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Biopharmaceutical Technology > Formulation of eye drops > Flashcards

Formulation of eye drops Flashcards

1
Q

For ophthalmic products;

A) What are eye drops? What is the BP definition?

B) What are eye lotions?

C) What are eye ointments?

D) What are contact lenses

A

A)

Aqueous or oily solutions or suspensions for instilling into the conjunctival sac

  • BP definition: eye drops are sterile aqueous or oily solutions, emulsions or suspensions of one or more active substances intended for instillation into the eye

B)

Aqueous solutions used undiluted for bathing the eye in first aid or the home

C)

Ointments for placing in the conjunctival sac or applying to the margins of the eyelids –> nighttime, long lasting, blurred vision

D)

Aqueous solutions for lubricating, cleaning and hydrating contact lenses

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2
Q

Eye drops are used as … provide SEVEN uses for eye drops.

A
  • anaesthetics
  • anti-inflammatory agents
  • anti-microbial
  • diagnostic agents
  • miotics
  • mydriatics
  • artificial tears
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3
Q

What are the FOUR major factors to consider when formulating eye drops? Briefly explain why.

A
  1. Sterility
  • ​Most important requirement „
  • P. aeruginosa (most dangerous organism)
  1. Foreign particles
    * Inflamed eye
  2. Pain and irritation
    * Unfavourable tonicity, pH (needs to be close to pH of lacrimal fluid), medicament, preservative
  3. Viscosity
    * Easy to filter, sterilise and compatible with other ingredients
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4
Q

What are FIVE formulation components of eye drops?

A
  1. Active Ingredient (s)
  2. Vehicle
  3. Antimicrobial preservative –> single-use/ multi-use container is a factor
  • sterility
    4. Adjuvants
  • pH, viscosity, tonicity (important to not cause irritation)
    5. Suitable container (part of formulation)
  • sterilisation, stability, storage
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5
Q

For antimicrobial preservative;

A) why are they used in eye drops?

B) for eyes with damaged epithelia (compromised defences), what happens?

C) cornea has a lack of vascularity, what happens?

D) Should eye drops for surgical use contain a preservative?

E) Are they needed in multi-dose eye drops that expires in 28 days after opening

A

A)

  • To maintain sterility during use and will not introduce contamination into the eyes being treated

B)

  • Easily colonised by microorganism

C)

  • Very susceptible and difficult to treat once infection is established

D)

  • Should NOT contain a preservative

E)

  • Yes
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6
Q

What are the antimicrobial preservatives commonly used in eye drops? Provide FOUR examples.

A
  • Benzalkonium chloride „
  • Chlorhexidine acetate or gluconate „
  • Chlorobutanol „
  • Organic mercurials
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7
Q

What tonicity do eye drops require? What is used to make it this tonicity?

A

Should be made isotonic with lachrymal fluid (~0.9% NaCl)

> active ingredient may not be isotonic –> adjust accordingly

eyes will tolerate 0.7-1.5% NaCl

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8
Q

What is the formula for tonicity adjustment?

A

Ciso = 0.52/FD1%

> where the FD1% the freezing point depression of a 1% solution

To calculate: w = (0.52 – a)/ b

w = the percentage w/v of the adjusting material

a = the freezing point depression of the unadjusted solution

b = the FD1% of the adjusting material

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9
Q

For Viscosity requirement;

A) What does increased viscosity result in?

B) What is the viscosity for most commercial products in millipascal second (mPas.s)?

C) How long does it take to drain a large proportion of a typical 50 ul drop from the conjunctival sac (capacity 25ul)?

A

A)

  • Affects residence time of the drop in the eye –> increased viscosity results in a increased residence time and better penetration

B)

  • 15-25 millipascal seconds (mPas.s)

C)

  • Within 30 seconds

> there will be no trace of the drop after 20 minutes

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10
Q

What are some of the properties for the ideal thickening agent? Provide SIX properties.

A
  1. Non-toxic
  2. Non-irritant
  3. Easy to filter
  4. Easy to sterilise
  5. Compatible with other ingredients
  6. Have required refractive index and clarity level –> don’t want thickening agent to cause blurred vision
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11
Q

What are 2 examples of viscosity adjusting agents?

A
  1. Hypyromellose (thickening agent)
  2. Polyvinyl alcohol (moisturising/thickening agent)

Polyvinylpyrrolidone, polyethylene glycol, and dextrin have also been used as viscolizing agents

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12
Q

For hypromellose (thickening agent –> viscosity adjusting agent);

A) What derivative of methylcellulose is it?

B) What solubility characteristics does it have?

C) What optical clarity is it?

D) What is the concentration in %w/v? Where do higher concentrations tend to form?

A

A)

  • Hydroxypropyl

B)

  • Good solubility characteristics
  • Soluble in cold but insoluble in hot water

C)

  • Good optical clarity

D)

  • 0.5-2.0% w/v
  • Higher concentrations tend to form crusts on the eyelids
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13
Q

For polyvinyl alcohol (moisturising/thickening agent –> viscosity adjusting agent);

A) What is the concentration in %w/v?

B) Does it have good or bad contact time on the eye surface?

C) Does it have good or bad optical qualities?

D) What is the concentration in %w/v? Where do higher concentrations tend to form?

A

A)

  • 1.4% w/v

B)

  • Good contact time on the eye surface

C)

  • Good optical qualities

D)

  • Withstanding autoclaving (high temps) –> can be filtered through a 0.22 ʅm filter.
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14
Q

Lachrymal fluid has a pH of 7.2-7.4, with considerable buffering capacity –> what are some factors that make the basis of choosing what pH to use?

A

pH offering the best:

  • Solubility
  • Product stability
  • Therapeutic activity
  • Comfort of the patient
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15
Q

What are the three classes of buffering agents? What pH are their buffering capabilities at?

A
  1. Borate buffer (boric acid/borax): pH 6.8-9.1
  2. Phosphate buffer (sodium acid phosphate/sodium phosphate): pH 4.5-8.5
  3. Citrate buffer (citric acid/sodium citrate): pH 2.5-6.5
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16
Q

For the following buffering agents, provide examples of eye drops they are used in;

A) Borate buffer (boric acid/borax): pH 6.8-9.1

B) Phosphate buffer (sodium acid phosphate/sodium phosphate): pH 4.5-8.5

C) Citrate buffer (citric acid/sodium citrate): pH 2.5-6.5

A

A)

  • Chloramphenicol eye drops BP 1993: pH 7.5
  • Hypromellose eye drops BPC 1973: pH 8.4

B)

  • Neomycin eye drops BPC 1973: pH 6.5
  • Prednisolone sodium phosphate eye drops BPC 1973: pH 6.0

C)

  • Benzylpenicillin eye drops: pH 6.0
  • Idoxuridine eye drops: pH 6.0
17
Q

For stability requirements, what TWO types of agents are used?

A
  1. Antioxidants
  2. Chelating agents
18
Q

Antioxidants are required in eye drops containing ….? Provide SIX answers.

A

Adrenaline, proxymetacaine, sulfacetamide, tetracaine, phenylephrine and physostigmine

19
Q

Why are chelating agents required? What is an example of one?

A

Heavy metals can catalyse breakdown of the active ingredient by oxidation and other mechanisms

  • Disodium edetate, up to 0.1%w/v
20
Q

What are the FOUR stages for the preparation of eye drops? Briefly describe each stage further.

A
  1. Compounding of the solution
    * Active ingredient to be added last, then vehicle qs. ad . to the final volume
  2. Clarification
  • Stringent requirements for the absence of particulate matter
  • Sintered glass filter or 0.45-1.2 um membrane filter –> membrane filter used to get rid of particles
  • Solution can be filtered directly into the final container
  1. Filling
  2. Sterilisation (terminal sterilisation –> sterilise eye drops in the final container)

*for sterilisation –> membrane filter 0.22 um

21
Q

Why is the filling step so important? Why must all parts of the container withstand the sterilisation process used?

A
  • Part of the total formulation
  • Protect eye drops from microbial contamination, moisture and air

All parts of the container must withstand the sterilisation process used for terminal sterilisation

22
Q

How are single-dose containers made?

A

Injection-molded polypropylene container which is sealed at its base and has a nozzle sealed with a screw cap

> No preservative

23
Q

How are plastic bottles made?

A

Bottles are made of polyethylene or polypropylene and are sterilised by ionizing radiation prior to filling under aseptic conditions with the previously sterilised preparation

24
Q

How are glass bottles made? What are some of the properties?

A
  • Most extemporaneously prepared eye drops are supplied in 10mL amber partially ribbed glass bottles
  • neutral glass – can be autoclaved more than once
  • soda glass – can only be autoclaved once
  • Natural rubber teat – 115°C for 30 minutes ok but not dry heat
  • Synthetic rubber teat – eg silicone rubber teat – withstand dry heat, permeable to water vapour – not good for aqueous preparation, limited shelflife of 3 month
  • Rubber teats absorb preservatives and antioxidants during autoclaving and storage.
25
Q

How is sterilisation achieved? Provide THREE different methods.

A
  1. ​Autoclaving at 115°C for 30 minutes or 121°C for 15 minutes
    * For rubber, lower temperature and longer time to not cause damage
  2. Membrane filtration sterilisation, 0.22um pore size membrane
  • Container has to be sterilised
  • Conducted under aseptic environment
  1. Dry heat sterilisation at 160°C for 2 hours for non-aqueous preparations –> e.g. liquid paraffin eye drops
26
Q

What are the labelling requirements by the TGA?

A

Therapeutic Goods Order No. 91

  • Standard for labels of prescription and related medicines

Therapeutic Goods Order No. 92

  • Standard for labels of non-prescription medicines
27
Q

Self-assessment questions

  1. What factors do you need to consider when formulating eye drops?
  2. Discuss the formulation requirements for preparing an eye drops
  3. Why is a container is important in eye drop formulations?
A

Biopharmaceutical Technology (16 decks)

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