Drug Formulation and Delivery Flashcards
List ideal characteristics of a diagnostic drug
Easy to administer
Rapid onset of effect
Sufficient duration of effect until procedure takes place
rapid recovery
cheap , plentiful supply , long shelf life . easy to store
no adverse reactions
no interactions
What are the sources of ophthalmic drugs
Inorganic
Organic
Synthesised
List the different forms of ophthalmic drugs
Aqueous solutions oily solutions ointments creams colloidal solutions emulsions , suspensions , gels
Passage of drug inot the internal structure of the eye is mostly done through which structure of the eyes
cornea
less than 20% via conj and sclera
The cornea is often described as a fat water fat sandwich what is meant by this ?
epithelium - lipophillic
stroma - hydrophillic
endo - lipophillic
what percentage of an aqueous drop will reach the anterior chamber?
1%
Topical Anaesthetics are used prior to which types of procedures
invasive = tonometry and foreign body removal
Pre tx with TA
increases permeability of the cornea to drugs subsequently instilled
improve efficacy and faster effect of drug achieved
Give an example of a TA drug that useful to as pre tx
Oxybuprocaine
The max volume the conj sac can contain is
30 microlitres
Within the conj sac , the tear volume is approx ..
8-10 microlitres
State the volume of drug dispensed by a dropper bottle
Approx 27 ML
Instilling too much drug in the eye can cause
- drainage via nasolacrimal system
- overflow down face and cheek
If several drops are required to be instilled , what should you do ?
ensure you leave enough time inbetween
2-5mins
How often is the total tear volume replaced
5-6 mins
How can you reduce risk of drug absorption via nasolacrimal system
and what is the disadvantage of your method
occlude the nasolacrimal duct
increases rate of systemic absorption via conj , limbal and episceral vessels
State components involved in ophthalmic preparations
active ingredients vehicle its in preservatives buffers tonicity agents viscousity enhancing agents
List different drug delivery systems
multidose dropper bottles/single dose applicators for AS
tubes for gels/ointments
solid delivery systems = collagent shields,SCL,nafl
continuous flow devices
periocular inj
direct ocular inj
- intravitreal and intracameral
Sate a disadvantage of using preservatives in drug
some pts may develop sensitivity and have reactions to it
Multidose preservative free drugs have two systems - explain what each of them are
- ABAKS system
- 2 FILTER IN applicator that prevents ingress of infective organisms
- Monodose system
- has a mechanical system used to expel only one drop of the drug n prevents ingress of infective organisms
Using a prodrug can be useful when
- active form would penetrate poorly through ocular structures
- active form produces affects around the eyes ( allergy)
State three properties of ophthalmic preparations
pH
Tonicity
Viscosity
Discuss what you know abou the pH of ophthalmic drugs
Drugs need to be close in Ph of the tear film which is approx 7.35
drugs with higher or lower ph will cause stinging
Buffers are used ot control pH
Give examples of Buffers
acetic acid
boric acid
potassium bicarbonate
sodium citrate n phosphate
Discuss what you know about the tonocity of ophthalmic drugs
cornea - semi permeable membrane
draw fluid out and inot cornea depending on tonicity
hypertonic = higher ion conc , outflow of fluid
hypotonic - lower ion conc - oedema
Discuss what you know about the viscosity of ophthalmic drugs
high V of drugs - increased contact with eye , increases chances of absorption but interferes with vision
V is controlled by vehicle its in examples
methylcellulose ,carbomers
increase in corneal absorption by factor of two is achieved
by 100 fold increase in viscosity
what would be the ideal viscosity of the following
diagnostic
therapeutic day
therapeutic night
- low V , short duration contact with eye , minima absorption of drug
- low V , good vision
- high V , smeary vision , high contact time with eye
What would you find on the packaging of a drug
name conc BN ED DOM storage Req Manafactures details Legal Class Seal
List sterilisation methods of ophthalmic drugs
Heat Autoclaving Filtration Ultrasound Ionising radiation UV light
Heat sterilisation is useful for which type of drugs
thermostable drugs - don’t get destroyed by high temp
What temp is needed kill viruses using heat
60o
Autoclaving is
heating drug in steam environment
121 degrees for 15 mins
Filtration of a drug is done using
a 0.22 mm filter
retains bacteria
not viruses
Ultrasound is effective against
bacteria
Ionising radiation is useful for
drug filter papers
UV light useful for
killing bacteria
Purpose of preservative is to
defend from microbial contamination once package is opened
State name of commonly used preservative and its function
Benzalkonium chloride (BAK)
A quaternary ammonium compound
Disrupts bacterial cell membranes
what enhances the effect of BAK
chelating agent called EDTA
Discuss what you know about the minims Ophthamic preparations
Single use - contain half ml of drugs = 12 drops
preservative free
supplied in box of 20
sterlised via autoclaving at 115 for 30 mins
explain the process of instilliation of minims
Patient tips head backward slightly
Patient directs gaze upwards (~45º)
Pull down lower eyelid
Expose inferior fornix
Apply one drop to the inferior fornix
Avoid contact with the cornea
Release eyelid. Ask patient to gently close eye
Occlude lacrimal duct when using drugs with risk of adverse systemic response
When using a drug on a pt what is important to consider
Four D drug date dose dispose
Ideal storage for minims
cool dry place less than 25 degrees
some may need fridge 2-8deg
give examples of drugs that need to be stored in the fridge
minims proxymetacaine
minims chloramphenicol
