Dosage Forms Exam 3 Flashcards
What are the two types of controlled drug delivery?
Temporal (time of release)
Spatial (location of drug)
What are the types of drug release control mechanisms?
Diffusion-controlled Dissolution-controlled Erosion-controlled Osmotic systems Swelling systems
What are the types of diffusion-controlled systems?
Reservoir Devices
Matrix Devices
What controls release rate in a reservoir system?
Membrane surrounding the rug reservoir
What controls release rate in a matrix system?
The matrix that the drug is mixed in with
What type of delivery system is Ocusert?
Drug reservoir (has a membrane around reservoir)
What is the purpose of the annular ring in Ocusert?
It makes it visible (opaque)
What type of polymer is Ocusert made of?
EVA
What type of release mechanism is used in tetracycline periodontal fiber?
Drug Reservoir
What is the polymer in tetracycline periodontal fibers?
Cellulose acetate
What is Norplant?
Subdermal implant contraceptive (levonorgestrel)
What polymer is used for Norplant?
Silicone
What is the formula for Drug release from a diffusion-reservoir system?
M = DSKCst/h
What variables are changing in the diffusion system reservoir formula?
M = kt
What does the graph for a diffusion-reservoir release look like?
A diagonal line
What does the graph for the rate of release of a diffusion reservoir system look like?
Straight line (constant release rate over time)
What does M mean?
Amount of drug passing through membrane
What does D mean?
Diffusion coefficient
What does S mean?
Cross section area
What does K mean?
Partition coefficient of the membrane
What does Cs mean?
drug concentration in reservoir (stays constant b/c drug moves closer to fill the space after some drug diffuses out)
What does h mean?
Thickness of the membrane
What does drug release depend on in a diffusion-matrix system?
The device geometry
What is the simplified equation for drug release from a diffusion matrix?
M = kt^(1/2)
What is Cd?
Total drug concentration (dispersed + dissolved drug)
What is Cs in a diffusion-matrix system?
Solubility of the drug in the polymer
What is the shape of the M curve in a diffusion-matrix?
It is a hyperbole (releases a lot at first, and then fairly small amount)
What is the release rate of the diffusion-matrix?
Releases rate is high at first and then decreases with time
What type of controlled release does Nexplanon/Implanon NXT have?
matrix/coating
How long can Nexplanon/Implanon be used for?
Up to 3 years
What polymer is used in Nexplanon/Implanon NXT?
Ethylene vinyl acetate
What are the two types of dissolution system?
Encapsulated (similar to reservoir diffusion system) and Matrix
What is the formula for a dissolution-matrix drug release?
M = DS(deltaC)t/h
What is Delta C?
Cs-C
What variable changes in the Dissolution-Matrix equation (besides t)
S–surface area gets smaller as more of the drug dissolves
What is the shape of the dissolution-Matrix drug curve?
It starts out as a straight line (constant release) and then tapers down to a steady concentration
What are osmotic delivery systems?
They have a film coating that is permeable to water and not drugs, and resistant to hydrostatic pressure
How do osmotic delivery systems work?
Water fills the membrane and increases hydrostatic pressure, which pushes the drug out of orifices that it is permeable through
What is an example of an osmotic delivery drug?
Concerta (Methylphenidate)
What is the formula for drug release from osmotic systems?
M = (kS/h)(delta pi) Cst
What is delta pi?
The osmotic pressure difference
What is k?
Membrane permeability to water
What is added to the equation if the drug also has a membrane that releases drug through simple diffusion?
DSKCst/h
like a Reservoir diffusion system
What is the equation of dM/dt for diffusion matrix systems?
dM/dt = (1/2)k(1/t^1/2)
What is the shape of a graph for an osmotic system?
Diagonal line
What is the shape of the graph of release rate for an osmotic system?
Straight line
How do erosion-controlled systems work?
The initial release is very slow, from the surface of the drug/pores in the matrix–like diffusion controlled system. The sustained-release depends on the erosion of the polymer–as it degrades, it begins to behave like a dissolution controlled system
What are some erosion-controlled systems?
Zoladex Lupron Nutropin Gliadel Wafer Sustol
What type of dosage forms to erosion-controlled systems come in?
Gel, injections (particles), wafers
What is an indication for gliadel wafer?
Put after a tumor is removed to prevent its further growth
What is BCNU?
Active ingriedient in Gliadel wafer–it has a short half life, but is slowly released to overcome though (manages residual tumor growth)
What polyanhydrides are found in the gliadel wafer?
PCPP-SA or PCPP
Which polyanhydride (PCPP or PCPP-SA) degrades faster in water?
PCPP-SA (higher ratios of SA degrade the fastest)
Which is more hydrophilic–PSPP or SA?
SA
Why is systemic administration of gliadel wafer not good?
It causes bone marrow suppression and pulmonary fibrosis
Do gliadal wafers exhibit temporal or spatial control?
Both
What is Lupron Depot used to treat?
Prostate cancer
What polymer is in Lupron Depot?
Poly(lactic-co-glycolic acid)
How long is lupron depot released over?
1-4 months
What is PLGA?
Poly(lactic-co-glycolic acids)
What are the two parts of PLGA?
Glycolic acid and lactic acid
Does a greater ratio of lactic acid or glycolic acid have faster degradation?
Glycolide
If two drugs have the same ratio of lactide to glycolide, does a more or less viscuous drug last longer?
More viscuous
If two drugs have the same ratio of lactide to glycolide will a higher or lower MW degrade faster?
lower
What are the properties of the longest acting poly(lactic-co-glycolic acid)s?
They have a high lactide to glycolide ratio and a high molecular weight/viscosity
If a polymer has a low Tg is it going to be solid or liquid at room temperature?
Liquid (and injectable)
What is an important property for Sustol Extended Release injection
Low Tg (liquid + injectable at room temperature)
How does a swelling-controlled system work?
The polymer swells, increasing the length of diffusion pathways which decreases drug concentration gradients and decreases the drug release rate
How could sewlling-controlled systems increase drug release rate?
Mesh size of polymer network increases, which increases drug diffusivities in the polymer network, which increases drug release rate
How can hydrolysis be used in controlled drug delivery systems?
A drug is covalently bound to a matrix former via hydrolyzable bondings–the rate of hydrolysis determines the rate of drug release through the polymer
What features decrease the side effects of inhaled fluticasone?
- Low bioavailability (first-pass effect)
- Binds plasma protein (99%_
What age can take inhaled fluticasone?
1yo
What is the absolute bioavailability of inhaled fluticasone
~10%
What is the alveoli surface area?
50-100 m^2
Does inhaled insulin powder have a faster or slower onset than subq?
Faster
What is the first inhaled insulin powder?
Exubera
Is Exubera still being sold?
No
What are the 4 regions of the respiratory tract?
Extrathoracic region (head and neck)
Upper bronchial region (Trachea and bronchi)
Lower bronchial region (bronchioles)
Alveolar region (nonciliated thoracic airways and airspaces)
What is inertial transport?
Driven by momentum
Increases with particle velocity, diameter, and density
Extrathoracic region of lungs
What is diffusional transport?
- Ultrafine particles
- Lung periphery (alveoli)
- Tend to be exhaled without depositing
What is gravitational transport?
(sedimentation)
Particles >0.1 micrometer
Increase with diameter and density
Bronchial region/alveolar region
What are the three particle deposition mechanisms?
Inertial transport
Gravitational transport
Diffusional Transport
What factors determine particle sedimentation velocity?
- Density of particles
- Acceleration from gravity
- Volume diameters
- Slip correction factors
- Shape factors (fibers, elongated particles, needles, spheres)
- Viscosity of fluid (air)
What is aerodynamic diameter?
Geometric diameter of a particle with a unit mass density (1g/cm3) that would settle at the same velocity as the particle of interest
What is the formula for aerodynaimic diameter (Dae)
(Pp)^0.5D
Where will particles 1-5 micrometers deposit?
Lower airways
Where will particles >5 micrometers deposit?
Upper airways (from inertial impaction)
Where will particles with aerodynamic sizes <1 micrometer deposit?
They may be exhaled
What are challenges in pulmonary drug delivery in the upper airways?
Filtering mechanisms from the nasal cavity trap and eliminate particles
What reflexes in the upper airways pose challenges to pulmonary drug delivery?
Sneezing and coughing
What poses challenges in conducting airways (lung airways) to pulmonary drug delivery?
Mucociliary escalator
IgA (antibody produced by plasma cells in the submucosa)
What challenges are there in drug delivery in alveoli?
Alveolar macrophages Immunologic mechanisms (T&B lymphocytes, IgG)