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PHARM 125 - Pharmaceutics > Ophthalmic, Otic, Nasal and Pulmonary dosage forms > Flashcards

Ophthalmic, Otic, Nasal and Pulmonary dosage forms Flashcards

1
Q

What are the 3 major barriers to drug delivery to the eye?

A
  1. Corneal barrier (most important)
  2. Blood-aqueous barrier
  3. Blood-retinal barrier
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2
Q

What are the components of the corneal barrier?

A
  1. Epithelium (hydrophobic)
  2. Stroma (hydrophilic)
  3. Endothelium (hydrophobic)

The differences between the water/lipid affinity in these, we end up loosing 90% of the drug

pH of the solution matters a lot

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3
Q

What are the advantages of topical administration of ophthalmic products?

A
  • convenient
  • non-invasive
  • self-administered
  • few systemic effects
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4
Q

What are the disadvantages of topical administration of ophthalmic dosage forms?

A
  • low drug bioavailability due to drainage into nasolacrimal duct and absorption into conjunctiva membrane to the systemic circulation
  • not effective fro posterior segment diseases
  • not super convenient
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5
Q

What are some strategies for delivering ophthalmic products topically?

A
  • several applications
  • prodrug derivatizations
  • penetration enhancers
  • controlled delivery systems (liposomes and nanoparticles)
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6
Q

What amount of the dose is absorbed ocularly and where does the rest of it go?

A

Ocular absorption is ~5% of the dose

50-100% then gets into systemic absorption through the conjunctiva, nose, lachrymal drainage, etc.

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7
Q

What is periocular administration and what is it typically used for?

A

Injection usually underneath the conjunctiva, drugs diffuse to the sclera where there is high permeability

Used for antibiotics and antivirals

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8
Q

What is intraocular administration?

A

Injections to the aqueous humour or into the vitreous

**repeated injections can cause trauma to the eye

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9
Q

What is ocular iontophoresis and what is it used for?

A

Electric current helps to deliver ionized drugs to the intra-ocular tissues via cornea or sclera

Used for antibiotics

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10
Q

What are the 6 key components in ophthalmic dosage forms?

A
  1. API
  2. Tonicity adjusters
  3. Buffers
  4. Solubilizing agents
  5. Preservatives and antioxidants
  6. Suspending agents/viscosity modifying agents
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11
Q

What are some examples of tonicity adjusting agents?

A
  • sodium chloride
  • glycerin
  • mannitol
  • dextrose
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12
Q

What is osmolality and what is the osmolality of healthy non-dry eyes?

A

Osmolality = tonicity = concentration of ions in a solution

Healthy tonicity in the eyes is 302 mmol/kg

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13
Q

What are some commonly used buffers?

A

Borate and phosphate buffers, acetic acid/sodium acetate buffers

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14
Q

What is the pH of tears and what pH of formulations can the eye tolerate?

A

Tears pH = 6.9-7.5 with a low buffer capacity

Eye can tolerate topical formulations of pH 3.5-9 → best to maintain the same pH of tear fluid to avoid any excessive tear secretion and discomfort

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15
Q

What are some common surfactants used in ophthalmic dosage forms?

A

Non-ionic surfactants like polysorbate 20, polyoxyl 40 stearate

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16
Q

What are surfactants used for in ophthalmic dosage forms and what happens if they have higher or lower surface tension than lacrimal fluid?

A

Used to solubilize and disperse the drug

Lower surface tension → removes mucus layer and disrupt tight junction complex, increasing drug permeation but causing irritation

Higher surface tension → can have a problem with foaming during productions or when shaking

17
Q

What are some examples of preservatives and antioxidants in ophthalmic dosage forms?

A

Preservatives → benzalkonium chloride, chlorobutanol, methyl paraben and thimerosal

Chelating agents + antioxidants → disodium edetate, sodium bisulfite, sodium methabisulfite

18
Q

What is the function of suspending and viscosity inducing agents in ophthalmic dosage forms?

A

improve the cornea contact time by reducing drainage rate

**viscosity too high can cause pain, vision blurring and block the puncta

19
Q

What are the characteristics of the solution ophthalmic dosage forms?

A
  • most common and preferred
  • easy to manufacture and low cost
  • rapid onset of action
  • disadvantage: fast drainage
20
Q

What are the characteristics of suspensions for ophthalmic dosage forms?

A
  • provides slow dissolution and prolonged release
  • used for drugs with low water solubility and poor water stability
  • particle size should be less than 10um to avoid excessive lacrimation
21
Q

What are the characteristics of ointments/emulsions for ophthalmic dosage forms?

A
  • lipophilic bases (hydrocarbon, white petrolatum, mineral oil, o/w emulsions)
  • reduced dilution of drug with tears, prolonged retention time, better bioavailability
  • cause blurring and contact dermatitis
22
Q

What are the characteristics of gels for ophthalmic dosage forms?

A
  • increased contact time due to increase of viscosity
  • more comfortable than ointments
23
Q

What are the characteristics of ocular inserts for ophthalmic dosage forms?

A
  • prolonged and constant drug release rate
  • less affected by nasolacrimal drainage and tear flow
  • some that you can use for up to 7 days, some that dissolve on the eye and you just put another one in later
24
Q

What are the characteristics of muco-adhesive systems for ophthalmic dosage forms?

A
  • polymers used:
    • polyacrylic acid
    • plycarbophil
    • cellulose derivatives
    • chitosan
    • xanthan gum
    • pectin
    • alginate
25
Q

What are the quality tests done for ophthalmic dosage forms?

A
  • particulate and foreign matter
  • sterility
  • particle size and disribution
  • antimicrobial preservative
  • viscosity
  • drop size (from bottle should be 20-70 uL)
26
Q

What is the pH of the inside of the ear?

A

pH 6, slightly acidic environment for defence against microorganisms

27
Q

What are some examples of solutions prepared for administration to the ear?

A

cerumen removing solutions → main barrier for drug absorption, used to dissolve wax in the drops/solutions

Infections

Anti-inflammatory and analgesic preparation

28
Q

What are the vehicles that can be used for otic preparations?

A

Aqueous → purified water, ethanol (used for quick irrigation, will dry out the ear)

Non-aqueous but miscible with water → propylene glycol, glycerin, PEG 300

Non-aqueous → mineral oil, vegetable oil (aids in the solubilisation of ear wax)

29
Q

What are the preservatives found in otic preparations?

A
  • chlorobutanol
  • benzalkonium chloride
  • thiomersal
30
Q

What are the viscosity-modifying agents used for otic preparations?

A

Hydrophilic polymers, glycols and glycerol

*used to keep API from draining out of the ear

31
Q

What is the main barrier when delivering drugs to the nose?

A

Nasal mucosa: enzymatic drug degradation takes place here

32
Q

What characteristics should nasal preparations have?

A
  • pH 5-6.5
  • be isotonic
  • be compatible with normal ciliary motion and ionic constituents of nasal secretions
  • volume of delivered dose 25-200 uL/nostril
  • contain solvents and co-solvents to increase drug aqueous solubility
  • include non-irritant excipients
33
Q

Give examples the following excipients for nasal preparations:

  • tonicity adjusting agent
  • buffering agent
  • preservative
  • antioxidant
  • complexing agent
  • pH adjusting agent
  • viscosity enhancing agent
A
34
Q

What are the dosage forms for nasal preparations?

A

Liquids → most common, simple, low cost BUT no precise dosing, contamination and stability problems (sprays are more precise)

Powders → good for drugs not stable in aqueous solutions, provide local action and longer contact time with the mucosa, no need for preservatives BUT are easily cleared by nasopharynx, taste bad, poor patient compliance

Emulsions and ointments → hydrophobic ointments and hydrogels have problems with aspiration, precise dosing and are messy to apply

PHARM 125 - Pharmaceutics (5 decks)

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