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PMY2006 Pharmaceutical Technology > Ocular Systems > Flashcards

Ocular Systems Flashcards

1
Q

Name the 9 eye diseases?

A 
Allergies
Blepharitis 
Age-related macular degeneration (AMD)
Uveitis 
Conjunctivitis (pink eye)
Dry eyes
Cataract
Diabetic eye disease
Glaucoma
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2
Q

Describe uveitis.

A

Inflammation of middle layer of the eye causing pain and changes to vision. May cause glaucoma and cataracts.

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3
Q

Infoooo

A

Cornea is made of 3 distinct layers so the drug must possess certain physicochemical properties so that the drug can permeate across membranes into the aqueous humour.

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4
Q

What two layers must the periocular injection pass to reach retina layer?

A

Sclera - white portion of eye

Choroid - where blood flow occurs - supplies nutrients

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5
Q

What is intravitreal injection?

A

Injection straight into eyeball.

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6
Q

What are 5 physiological barriers of the eye?

A 
Tear production/blinking
Cornea
Sclera
Protein binding 
Drug metabolism
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7
Q

What is the action of mydriatics and cycloplegics? Name two drugs and the dosage forms available.

A

Dilation of pupils for the examination of fundus of the eye.
Tropicamide and Cyclopentolate.
Eye drops, eye ointment.

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8
Q

What is the action of beta blockers for the eye? Name two drugs and the dosage forms available.

A

Reduce aqueous humour production to lower intraocular pressure in treatment of glaucoma and for ocular hypertension.
Timolol and Betaxolol.
Eye drops, suspension, gel-forming solution.

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9
Q

How are drugs transported across the cornea for topically applied drugs?

A
  1. Passive diffusion along concentration gradient, paracellularly or transcellularly across the cornea.
  2. Carrier-mediated active transport.
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10
Q

What is the Log P value of an effective drug?

A

Log P = 2-3

Better efficacy, therapeutic effects and so less frequency of dose required.

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11
Q

What does the fraction of unionised drug vs ionised drug depend on?

A

pKa of the drug
pH of eyedrops and lachrymal fluid
(lachrymal fluid dilutes drug)

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12
Q

Corneal charge and drugs.

A

Corneal epithelium is NEGATIVELY CHARGED - hence charged cationic drugs permeate more easily through cornea than anionic drugs.

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13
Q

What should the size of the molecules be to allow easier transport across the cornea?

A

500 daltons.

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14
Q

When physicochemical properties of the drug are not considered optimum to reach the site of action in the eye, what can be done?

A

Use a prodrug.

Prodrug enzymatically/ metabolically/ chemicals is converted to the parent drug which has therapeutic effects.

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15
Q

What are the 4 routes of administration of drug into the eyes?

A
  1. Systemic (parenteral)
  2. Oral tablets etc
  3. Periocular/intravitreal injection
  4. Topical - eyedrops
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16
Q

What are the issues in using systemic route for administration into the eye?

A

Only small amount of drug reaching site due to poor bioavailability and solubility.
Poor penetration of drug.
Dilution occurs hence large doses administered - cause toxic side effects.

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17
Q

What is an issue with periocular injections?

A

Needle phobia.

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18
Q

What are the two parts of eyes called?

A

Anterior - front

Posterior - back

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19
Q

What are the three layers that the cornea is made from? State whether they are hydrophobic/philic.

A

Epithelium - hydrophobic
Endothelium - hydrophobic
Stroma - hydrophilic

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20
Q

What causes loss of product when topical drugs are applied to eyes?

A

Eye drops removal rapid due to tears and blinking. Tear production occurs due to change of pH of eye caused by drug.

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21
Q

What is the action of miotics? Name two drugs and the dosage forms available.

A

Constriction of pupil for treatment of glaucoma.
Pilocarpine and Carbochol.
Eyedrops, viscous eyedrops, ocular insert, gel.

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22
Q

What is the action of local anaesthetics for the eye? Name two drugs and the dosage forms available.

A

Irreversibly blocks pain receptors. Used in tonometry and before minor surgery.
Oxybuprocaine and Amethocaine.
Eyedrop solution.

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23
Q

Some drugs are use for diagnostic purposes. Name the drug, its action and dosage form available.

A

Fluorescein sodium colours the eye to aid in locating areas of damage.
Eye drops.

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24
Q

What is tonometry?

A

Device placed on cornea of eye to measure pressure.

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25
Q

Sometimes artificial tear preparations are used for eye lubrication. Name the drug, its clinical use and dosage forms available.

A

Hypromellose polyacrylic acid to treat tear deficiency.

Eye drops, viscous eye drops, gel.

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26
Q

What are 4 physicochemical properties that affect the rate and route of permeation into the cornea?

A

Solubility - hydrophilicity/lipophilicity.
Molecular size and shape.
Charge.
Degree of Ionisation.

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27
Q

Describe paracellular and transcellular passive diffusion.

A

Paracellular diffusion is between cells (through intercellular spaces) - for hydrophilic drugs.
Transcellular diffusion is through the cells - for hydrophobic drugs.
Drugs with both properties - permeate efficiently.

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28
Q

Define bioavailability.

A

Bioavailability is the rate and fraction of drug administered which successfully reaches site of action.

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29
Q

What is a prodrug as eye medication?

A

Drug administered into the eye - crosses the barrier and converts to its active form via enzymatic breakdown of the molecule.

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30
Q

What is the benefit of using prodrug for eye?

A

Increases BIOAVAILABILITY, POTENCY, SOLUBILITY and STABILITY with decreased side effects.
(enhance drug levels in eye - better therapeutic outcome).

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31
Q

List the 5 formulations/preparations available for treatment of eyes.

A 
Solutions
Suspensions
Ointments
Water-Based Gels
Ocular Insert
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32
Q

What are the 4 advantages of using solution preparations?

A
  1. Solutions mainly have water soluble compounds.
  2. High solution concentration can be achieved due to high solubility.
  3. Easy to manufacture.
  4. Better dose uniformity and ocular bioavailability.
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33
Q

What is the disadvantage of using eye drop SOLUTIONS?

A

Rapidly drained from eye.

34
Q

What can be done to decrease drainage from eyes when using solution eydrops?

A

Incorporate viscosity-increasing agents in solutions = increase tear viscosity and lowers drainage - drug retained in eyes for longer.
(High viscosity products - not well tolerated by eye.)

35
Q

What range of viscosity must be used?

A

10cP to 25cP.

36
Q

Describe water-based gels as ophthalmic formulations.

A

These are preparations containing polymers that are liquid formulations upon administration but a gel on contact with eye allowing drug to be retained for longer.

37
Q

List the reasons why there would be a phase change from liquid to semi-solid in water-based gel preparations.

A
  1. change in pH
  2. change in temperature
  3. change in ionic strength of tear film
38
Q

What are the advantages of using gels?

A
  1. As drug will be retained for longer by gel, frequency of doses will be lower.
  2. Improved patient compliance - in situ gelling process of timolol.
  3. Ease of administration.
39
Q

Describe suspension ophthalmic preparations.

A

Aqueous or oily suspension eye-drop formulations may be considered for drugs that are poorly water soluble, or because of poor aqueous drug stability.
Drug particle size must be <10mcgm

40
Q

What are the advantages of using suspensions?

A
  1. Prolong drug retention in eye.
  2. Drug retention in tears (particles dissolves slowly)
  3. Improves ocular bioavailability.
41
Q

What are the disadvantages of ophthalmic preparations?

A

Pose a physical stability problem.

  • dose uniformity
  • increase in particle size with time
  • difficult to manufacture in sterile conditions
42
Q

Describe ophthalmic ointments preparations.

A

Semi-solid preparations intended for application in the conjunctiva.

43
Q

What are advantages of ointments?

A
  1. Increased drug contact time - allows drug to permeate across cornea.
  2. Better bioavailability.
44
Q

What is disadvantage of ointments?

A

Messy
Night-time application as it can cause blurred vision
- hence poor patient compliance

45
Q

What are the 5 packaging design criteria?

A
  1. Materials are compatible with the formulation and ensure product stability
  2. Sterility of the product can be achieved & assured for the entire shelf-life
  3. Materials meet pharmacopoeial and regulatory standard requirements
  4. Containers should be tamper-evident &
  5. Pack design offers ease of administration to the patient.
46
Q

What are the two requirements for ophthalmic drugs to be accepted?

A
  1. Must be sterile up to the point of use.

2. Must comply with pharmacopoeial tests for sterility.

47
Q

What are established excipients/agents? What is the positive effect of this?

A

Established excipients = already approved and tested excipients - makes process easier.

  • improves patients tolerability.
  • improves patient compliance.
48
Q

What factors to consider when ocular solution-based product is to be made? (5)

A 
Solubility
Osmolarity
Vehicle viscosity
Stabilizers
Antimicrobial preservatives
49
Q

Why might excipient, bio-adhesive agents be used?

A

Added if we want drug to be retained by eye for prolonged period of time to enhance permeation of drrg - can reduce frequency of dosage.

50
Q

Many drugs are weak bases or acids and can be formulated as water-soluble, pharmaceutically acceptable salts. What determines the choice of salt type to include in water soluble solution formulations?

A

Solubility

  • optimum solubility will increase the retention of of the therapeutic agent in the precorneal region - allows to reach maximum pharmacological effect.
  • concentration of drug in ocular agents should be high.
51
Q

What is the issue in using certain drug salts?

A

Results in pain and irritation.

52
Q

What range of pH values can the eye tolerate?

A

pH 3.5-9.0

53
Q

How does pH affect antimicrobial preservatives and parabens?

A

These become inactive at high/alkaline pH. More active in acidic pH.

54
Q

How are acrylic acid polymers - carbomer/brand: Carbochol sensitive to pH?

A

The pH within the formulation is pH4-5. The increase in pH when applied to eye causes formulation to turn to gel.

55
Q

What two chemical are used for acidic pH adjustements?

A

citric acid/sodium citrate

acetic acid/sodium acetate

56
Q

What two chemicals are used for alkaline buffer adjustments?

A

phosphate buffers

borate buffers

57
Q

If pH manipulation fails to increase the drug solubility sufficiently, what can be done?
Give 3 examples of these materials?

A

Add solubility-enhancing materials to the formulation

- polyethylene glycols, propylene glycols, polyvinyl alcohol, poloxamer, glycerin, cellulose derivatives, surfactants.

58
Q

If desired aqueous solubility is not achieved even after using solubility enhancing materials, what can be done?

A

Consider oily solution/emulsion.

59
Q

What range of tonicity is tolerated by the eye?

Tonicity is a measure is a measure of the effective osmotic pressure gradient

A

0.5-1.5% NaCl equivalents

Ideal = 0.9% NaCl (0.9%w/v)

60
Q

What is a poloxamer?

A

A temperature-sensitive polymer - liquid in formulation but turns viscous when applied to eye.

61
Q

Give 5 examples of ophthalmic solutions or suspensions?

A

Dextrose, NaCl, KCl, buffering salts, glycerol.

62
Q

Describe vehicle viscosity.

A

Increase in vehicle viscosity = increase in retention time of drug in eye.
Very high vehicle viscosity is not tolerated by the eye. Drug diffusion is inhibited and difficult application.
Irritation to eye.

63
Q

List 5 FDA approved viscosity enhancing agents.

A 
Methylcellulose
Hydroxypropyl cellulose 
Polyvinyl alcohol
Carbomer
Polyethylene glycol
64
Q

How to prevent oxidative degradation f drugs?

A

Add antioxidants or chelating agents.

65
Q

What is the issue with using plastic bottles to store ophthalmic solutions?

A

Gases permeate through container - susceptible to oxidative degradation.

66
Q

Name 5 commonly used antioxidants.

A 
Sodium bisulphite
Sodium sulphite
8-hydroxyquinolone
Ascorbic acid acetylcysteine
Antipyrine
67
Q

What 5 features should antimicrobial preservatives possess?

A
  1. Must be effective at the formulation pH.
  2. Must be stable to processing.
  3. Must be heat stable (for sterilisation).
  4. Must be stable over the product shelf-life
  5. Inert - no interaction with agents or packing material.
68
Q

Name 3 regulatory approved antimicrobial preservatives.

A 
Benzalkonium chloride
Chlorhexidine
Methylparaben  
Phenylmercuric borate
Thimerosal
69
Q

Production under clean conditions must be done. What 3 ways are eye products made?

A

Autoclaving
Filtration
Production under aseptic conditions

70
Q

Describe autoclaving.

A

Product is manufactured and packaged in the final container under clean conditions.
- sterilisation performed under most-heat sterilisation.

71
Q

Describe filtration.

A

Filtration through an appropriate filter followed by sterilsation filtration and packaging.

72
Q

Describe production under aseptic conditions.

A

Dispersion of the sterile therapeutic agents into a sterile vehicle and packaging, all done under aseptic conditions.

73
Q

Certain agents can be added into formulations for patients with damaged cornea due to burns/accidents. Explain this and describe the problem with this.

A

To regenerate corneal tissue, growth factors and proteins can be added to the formulation.
Problem - proteins and growth factors cannot stand thermal sterilisation as they will be denatures.
This formulations must be made under aseptic conditions.

74
Q

What test can be done to establish if there compatibility problems between drug, excipient and packaging?

A

Accelerated stress stability testing

75
Q

What are contact lenses?

A

Contact lenses are eye-shaped thin discs of polymer(s), designed to correct vision problems arising from refractive error.

76
Q

What are the 4 types of contact lenses available?

A

Hard lens
Semi-hard/ semi-flexible lens
Soft lens
Soft continuous wear lens

77
Q

Describe hard lenses (6).

A
  • Made from hydrophobic polymer such as poly(methyl methacrylate) (PMMA)
  • Absorb 1-2% water
  • Cheap
  • Long-lasting
  • Give excellent vision correction
  • Comfort and tolerance levels quite low
78
Q

Describe semi-hard/semi-flexible lenses (6).

A

• Made from hydrophobic gas-permeable polymer such as cellulose acetate
butyrate (CAB)
• Low water content
• Semi-flexible
• Long-lasting
• Give good vision correction
• Permit passage of oxygen through lens to cornea - prevents suffocation of cornea

79
Q

Describe soft lenses (6).

A
  • Made from hydrophilic polymer such as poly(hydroxyethyl methacrylate) (pHEMA)
  • Contain 50-80% water
  • Flexible
  • Used for 1 day – 1 month
  • Give good vision correction
  • Comfort and tolerance levels very high
80
Q

Describe soft continuous wear lenses (7).

A
  • Made from hybrid hydrogel-silicone material
  • Lower water content than hydrogel lens (~33%)
  • Flexible
  • Long-lasting (1 month)
  • Give good vision correction
  • Require no cleaning or periodic cleaning
  • Permit passage of oxygen through lens to cornea.
81
Q

What 5 agents are included in the formulation if a contact lens solution?

A

❖ Viscosity increasers – allows comfort, convenience
❖ Surfactants – allows wetting, cleaning (removes debris)
❖ Inorganic salts – isotonicity, pH, lens stability, buffering
❖ Preservative systems – efficacy, compatibility
❖ Potentiators – sequestering agents such as disodium edetate

PMY2006 Pharmaceutical Technology (10 decks)

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