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General Ocular Pharmacology > Drug Formulation and Delivery > Flashcards

Drug Formulation and Delivery Flashcards

1
Q

List ideal characteristics of a diagnostic drug

A

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

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2
Q

What are the sources of ophthalmic drugs

A

Inorganic
Organic
Synthesised

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3
Q

List the different forms of ophthalmic drugs

A 
Aqueous solutions 
oily solutions 
ointments 
creams
colloidal solutions emulsions , suspensions , gels
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4
Q

Passage of drug inot the internal structure of the eye is mostly done through which structure of the eyes

A

cornea

less than 20% via conj and sclera

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5
Q

The cornea is often described as a fat water fat sandwich what is meant by this ?

A

epithelium - lipophillic
stroma - hydrophillic
endo - lipophillic

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6
Q

what percentage of an aqueous drop will reach the anterior chamber?

A

1%

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7
Q

Topical Anaesthetics are used prior to which types of procedures

A

invasive = tonometry and foreign body removal

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8
Q

Pre tx with TA

A

increases permeability of the cornea to drugs subsequently instilled
improve efficacy and faster effect of drug achieved

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9
Q

Give an example of a TA drug that useful to as pre tx

A

Oxybuprocaine

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10
Q

The max volume the conj sac can contain is

A

30 microlitres

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11
Q

Within the conj sac , the tear volume is approx ..

A

8-10 microlitres

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12
Q

State the volume of drug dispensed by a dropper bottle

A

Approx 27 ML

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13
Q

Instilling too much drug in the eye can cause

A
  • drainage via nasolacrimal system

- overflow down face and cheek

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14
Q

If several drops are required to be instilled , what should you do ?

A

ensure you leave enough time inbetween

2-5mins

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15
Q

How often is the total tear volume replaced

A

5-6 mins

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16
Q

How can you reduce risk of drug absorption via nasolacrimal system
and what is the disadvantage of your method

A

occlude the nasolacrimal duct

increases rate of systemic absorption via conj , limbal and episceral vessels

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17
Q

State components involved in ophthalmic preparations

A 
active ingredients 
vehicle its in 
preservatives
buffers
tonicity agents 
viscousity enhancing agents
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18
Q

List different drug delivery systems

A

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

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19
Q

Sate a disadvantage of using preservatives in drug

A

some pts may develop sensitivity and have reactions to it

20
Q

Multidose preservative free drugs have two systems - explain what each of them are

A
  1. ABAKS system
  2. 2 FILTER IN applicator that prevents ingress of infective organisms
  3. Monodose system
    - has a mechanical system used to expel only one drop of the drug n prevents ingress of infective organisms
21
Q

Using a prodrug can be useful when

A
  • active form would penetrate poorly through ocular structures
  • active form produces affects around the eyes ( allergy)
22
Q

State three properties of ophthalmic preparations

A

pH
Tonicity
Viscosity

23
Q

Discuss what you know abou the pH of ophthalmic drugs

A

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

24
Q

Give examples of Buffers

A

acetic acid
boric acid
potassium bicarbonate
sodium citrate n phosphate

25
Q

Discuss what you know about the tonocity of ophthalmic drugs

A

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

26
Q

Discuss what you know about the viscosity of ophthalmic drugs

A

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

27
Q

increase in corneal absorption by factor of two is achieved

A

by 100 fold increase in viscosity

28
Q

what would be the ideal viscosity of the following

diagnostic
therapeutic day
therapeutic night

A
  1. low V , short duration contact with eye , minima absorption of drug
  2. low V , good vision
  3. high V , smeary vision , high contact time with eye
29
Q

What would you find on the packaging of a drug

A 
name 
conc 
BN
ED
DOM
storage Req
Manafactures details 
Legal Class
Seal
30
Q

List sterilisation methods of ophthalmic drugs

A 
Heat 
Autoclaving 
Filtration
Ultrasound 
Ionising radiation 
UV light
31
Q

Heat sterilisation is useful for which type of drugs

A

thermostable drugs - don’t get destroyed by high temp

32
Q

What temp is needed kill viruses using heat

A

60o

33
Q

Autoclaving is

A

heating drug in steam environment

121 degrees for 15 mins

34
Q

Filtration of a drug is done using

A

a 0.22 mm filter
retains bacteria
not viruses

35
Q

Ultrasound is effective against

A

bacteria

36
Q

Ionising radiation is useful for

A

drug filter papers

37
Q

UV light useful for

A

killing bacteria

38
Q

Purpose of preservative is to

A

defend from microbial contamination once package is opened

39
Q

State name of commonly used preservative and its function

A

Benzalkonium chloride (BAK)
A quaternary ammonium compound
Disrupts bacterial cell membranes

40
Q

what enhances the effect of BAK

A

chelating agent called EDTA

41
Q

Discuss what you know about the minims Ophthamic preparations

A

Single use - contain half ml of drugs = 12 drops
preservative free
supplied in box of 20
sterlised via autoclaving at 115 for 30 mins

42
Q

explain the process of instilliation of minims

A

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

43
Q

When using a drug on a pt what is important to consider

A 
Four D
drug 
date 
dose 
dispose
44
Q

Ideal storage for minims

A

cool dry place less than 25 degrees

some may need fridge 2-8deg

45
Q

give examples of drugs that need to be stored in the fridge

A

minims proxymetacaine

minims chloramphenicol

General Ocular Pharmacology (6 decks)

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