Modified release oral drug delivery Flashcards
What are the advantages of modified release drugs?
Peaks and troughs are minimised, Improved compliance, Lower side effects, less drug used
What is meant by a delayed release formulation?
The drug is not released immediately, but at a later time
What is meant by a repeat action delivery system?
A dose is released on administration, second and third doses are released at later intervals
What is meant by a prolonged release delivery system?
The drug is absorbed over a longer period of time than from a conventional dosage form.
What is meant by a sustained action delivery system?
An initial release of drug that is sufficient to provide a therapeutic dose soon after administration, then a gradual release over an extended period
What is meant by an extended release drug delivery system?
Slow release of the drug
What is meant by controlled release of the drug?
Release of drug at a constant rate and provides plasma concentrations that remain invariant with time
What types of dosage forms are there?
single unit, multiple unit, modified release
What types of dosage form leave the stomach rapidly?
solution and pellets
How long can single unit doses stay in the stomach for?
10 hours if delivery system taken with heavy meal
The intestinal transit time is approx. how long?
3 hours
Which factors make it difficult to achieve ideal drug release rates and constant plasma levels?
Variable physiological conditions of GIT
Clearance rate can be patient dependent e.g. age, race, etc
Disease status
Food/diet intake
What is the ideal BCS classification of a drug?
Class I with high solubility and high permeability
How do MR formulations provide slow release of maintenance dose?
Embedding drug into a wax or plastic matrix, incorporation in an osmotic pump, microencapsulation, chemical binding to ion exchange resin
Which headings are MR oral delivery systems grouped under?
monolithic/matrix systems, reservoir or membrane controlled systems
What is the difference between drug release from a hydrophilic matrix and a membrane controlled delivery system?
In a hydrophilic matrix, the colloids swell in contact with water to form a hydrated matrix which controls the further diffusion of water into the matrix and this controls the rate of release of drug. In a membrane controlled delivery system, there is no swelling on hydration of the membrane and the membrane does not erode.
How do osmotically-controlled systems work?
Osmotic pressure is used as the driving force to generate a constant rate of drug release. The membrane permits the passage of GI fluid, but not drug or electrolyte
In an osmotically-controlled system, what is the rate of drug release governed by?
The rate at which water is able to pass through the membrane and how fast drug solution can pass out
First order release is what you want to achieve with modified release systems. True or false?
False
Zero order
The main purpose of using an oral delayed release tablet is to prolong the half-life of a drug. True or false?
False
To provide site specific absorption of drug
How does microencapsulation alter the release of tablet?
Simply coating (e.g. by spray) the surface of a drug particles with polymer to slow down water penetration and hence dissolution
How do ion exchange resins alter the release of drugs?
Ionised drug binds to a polymeric resin through opposite charges. Drug resin is then milled to obtain a smaller particle size
Which ion exchange resins do basic drugs bind to?
Cationic exchange resins
Which ion exchange resins do acidic drugs bind to?
Anionic exchange resins
How do KCl extended release tablets work?
Each crystal of KCl is microencapsulated with an insoluble polymeric semi-permeable membrane. As fluids pass through the membrane KCl dissolves within the microcapsules and is released through the membrane over 8-10 hours
Which causes more gastric irritation slowK or MicroK?
SlowK
How do MST continus suspension granules work?
Morphine bound to ion exchange resin beads. Morphine is displaced by sodium and potassium ions present throughout the GIT
