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Ceutics II - Exam 4 (Controlled release)

Terms in this set (24)

top 3= IV
Constant infusion
Multiple IV doses
Intermittent infusions

Last = oral
What routes of admin are each of these drug profiles?
Increase efficacy
Reducing dosing frequency
Increase patient compliance
Can decrease the cost of treatment for some chronic diseases
Advantages of controlled drug delivery
the kinetics of the drug release - rather than the kinetics of the drug absorption
What governs the ability of the drug in a controlled deliver system?
Osmotically controlled
Swelling controlled
Diffusion controlled
Dissolution controlled
Ion exchange resin
Complex formation
Types of controlled release systems
-Not suitable for all drugs
-Not all medical conditions need it
-Dissolution & absorption of released drug should be predictable
-Rate of drug release from dosage form is precisely controlled
-Ideally (but not feasible) the rate of drug release should be equal to the rate of elimination from body
Characteristics of controlled release systems
-Neither slow nor fast absorption/elimination rates
-Should be uniformly absorbed from the GIT
-Effective dose should be small
-Posses a good margin on safety
-Used in treatment of chronic rather an acute conditions
Ideal drug candidates for controlled release systems
-Dose dumping
-Once administered, termination of therapy is not easy
-erratic or variable release from dosage form
-Absorption of released drug may not be a constant phenomenon
-Delayed release may delay the immdiate effect of drug
Limitations of controlled release systems
shortest
to reduce frequency of dosing
In a controlled release system you want to pick a drug with the shortest/longest half-life?
Magnetically & electrically controlled systems
What delivery systems are currently being researched for use in control release?
Drug substance when chemically combined with certain chemical agents form complexes that may be only slowly soluble in GI fluid (depending of pH of environment) - slow dissolution rate provides the extended release
How does complex formation work as a controlled release system?
Salts of tannic acid (tannates)

Dytan-CS
Rynatan
Depakote ER
What are examples of complex formation controlled release systems?
Tussionex Pennkinetic ER
Ionamin
Phentermine
Examples of ion exchange resin controlled release systems
A solution of cationic/anionic drug is passed through a column containing an ion exchange resin... H+ atoms of the resin are replaced by cationic drug & OH- groups are replaced by anionic drug

Drug releases from the resinate depending on the pH & electrolyte concentration in the GIT
How does Ion exchange resin work as a controlled release system?
Solubility of the drug
What is considered the rate limiting step in dissolution controlled release systems?
Calan SR caplet
Ambien CR
Isoptin SR
Examples of drugs based on the matrix diffusion controlled release system
When polymer coating is water soluble - dissolution & drug release will continue until everything is dissolved

When the polymer is water insoluble The drug solution will be released from the middle - but there will be a "ghost matrix" left behind
What is the difference between using water soluble vs. insoluble polymers in the formation of a matrix (Diffusion controlled delivery systems)?
Diffusion
What is the rate limiting step in diffusion controlled delivery systems?
Diffusion controlled release system
The polymer functions as a physical barrier to drug release - Follows Fick's law of diffusion
Diffusion controlled - resivoir
The drug core is encased by a water-insoluble polymer - there are two distinct compartments for drug & polymer -- when water penetrates the polymer the drug dissolves to produce a saturated solution & diffuses through the polymeric mesh
Swelling controlled system

(once swollen the release of drug is rapid)
This system involves the use of hydrophilic polymers or hydrogels to control the release of drug - Drug and polymer are mixed together - the formulation absorbs water and swells to release the drug
Poly acrylic acid
Sodium alginate
Cellulose derivatives
Examples of polymeric materials used in swelling controlled systems
-Consists of a core containing drug alone/or together with an osmotic agent (NaCl)
-Tablet is coated by a semi permeable polymer membrane w orifice for drug release
-Brings fluid into tablet - and once pressure is built up the drug solution is pushed out of orifice
Characteristics of osmotically controlled release systems
Saturated solubility of drug
osmotic pressure
size of the orifice
type of semi permeable membrane used


(The drug release rate is unaffected by pH of the environment)
Factors which affect drug crease from the osmotically controlled system are:
Procardia XL (Nifedipine)
Calan SR (Verapamil)
Glucotrol XL (glipizide)
Minipress XL (Prazosin)
Volmax (albuterol)
Examples of osmotically controlled release systems:
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