modified release 1+2 Flashcards
what is a modified release dosage form?
Dosage forms that contain special excipients or are prepared by a special process designed to modify the rate, the place or the time at which the active substance(s) are released
what are the different types of immediate release dosage units?
-disintegrating/ chewable/ effervescent/ sublingual/ buccal
what are the different types of modified release tablets?
delayed release repeated release prolonged release sustained release extended release controlled release modified release
how does repeat action and modified release dosage form compare?
modified release- constant between MEC and MSC
repeated action- spikes- up and down- risk of under or over dosing
what are some of the advantages of MR?
•Improved treatment of chronic illnesses–
Steady plasma concentration between MEC and MSC –Reduction in systemic side effects
•Reduction in dosage frequency
improved patient compliance
what are some of the limitations of MR dosage forms?
GI tract physiology
require drug properties
possibility of overdose due to dose dumping
what are the selection criterial for MR formulations?
optimum water solubility - 10mg/mL if diffused controlled system
ideal half life= 4-6hr
wide absorption window
low first pass metabolism
what does a low half life (less than one hour) and a high half life ( more than 6 hours) mean?
low= need for high doses high= slow elimination and potential toxicity
what are the 4 classifications of the biopharmaceutical classification system?
- High solubility & high permeability (best for MR) e.g. propranolol
- Low solubility and high permeability e.g. ketoprofen, carbamazepine
- High solubility and low permeability e.g. ranitidine, atenolol
- Low solubility and low permeability (not for MR) e.g. frusemide, hydrochlorothiazide
what is high and low solubility?
high= highest dose strength is greater than or equal to 250ml of aq media over ph 1-8 low= highest dose strength is soluble in less than or equal to 250ml of aq media over ph 1-8 or less than 1mg/ml
what is high and low permeability?
high permeabillity= more than 90% if administratered dose is absorbed in vivo
low= less than 20% of administered dose is absorbed in vivo
how do you determine the apparent drug permeability?
-Caco2 cell lines
resembles cells of the small intestine
At regular time intervals the drug concentration at the receiver chamber is determined
Papp=dQ/dt(1/CoA)
what is the different mechanisms of drug released from MR tablets?
diffusion controlled release
dissolution controlled release
erosion- controlled release
osmosis- controlled release
what is diffusion controlled release?
- GI fluids dissolve the drug
- Dissolved drug molecules diffuse out of the dosage form via 1-pores of the release unit or 2- the surrounding membrane
what is dissolution-controlled release?
-it can be achieved by:
sparingly water sol drug
slowly dissolving carrier
slowly dissolving coating or ph dependent coating
-pulsatile release and delayed release tablets
what is erosion controlled release?
- matrix is gradually liberated from dosage unit surface exposing the drug to the GI fluids
what is osmosis-controlled release?
osmotic pump systems
what is a hydrophillic colloid matrix?
- Swellable‐soluble matrix systems
- Drug
- Water‐swellable hydrophilic polymer
what is the initial burst effect of a surface drug?- from hydrophilic matrix
initial bit released
Polymer swelling and dissolution are synchronised
•Constant thickness of gel layer
•Zero‐order release