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Pharmaceutics > Routes Of Administration (Aural & Nasal) > Flashcards

Routes Of Administration (Aural & Nasal) Flashcards

1
Q

What are the typical therapeutic areas for nasal drug delivery?

A
  • Local delivery: nasal allergy, congestion infection
  • systemic delivery
  • vaccine delivery
  • access to CNS
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2
Q

What are the advantages of the nasal route?

A
  • Easy to administer
  • non-invasive, painless
  • avoids first-pass effect
  • direct route to brain possible
  • could achieve better systemic bioavailability than the oral route
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3
Q

What is the nasal anatomy?

A
  • Nasal cavity is divided by 2 halves by nasal septum
  • covered with mucus membrane containing goblet cells secreting
  • absorption occurs across turbinates and septum
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4
Q

How do lipophilic drugs transport across nasal cavity?

A
  • Transported transcellularly by concentration dependent passive diffusion, by receptor carrier mediated & vesicular transport mechanisms.
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5
Q

How do polar drugs pass through epithelium?

A
  • Via gaps between cells. So limited to drug molecular size > 1000 da
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6
Q

What is the nose brain pathway?

A
  • The olfactory mucosa is in direct contact with the brain & cerebral spinal fluid
  • drug can absorb across olfactory mucosa & enter cns
  • can bypass blood brain barrier = rapid
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7
Q

What are the functions of the nasal airway?

A
  • Act as a passageway for the movement of air into the respiratory tract & an air conditioner to humidity warm the air
  • Large particles trapped undergo rapid clearance and move towards pharynx
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8
Q

What are the benefits of using the nasal route to treat locally?

A
  • Deliver directly at site of action
  • Permit rapid relief at much lower dose
  • Reduce systemic effects
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9
Q

What are the benefits of using the nasal route to treat systemically?

A
  • Intranasal delivery where emergency situations and rapid action is required
  • Nasal delivery of peptides has been successful although with low bioavailability (portion entering bloodstream)
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10
Q

What are factors affecting systemic absorption?

A
  • Solubility
  • Lipophilicity/ Hydrophilicity
  • Molecular size
  • Degree of ionisation
  • Enzymatic activity
  • Mucosal contact time
  • Nasal epithelium permeability
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11
Q

How does solubility affect systemic absorption?

A
  • Drug must be in solution to be absorbed
  • Only 25-200ul can be administered intranasally
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12
Q

How can the problem of solubility in nasal route be overcome?

A
  • As suspension or micro size powder, but requiring drug to dissolve first in nasal cavity before absorption
  • Selection of different salt of an ionisable drug
  • Excipients (co solvents)
  • Modification of molecular form (pro drug)
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13
Q

How does lipophilicity or hydrophilicity affect systemic absorption?

A
  • Lipophilic: rapidly absorbed from nasal cavity by transcellular route with bioavailability same as IV
  • Hydrophilic: absorbed via paracellular route (between cells) and the route provides smaller area for absorption
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14
Q

How does Molecular Size affect systemic absorption

A
  • The rate of absorption is inversely proportional to weight
  • Particle size of 10-50 microns are best : Too small (pass onto lungs), Too big (run-out of nose)
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15
Q

How does Degree of Ionisation affect systemic absorption?

A
  • Nasal mucosa has a pH of 7.4 whilst mucus has a pH of 5.5-6.5
  • Formulation close to nasal mucosa minimises irritation
  • Unionised drug with higher LogP (conc of drug in oil: conc of drug in aq) is better absorbed than ionised form
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16
Q

How does Enzymatic Activity affect systemic absorption?

A
  • Broad range of enzymes are in the nasal cavity (mono oxygenases, cytochrome P450, proteolytic enzymes)
  • Drugs may be metabolised in the lumen or pass across epithelium
  • Some possible solutions: use enzyme inhibitors, use prodrugs, encapsulate drug
17
Q

How does Mucosal contact time affect systemic absorption?

A
  • Increase residence time of drug in turbinates (shell shaped networks of bone, vessels and tissue)
  • Mucoadhesive polymers can prolong drug in contact with mucosa
  • Increase formulation viscosity (increases residence time)
  • However increasing contact time not necessarily increase absorption (rate of diffusion decreased due to high viscosity)
18
Q

How does Nasal epithelium permeability affect systemic absorption?

A
  • The mucus layer is a diffusion barrier
  • Permeability of small, uncharged molecules are less affected compared to larger, cationic molecules
  • Penetration enhancers can alter epithelium structure and increase permeability
19
Q

What are the main components of nasal liquid formulation?

A
  • API
  • Antimicrobial preservatives
  • Antioxidants
  • Solubilising agents or co-solvents
  • Salts (for adjusting pH and tonicity)
  • Humectants (reduce irritation to nose)
  • Viscosity-enhancing agents
  • Absorption enhancers
20
Q

What are the main nasal devices?

A
  • Dropper/ squeezer: Cheap and flexible. Can apply liquid uniformly. Liquid delivered too quick (causes cough). Based on patient technique
  • Nasal Spray: Both solution and suspension. Easier and faster to administer but requires priming (preparing before use)
  • Nasal Tubes: Local effects for creams and gels. Messy to apply
21
Q

What are the different drug treatments for the ear?

A
  • Antibiotics
  • Anti inflammatories
  • Antiseptics
  • Cleaning solutions
  • Wax softeners
22
Q

What are the different dosage forms available to be used for the ear?

A
  • Drops: topical use, either solution or suspension, with suitable vehicle (water, glycerol)
  • Sprays
  • Washes
23
Q

What is ear wax?

A
  • Normal bodily secretion which provides a protective film on meatal skin
  • Only removed if causes deafness or interferes with ear drum
  • Composition of ear wax: mostly lipophilic (keratin, lipids, fatty acids, cholesterol)
24
Q

What are Cerumenolytics?

A
  • Acts by softening the cerumen and lubricating the canal, facilitating ear wax removal
  • E.g: Olive or almond ear drops, sodium bicarbonate ear drops
25
Q

What is the Otitis externa?

A
  • Inflammatory reaction of the meatal skin
  • Mostly caused by bacteria or fungus
  • Many recover after cleansing of the external ear canal or dry mopping. Corticosteroid ear drops can be used
26
Q

What are Astringent preparations?

A
  • An astringent is a substance that causes shrinking or constriction of body tissues, usually locally after topical medicinal application.
  • Aluminium acetate ear drops (13%)
27
Q

What are corticosteroid preparations?

A
  • Are often formulated in combination with anti-infective drugs
  • Reduce inflammation and irritation to skin
28
Q

What are Acetic Acid preparations?

A
  • Acetic acid (2%) is used to treat mild otitis externa
  • Possess antibacterial and antifungal activities

Pharmaceutics (12 decks)

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