Lecture 16 - transdermal drug delivery 2 Flashcards
what is storage modulus vs loss modulus?
storage modulus is how much energy can be absorbed elastically or how solid-like is the gel
loss modulus is the energy that is dissipated as heat when the material behaves more like a viscous liquid, or how liquid-like the gel is.
what are different types of gel networks?
Polymer Gel with Covalent Crosslinks
Polymer Gel with Micro-crystallites
Polymer Gel with Stacked Double Helices
Polymer Gel with Stacked Triple Helices
Polymer Gel with “Egg-box” Junction
Particle Gel with Fractal Aggregates
what are polymeric gels
Macromolecular gelators.
natural - gelatine, agarose and alginate
synthetic - polyethylene and carbomer
The gels can be set through physical stimulus (temperature, ions solvents and can dissolve or erode) or synthetic or cross-linking (cross-linking stable gels can reselt in them beign swelled)
can be sesntiive to chemicals, solvents, ions etc.
what are applications of gels in products ?
polythene in hydrogel sheets
carbomer 980 and carbomer copolymer
testin 50mg gel - for testosteroen
voltarol pain relief gel
discuss particle gels
House-of-cards Structure:
These gels are formed by clays like bentonite.
String-of-pearls Structure:
Composed of fumed silica (e.g., Aerosil®) or aluminium oxide
Particle gels are solvent-independent, meaning they can form hydrogels and oleogels without the need for cross-linking.
They do not need a physical stimulus to gel but rather rely on a setting time.
Compared to polymeric gels, particle gels demonstrate sensitivity to ions, although to a lesser extent
what does the trend of a transdermal patch show ?
The graph demonstrates that the concentration of drug from the transdermal system quickly reaches a peak and then maintains a relatively stable concentration over time, while the concentration from the oral tablet has a quicker drop-off.
describe the drug in adhesive patch
drug in adhesive patch has a backing layer, drug in adhesive and release liner
it has a diffusion control drug release. the drug in polymer metric is surrounded by the adhesive or drug dispersed directly in adhesive layer.
The release rate is not constant; it follows a non-zero order kinetics, meaning the rate of release changes over time.
The release rate slows down as time passes. (t^0.5),
describe a matrix dispersion type patch
backing layer, drug in matrix, adhesive and removable release liner.
drug diffusion from the matrix
describe a reservoir patch
backing layer, drug reservoir, membrane, pressure sensitive adhesive, and release liner
Polymer Membrane Permeation Controlled: The rate at which the drug permeates through the patch is controlled by the polymer membrane.
Constant Release Rate: The drug is released at a constant rate over time.
Zero Order Kinetics: The release mechanism of the patch is designed to be zero order, which means the drug is delivered at a constant rate regardless of concentration.
describe the different layers of transdermal patches and their properties
Adhesives:
- They ensure the patch sticks to the skin for its intended lifetime.
- Should be non-irritant and non-allergenic.
- Must be compatible with the drug contained in the patch.
- Designed to allow for painless removal.
- Common materials used include polymers such as polyacrylates, polyisobutylene, or polysiloxane
Backing Layer:
- This layer must be stretchable to accommodate body movement.
- It can be occlusive for short-term patches and is often made of polyethylene or polyester.
- For other types of patches, PVC (polyvinyl chloride) may be used
Matrix/Reservoir:
The drug can be either dissolved in the polymer or added as a suspension within the matrix or reservoir.
The viscosity of the polymer can be controlled by cross-linking.
where are application sites of buprenorphine and rivastigamine patches ?
buprenorphine patches - upper outer arm, upper chest, upper back, side of the chest
rivastigamine patches - side, front, back,
describe 2 novel delivery systems for drugs
Iontophoresis:
This technique uses an electrical current to drive charged drug molecules through the skin. iontophoresis involves the use of a drug electrode and a counter electrode to facilitate drug delivery. It highlights the mechanisms and factors affecting drug transport and indicates that both small and large molecules can be delivered using this method.
describe electroporation
electroporation
electroporation involves the application of an electric field to the skin, creating temporary pores in cell membranes which can facilitate the entry of drugs.with a power supply and pulse electrode, indicating that a controlled electrical pulse is applied to an area where a drug formulation is present on the skin.
This method is generally used to enhance the penetration of drugs or other molecules into cells or through the skin
describe sonophoresis
Sonophoresis:
This method uses ultrasonic waves to increase the permeability of the skin and enhance the delivery of medications across the dermal layer.
The diagram shows an ultrasonic transducer placed over the skin, with an applied formulation underneath it, indicating that the sound waves facilitate the drug’s penetration into the skin
describe needless injection system
A needleless injection system is depicted, which is a way to deliver drugs into the skin without the use of traditional needles.
It typically uses a high-pressure jet to deliver the medication directly through the skin.
