L33 - Absorption Via Different Routes Of Drug Delivery Flashcards
1
Q
What is enteral drug delivery? (2)
A
- within or by way of the intestine
- enteric
2
Q
What is parenteral? (3)
A
- located outside the alimentary canal
- administered in a manner other than through the digestive tract
- bypass GI tract to reach systemic circulation
3
Q
Examples of enteric drug delivery: (4)
A
- oral
- buccal
- sublingual
- rectal
4
Q
Examples of parenteral drug delivery: (2)
A
- injections and infusions
- implantable devices
5
Q
What are common injection routes? (5)
A
- intramuscular
- intradermal
- subcutaneous
- intravenous
- (intramedullary)
6
Q
What are advantages of iv drug delivery? (3)
A
- rapid - almost immediate effect
- dose - precise, large vols possible
- 100% bioavailability
7
Q
What are disadvantages of iv drug delivery? (5)
A
- Potential toxicity – rapid Cp elevation (can be controlled by infusion)
- Suitable vein
- Professional required – admin. and monitoring
- Cost
- Duration (infusion can extend dosing)
8
Q
What are characteristics of im drug delivery? (4)
A
- rich capillary bed
- passive diffusion of drug
- blood flow important
- carrier solvent absorption
9
Q
What are advantages of im drug delivery? (2)
A
- relatively large vol
- sustained release
10
Q
What are disadvantages of im drug delivery? (2)
A
- professional required
- erratic absorption
11
Q
What are characteristics of sc drug delivery?
A
Passive diffusion into capillaries or lymphatics
12
Q
What are advantages of sc drug delivery? (3)
A
- slow, sustained delivery
- self-administration possible
- implants for long term delivery
13
Q
What are disadvantages of sc drug delivery? (2)
A
- small doses
- pain, irritation from repeated injections
14
Q
What are simple epitheliums like in terms of layers?
A
1 layer
15
Q
What are stratified epitheliums like in terms of layers?
A
> 1 layer
16
Q
What are functions of epithelia? (3)
A
- protection
- absorption
- gas exchange
17
Q
What are specialisations of epithelia? (4)
A
- keratinised layer
- vili
- cilia
- most secret mucus
18
Q
What are the different types of epithelia? (4)
A
- squamous epitheilum (alveoli)
- stratified squamous epithelium (skin, mouth)
- columnar epithelium (nasal cavity, GI tract)
- cuboidal epithelium (ductal lining)
19
Q
What is nasal drug delivery?
A
Topical delivery
- treatment of allergy, congestion and infection
20
Q
Why is nasal drug delivery used? (4)
A
- avoids first pass metabolism
- drugs sensitive to intestinal metabolism
- acid sensitive drugs
- polar compounds with poor oral absorption
21
Q
What can diffuse through nasal epithelium with bioavailability up to 100%?
A
Small, lipophilic drugs
22
Q
What does passive transcellular diffusion depend on? (3)
A
- lipophilicity
- ionisatoin
- size according to ficks first law
23
Q
What has a major impact on drug absorption in nasal drug delivery?
A
Nasal physiology
24
Q
What is the structure of the nasal cavity? (4)
A
- Volume ~20 ml
- Surface area ~150 cm2
- High density of sub-mucosal blood
supply (40 mL/min/100 g) - High air turbulence
25
What are the functions of the nasal cavity? (5)
- air conditioning:
* Temp (-20 to 55 °C ->within 10 °C of body temp.)
* Humidity(-> 97-98 %)
* Filtration
* smell
26
What are characteristics of the nasal epithelium? (3)
- pseudo stratified columnar epithelium
- large SA
- protective mucus layer and cilia for clearance
27
What is the initial hurdle in nasal drug delivery?
Deposition in the nasal cavity
28
What is the nose-to-brain drug delivery? (4)
- olfactory epithelium, no blood brain barrier present
- can enter via paracellular dif, axonal transport through
- future route to CNS
- delivery systems need to be optimised to avoid clearance
29
What is ocular drug delivery used for? (2)
Solely for treatment of local conditions
- periocular diseases
- intraocular diseases
30
What are periocular diseases eg? (5)
* Blepharitis (S. aureus infection of the eye lids)
* Conjunctivitis (infection or allergy)
* Keratitis (corneal clouding)
* Trachoma (Chlamydia trachomatis)
* Dry eye
31
What are intraocular diseases eg? (4)
* Glaucoma
* Age-related macular degeneration
* Diabetic retinopathy
- infections
32
What is the corneal structure like? (2)
- 50-100mcm thick, hydrophobic (epithilium)
- 60-1100mcm, hydrophobic connective tissue (stroma)
33
What are the 2 absorption routes for periocular?
- corneal route
- conjunctival route
34
What is the corneal route? (2)
Major route for ocular drug absorption
- transcellular (lipophilic)
- paracellular (hydrophilic)
35
What are conjunctival route in periocular?
Drug passes through conjunctiva and sclera
- most lost in local capillary bed, enters systemic circulation
36
What are alternative ocular drug delivery routes? (4)
- subretinal
- suprachoroidal (microcannula)
- intravitreal
- suprachoroidal (microneedle
37
What local treatments are vaginal drug delivery routes? (6)
* Antibacterials
* Antifungals
* Antivirals
* Antiprotozoals
* Oestrogens
* Spermicidal agents
38
Where is the interest in delivery for systemic effect via mucosal absorption in vaginal drug delivery? (4)
- oestrogens
- prostaglandins
- progesterone
- peptides and proteins
39
What is the normal pH?
4.0 to 5.0
Postmenopausal - 7.0 to 7.4
40
What is drug absorption dependent on in vaginal drug delivery
Epithelial thickness
- cycle and age dependent
41
What is pulmonary drug delivery used for?
respiratory conditions
- reduces dose needed if given via other routes
42
How are drugs delivered via lungs? (3)
- nebulisers
- dry powder inhalers
- metered dose inhalers
43
What is there a huge potntial for in pulomary drug delivery and why?
systemic delivery
- lungs oxygenate blood
44
What is the anatomy of the lungs? (7)
- larynx
- trachea
- bronchus (primary, secondary, tertiary)
- smaller bronchi
- terminal bronchi
- respiratore bronchiole
- alveoly (alveolar duct)
45
What is the particle deposition in the lungs caused by? (3)
- large particle burden
- area is related to particle size
- drugs must avoid natural defences
46
What are the 3 mechanisms in deposition in the lungs?
- inertial impaction
- sedimentation
- brownian diffusion
47
What is the transcellular pathway in pulmonary drug delivery?
Passive diffusion of small , lipophilic drugs through epithelium down a conc grad
48
What is the paracellular pathway in pulmonary drug delivery?
Passive diffusion of small, hydrophilic drugs down a conc grad between cells of the epithelium
49
What are factors affecting pulmonary drug absorption? (7) (2)
Mucus
- viscous layer
- drug solubility (absorption)
- drug size (diffusion)
- interactions
- varying thickness
- mucociliary escalator
- coughing
- large SA (rapid administration possible)
- blood supply avoids hepatic first pass
50
What are transdermal drug examples? (2)
Creams
- local conditions
- systemic effects
51
Why is transdermal drug administration used? (4)
- accesible, plenty of it
- avoids first pass
- patches deliver in a controlled manner
- good compliance, easily removed
52
What is the anatomy of the skin? (5)
- ~2 m2
* 1/3 of body’s blood supply
* Prevents water & nutrient loss
* ~1.1 mm thick
* 15-20 % of body mass
53
What is the stratum corneum like? (5)
* “Bricks and mortar” structure, ~10-30 µm thick
* Dead, flattened cells
* Inside of membrane is protein-coated
* Lipid rafts between cells (liquid crystal: Ceramides, cholesterol, fatty acids)
* Major barrier to water loss
54
What are pathways of percutaneous drug penetration? (2)
- paracellular
- shunt pathways (follicular, eccrine)
55
What are factors affecting transdermal drug absorption? (6)
- hydration of sc (patches are occlusive, water build up, it increases permeability)
- pH - 4.0 to 5.5
- age (premature babies, elders)
- injury, disease - reduce barrier action
- site - thickness varies in dif areas
- cutaneous first pass (ox, red, hydrolysis, conjugation)
56
Why is transdermal delivery used (systemic effects)? (6)
- for potent drugs
- sustained concs
- control of delivery
- reducing dosing freq
- less side effects
- can be stopped at any time
57
How can you increase skin permeability? (2)
- lontophoresis
- microneedles
58
How do you increase skin permeability - lontophoresis? (4)
- anesthetised area - 5cm2
- onset - 10 mins
- depth of analgesia - 6.4mm PD after 10 mins treatment
- duration - approx. 60 mins
59
Why increase skin permeability by microneedles? (3)
- pain free (includes biological, vaccines)
- wide range of types and materials
- temporarily increase skin permeability
