Modified release Flashcards
why are modified release dosage forms used over conventional immediate release?
- delivering drug at a specific rate/time
- extending the drug release over a specific duration
- delaying drug release to a pre-determined time point
why would we delay a drug release to a pre-determined time point
to target a drug release to a specific area or avoid drug release in a specific area
what are the types of modified releases
- Extended release
- sustained release
- controlled release
- long acting - delayed release
- site specific targeting
- enteric coating (protecting the stomach from the drug or the drug from the stomach)
what are the advantages of extended release?
- more stable plasma concentration than immediate release
- reduced dosing frequency
- better pt compliance and adherence
- chronotherapy - administring a drug related to the body rhythm e.g. circadian rhthym
Immediate release is the dosage form with the HIGHEST/LOWEST drug plasma conc?
Highest
whats advantage does MR have over IR?
less side effects
what is the most common design for delayed release? why?
enteric coating as it is pH sensitive
why are delayed release dosage forms used?
to release in other locations than the stomach, this means that the enteric coating must protect acid liabile drugs
MR advantages
- cost effective
- better compliance
- lower frequency of administration
- reduced side effects
what are the different types of MR kinetics?
- zero order
- first order
- higuchi
what is zero order release?
where the rate of drug release is independent of the concentrations of drug in the dosage form, which has a CONSTANT drug release.
what happens to the kinetics of a drug that follow zero order? and why?
they follow zero order til the next dosing interval, the drug concentrations depletes, therefore changing the release profile into the first order
what kinetic order has the best control over the drug plasma concentration?
zero order
what order of kinetics does controlled release formulations have?
zero order
whats the equation of drug release with zero order?
what are some examples of zero order formulation designs?
- osmotic systems
- matrix tablets with poorly soluble drugs
- reservoir systems
what is first order release?
the rate of drug release is dependent on the concentration of the drug in dosage form.
there is a rapid initial drug release, followed by a decline in release rate. the release rate slows as the concentration of the drug decreases
what kind of kinetics does sustained release follow?
first order release
what are examples of first order formulation designs?
- conventional tablets
- water soluble drugs in a porous matrix system
what is the higuchi release profile?
the longer the distance the drug molecule has to travel the longer the time for the drug to be released from the matrix system
what is to consider about the MR formulation?
- GI transit time
- pt convenience and ability to use product as directed
why is it important to counsel your patient on MR formulations? how?
to make sure they do not crush etc. so that the release profile for the drug remains intact so subtherapeutic effects are felt.
by making sure the pt is comfortable using the drug or may prefer an alternate formulation
what are the release mechanisms of ER formulations?
- dissoultion controlled formulations
- diffusion controlled formulations
- osmotically controlled formulations
- ion exchange systems formulations
what is dissolution controlled formulations controlled by ?
Noyes Whitney, therefore, …
what formulation is extended release?
multiunit particluate systems (MUPS)
what formulation is used in delayed release?
MUPS or tablet with an enteric coating to prevent dissolution within the stomach
What is multi-unit particulate systems? what is the significance?
the use of different concentration of polymers within the drug.
the lower the concentration of polymers the faster the dissolution
how is flux calculated?
what are the two types of systems diffusion controlled dosage forms used?
- matrix systems
- reservoir systems
what are matrix systems and the type of kinetics involved?
drug evenly dispersed within a polymer matrix = zero order.
a change in conc. gradient causes first order kinetics
a change in diffusion distance causes higuchi release
what are reservoir systems? and relation to kinetics order
a drug present in the core of a semi-permeable membrane. a constant conc. gradient = zero order
why are reservoir systems zero order?
as the drug releases is from one point (one exit way) therefore there is a constant amount of drug release as the gradient will remain the same due to the constant drug concentration on the outer layer ready to diffuse out.
what are examples of matrix systems?
- insoluble polymer matrix
- soluble (erodible) polymer matrix
- soluble (swellable) polymer matrix
- lipid matrix