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MPharm > Transdermal, suppositories and aerosol > Flashcards

Transdermal, suppositories and aerosol Flashcards

1
Q

What are some advantages to transdermal patch drug delivery

A
  • Provide controlled continuous drug input over long periods
  • Readily terminated
  • Readily identifiable in emergencies
  • Readily accessible site of administration
  • Avoid variables that influence GI absorption
  • Avoid first pass metabolism
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2
Q

What are some barriers limiting percutaneous drug absorption

A

Stratum corneum - lipophilic layer, no water
Appendages
Viable epidermis
Dermis
CirculationB

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3
Q

What are some biological barriers

A

Binding to receptors
Partitioning into and retention by fat droplets
Metabolism by enzymes

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4
Q

What are ideal properties of drug transdermal delivery

A

Low mw
* <500 Da

Relatively lipophilic
* Log P 2
o Needs to go thorugh lipophilic membrane

Low mp
* <150C

Sufficient solubility in water at pH 6-7.4 to deliver required dose
* pH of the skin

Suitable pKa
* Unionised at physiological pH

High potency
* 1mg/cm/day

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5
Q

What are the design principles of transdermal patches

A

Suitable drug molecule
For immediate and sustained drug release
Apply strong driving force for drug to leave transdermal patch
* Saturate drug concentration to achieve maximum concentration gradient across skins
* Suspension of drug solids in vehicle to achieve sustained release
Apply co-solvents to modify skin permeability and drug solubility
Apply impermeable barrier to ensure occlusion - retard water loss to enhance skin hydration and permeability

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6
Q

Explain Ficks Law

A
  • Increase Cs by using appropriate excipients
  • Maintain Cs by suspending solid drug particles in system
    o Ensure constant drug release
    o Requires insoluble drug particles to ensure that concentration of Cs maintains high for diffusion
  • Diffusion force = difference in concentration from high to low
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7
Q

What is the difference between matrix and membrane system for TDDS

A
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8
Q

What are the five layers of TDDS

A

Backing layer of tan-coloured, aluminized polyester film
Drug reservoir of scopolamine, light mineral oil and polyisobutylene
Microporous polypropylene membrane to control rate of drug delivery
Adhesive layer with scopolamine priming dose
Protective peel strip to be removed before use

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9
Q

Provide some counselling points for TDDS

A
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10
Q

Quality standards and compendial requirements for TDDS

A
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11
Q

Explain the rectal formulation - local action, systemic action and diagnostic action

A

Formulation:
Enemas - solutions, suspensions and emulsions
Rectal capsules
Rectal creams, ointments and foams
Rectal suppositories

Local action:
Treatment of pain and itch due to haemorrhoids, antiseptics and laxatives

Systemic action:
Anti-asthmatics
Anti-inflammatory
Analgesics

Diagnostic action:
Barium enema

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12
Q

Explain the vaginal formulation - local action, systemic action and special consideration

A

Formulation:
Solutions
Sprays and foams
Tablets and capsules
Creams and ointments
Pessaries

Local action:
Antifungal, lubricants and antibacterial agents

Systemic action:
Hormonal imbalance - progesterone and oestrogens
For contraception

Special considerations:
Low moisture content in vagina under normal physiological conditions
Vaginal microflora
Irritation
Leakage - stain clothing, fatty base not preferred

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13
Q

Suppository base requirements

A

Melt or dissolve in physiological fluids
Exhibit adequate volume contraction after solidification to enable easy removal in manufacture
Optimised viscosity on melting
* Pourable into the mould
Chemical and physical stability
Compatible with drug
Permit optimal drug release

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14
Q

Advantages and disadvantages of coca butter

A

Advantages
* Nontoxic and non-irritating
* Compatible with many drugs
* Melts too quickly at body temperature

Disadvantage
* Natural product - variable composition
* Low softening temperature, further lowered by drug incorporation
* Exhibit polymorphism beyond 35C
o Metastable states mp 18-28C
* Poor water absorption

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15
Q

Advantages and disadvantages of synthetic triglyceride bases

A

More widely used than theobroma
* Available with different mp to accommodate drugs that lower melting point of bases
* More stable and don’t exhibit polymorphism
* Properties can be modulated
o Add glycerol monostearate to improve water sorption
o Add tween 80 to reduce tendency to fracture

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16
Q

What are some water soluble/ miscible bases

A

Glycerin gelatin
Macrogols

Very high osmotic effects = laxatives

17
Q

Disadvantages of water soluble/ miscible bases

A
  • Hygroscopic
  • Preservatives required
  • Require moistening with water to reduce pain on insertion
  • Slow dissolution in rectum
  • PEGs incompatible with some drugs and containers
18
Q

Quality and compendial requirements for suppository

A

Appearance = smooth, uniform texture and appearance - colour and odour
Disintegration - Fat-based = 30mins, Water soluble base = 60mins
Uniformity of dosage units -
weight variation >25mg and >25% of total mass
content uniformity if drug if <25mg or 25% of total mass

19
Q

What are some advantages of aerosol formulations

A

Withdrawal of one portion does not contaminate or exposure remaining dosage form
Hermetic seal and opaque packaging
* Protection against oxygen, moisture, light and microbes
Dosage characteristics are preserved
Accurate dosing by metered valves
Can be applied without touching lesion - reduce irritaion and mechanical damage to lesions
Clean application

20
Q

Wat are the applications of aerosols

A

Nasal/ pulmonary delivery
Topical delivery
Rectal/ vaginal delivery

21
Q

What is the two phase system of aerosols

A

One liquid phase with liquefied propellants and drug formulation
Vapour phase - propellant

22
Q

What is the three phase system of aerosols

A

Two liquid phase with liquefied propellant and aqueous drug formulation
Vapour phase - propellant

23
Q

What is the compressed gas system

A

One liquid phase comprising drug formulation
Vapour phase - compressed inert gas - N2, CO2, N2O

24
Q

What are propellants

A

Comprise of gas that has been liquefied under high pressure below critical temperature in the canister
* When expelled it expands and vaporises to deliver drug formulation as a fine mist

HFA-134a
HFA-227

25
Q

What are dermatological aerosols used for

A

For solutions, emulsions, suspensions, powders and semisolids
Application of drugs to burns and open wounds
* Steroids
* Antibiotics
* Astringents

26
Q

What are rectal and vaginal aerosols used for

A

Delivery of estrogens, anti-inflammatory agents and drugs for contraception
Delivered as foams

27
Q

Nasal aerosols and sprays

A

Solutions or suspension formulations
Local or systemic action

28
Q

What are examples of pulmonary aerosols

A

MDI or pMDI
Dry powder inhalers
Nebilisers

29
Q

What are advantages and disavantages of MDI or pMDI

A

Advantages
* Portable and effective aerosol generator
* Low cost per dose
* Reproducible multidose delivery
* Canister protects against oxidative degradation and bacterial contamination
Disadvantages
* Drug BA is highly dependent on correct use by patients
* Inefficient drug delivery

30
Q

What are advantages and disavantages of dry powder inhalers

A

Advantages
* Breadth actuated
* Spacer not necessary
* Portable
Disadvantages
* Adequate inspiratory flow required
* May result in high pharyngeal deposition
* Drug delivery potentially affected by humidity

31
Q

What are nebulisers

A

Devices that transform drug solutions/ suspensions into aerosols
* Use mouthpiece or mask to deliver dose

32
Q

Advantages and disadvantes of spacers

A

Advantages
Enhance drug delivery - extend mouthpiece, direct drug spray towards mouth to reduce drug loss into air
Compensate for poor patient technique/ coordination
Reduce oropharyngeal drug deposition
* Smaller particles as they travel along spacer

Disadvantages
Bulky size
Regular cleaning to minimise bacterial contamination
Electrostatic charges reduce drug delivery

33
Q

What are aerodynamic equivalent diameter

A

Diameter of an equivalent sphere of unit density that has an identical settling velocity as the particle
* Equivalent to spherical drop of water with identical settling velosity
* Dependent on particle diameter, shape and density
* Determines site of deposition

34
Q

What are MMAD and GSD

A

Mass median aerodynamic diameter (MMAD) - d50%
* AED at which 50% of particles are larger and 50% are smaller

Geometric standard deviation (GSD) - spread of particle size

35
Q

Respirable dose and fraction

A

Inhalable fraction
* MMAD <100micron

Thoracic fraction
* MMAD 11.64micron
* GSD 1.5 micron

Respirable fraction
* MMAD 4.25micron
* GSD 1.5micron

36
Q

What are compendial requirements for aerosols

A

Dose or spray content uniformity throughout container life - mass per sungle dose
Droplet and drug particle size distribution
Spray pattern
Plume geometry
Priming and repriming - initial use and >24hrs or 7days
Tail off profile

MPharm (20 decks)

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