Exam 5 Spring 2017 Flashcards
What dosage forms are the only ones that you can use with controlled drug delivery (CDD)?
- tablets
- capsules
What are the types of controlled drug delivery (CDD)?
XL, SR, ER, CR, PA, PL, SA, TR
What are CDD useful for?
to treat chronic diseases
What is dose dumping?
when the CDD fails and delivers the amount of drug in the tablet all at once
Define CDD
drug system that is capable of spatial placement and temporal release of a drug
What does spatial placement pertain to?
release of drug in a particular location
What does temporal placement pertain to?
time release of the drug
What are the ways in which you can maintain sustained plasma levels of the drug?
- multiple dosing
- intermittent infusion
- constant infusion
After how many half lives can we assume that the drug is out of the body?
- four
- some literature use 3.3 because that equals 90%
intermittent infusion
drug is given continually but not continuously
multiple dosing
- requires strict adherence
- cannot tolerate missed doses
- if doses are missed, plasma levels not sustained and may fall below MEC
What is the assumption for CDD?
kinetics of drug release governs drug availability
What are the types of CDD systems?
- osmotically controlled
- swelling controlled
- diffusion controlled
- dissolution controlled
- ion-exchange resin
- complex formation
- magnetically controlled
- electrically controlled
osmotically controlled system
- has a hole in the tablet
- polymer is semi-permeable
- pH independent
With respect to osmotically controlled systems, what does it mean that the polymer is semi-permeable?
water and GI fluids can enter tablet but not permeable to substances coming out of tablet
example(s) of osmotic agents
- mannitol
- xylitol
What is osmotically controlled systems dependent on?
- size of hole
- type of polymer
- type of osmotic agent / osmotic pressure
- saturated solubility of drug
Example(s) of semi-permeable membranes used to regulate osmotic permeation of water
- cellulose derivatives
- polyvinyl chloride
- polyvinyl alcohol
How does the osmotic agent play a role in osmotically controlled systems?
- osmotic agent creates a high osmotic pressure gradient inside the tablet
- fluid enters the tablet (osmosis)
- increase in volume -> drug gets pushed out of hole
swelling controlled system
- polymer and drug tightly packed
- once in GIT, polymer swells to release drug
In a swelling controlled system, what is the release of drug dependent on?
rate of water sorption in polymer
Example(s) of polymers used in swelling controlled systems
- poly acrylic acid
- sodium alginate
- cellulose derivatives
diffusion controlled system
polymer is physical barrier to drug release
In a diffusion controlled system, what is the release of drug dependent on?
- nature of polymer
- thickness of polymer
What are the categories of diffusion controlled systems?
- reservoir
- matrix
describe the reservoir diffusion controlled systems
- drug is coated with water-insoluble polymer
- water penetrate through polymer to reach drug
- drug dissolved to produce saturated solution
- saturated solution diffuses through polymer to outside
If the polymer for reservoir diffusion controlled system is water-insoluble, how does the drug diffuse through it to the outside?
osmotic movement through polyemeric mesh (space between macromolecular chains)
For reservoir diffusion controlled systems, how can release of drug remain constant?
if concentration of drug in the core remains at saturation
describe the matrix diffusion controlled systems
- aka monolithic
- drug dispersed in polymeric matrix
Polymers for diffusion controlled systems
- reservoir’s polymers are water-INsoluble
- matrix’s can be both
fate of polymers for matrix diffusion controlled systems
- erode with tiem
- dissolve
- stay intact as ghost matrix
dissolution controlled system
dissolution of drug is the major role in drug release