEEK 2
Solutions |
Water-based
Drug immediately available for absorption, drain rapidly |
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WEEK 2
Suspensions |
Dispersion of drug with low water-solubility, shake vigorously
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WEEK 2
Emulsions |
Oil-water mixtures, behave like solutions and suspensions
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WEEK 2
Ointments |
Lanolin in mineral oil and petroleum base, semisolid, increased retention time, fornices - drug reservoirs, can have local allergic reaction
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WEEK 2
Gels |
Polymer-based aqueous gels, alternative to ointments, incr contact time
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WEEK 2
Sprays |
Atomiser, uncooperative patients, kids
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WEEK 2
Paper Strips |
Dyes
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WEEK 2
Ocuserts and Ophthalmic Rods |
Not common, pilocarpine and lacuserts
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WEEK 2
Contact Lenses and Collagen Shields |
CL of hydrophilic polymers, pre-soaked with drug, prolong delivery, degree of lens hydration affects release rate, ALSO; protect cornea, promote corneal epithelial healing
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WEEK 2
% of applied drug that is absorbed... Due to... |
Only 1-10% is absorbed
Tear turnover, protein binding, enzyme metabolism, stinging (reflex tearing) |
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WEEK 2
Decreased tear volume... |
Increases drug concentration, common in elderly and dry eye sufferers
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WEEK 2
Multiple Drops |
increases washout, increases systemic dose, decreases ocular drug effect/unit
After 30 sec; 45% washout, 2 min; 17% washout, 5 min; no washout Aid with punctual occlusion/eyelid closure |
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WEEK 2
Ointments; Uses (4) |
Lid disease, night time therapy, antibiotics under patch/bandage, children
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WEEK 2
Ointments; Disadvantages (6) |
Difficult to self administer
Impaired healing/entrapment May impede other drug delivery Imprecise dosing Visual disturbance/blurring contact dermatitis |
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WEEK 2
Solid Delivery Devices |
Zero Order Kinetics; Rate of Delivery equals rate of elimination, stable drug levels
Convenient; less frequent doses Not commonly used; expensive, difficult to insert in elderly lx's, freq irritation eg. Lacrisert or ocusert |
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WEEK 2
Oral Administration |
Systemic effects, high levels to inaccessible sites, overcome corneal penetration problem, very little gets delivered; blood ocular barriers
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WEEK 2
Ocular Injections |
Subconjunctival, sub-tenons, retrobulbar
Anaesthetics for surgery Intracameral; AC Intravitreal |
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WEEK 2
Systemic injections |
Subcutaneous, intramuscular, intravenous
Bypass GI system |
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WEEK 2
Experimental forms of drug delivery Colloidal Forms |
Liposomes, nanoparticles, micro emulsions, nano-emulsions, sustained release, overcome barriers
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WEEK 2
Experimental forms of drug delivery Microneedle |
Coated with drug, inserted in eye, molecules dissolve, needle removed
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WEEK 2
Experimental Forms of Drug Delivery Ultrasound and Iontophoresis |
Electrical current alters scleral/corneal permeability, drug inserted trans-sclerally
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WEEK 2
Experimental Forms of Drug Delivery Intraocular Implants |
Controlled long lasting drug delivery for sight threatening pathologies
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WEEK 2
Drug Distribution Pigment Binding |
Low affinity binding for lipid soluble drugs; usually reversible, darker irises have slower drug onset and longer duration, opposite for lighter irises, potential for local toxicity - CB, iris, RPE
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WEEK 2
Drug Distribution Crystalline Lens |
Capsule prevents entry of large proteins, hydrophilic drugs of high MW are not absorbed, lipid soluble drugs can slowly pass into lens, cataract enhancement, IOL's alter movement of drugs into posterior chamber (more rapid)
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WEEK 2
Drug Distribution Vitreous Chamber |
Unstirred fluid; free diffusion for small molecules from AC, reservoir for drugs and metabolites
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WEEK 2
Drug Distribution Retina |
RPE tight junctions prevent drugs entering blood, lipophilic drugs can cross
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WEEK 2
Drug Metabolism |
Can activate or terminate a drug; prodrug vs soft drug
CB and Cornea are significant metabolising site. usually makes drug more hydrophilic - ease of excretion |
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WEEK 2
Prodrugs |
Drug metabolite is active form, converted by predictable tissue enzymes
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WEEK 2
Elimination |
Drug eliminated from AC along with outflow of aqueous, rapid turnover
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DPA use in Qld
Health Regs 1996 |
Appropriately qualified optom can obtain, administer and possess at practice:
- <1.0 cyclopentolate - <0.4 oxybuprocaine -<2.0 pilocarpine - <0.5 proxymetacaine - <1.0 tropicamide Authorised to administer <2.5 phenylephrine Drugs must be stored where public cannot access |
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DPA use
Health Practitioner Regulation National Law 2009 |
anaesthetics - 0.5 or less
tropicamide 1.0 or less cyclopentolate 1.0 or less atropine 1.0 or less homatropine 2.0 or less pilocarpine 2.0 or less physostigmine 0.5 or less phenylephrine (S2) 5.0 or less |
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History of Optom TPA use Qld
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2005 legislation - 28 drugs, 300 registered optoms, shared-care glaucoma, no high potency steroids, UG therapeutics program
2009 nation registration - can supply Board approved S2, 3, 4, medicines for eye condition Tx |
