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Drug Release 1
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46
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10/02/2009

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Term
What are the Factors Affecting Drug Release
Definition
• Order of reaction
• Formulation factors
• Physicochemical parameters
• Physiological factors
Term
Define Zero order
Definition
When rate of release is independent of concentration and constant over time
 C = -k0t + Co
 T1/2 = ½(C0/k0)
Term
Define first order
Definition
When rate of drug release is directly proportional to concentration remaining with time. ln C = - kt + ln Co
 T1/2 = 0.693/k
Term
What are 2 types of release systems?
Definition
Immediate release or sustained release
Term
What are the formulation factors?
Definition
type of release system
Type of dosage form
– Solid or liquid
– Route of delivery
Term
Define Immediate Release Systems
Definition
• Dosage forms that are designed to disintegrate and release their medication with no special rate controlling feature
Term
What time of release system is Instantly Disintegrating Tablets? HOw fast do they dissolve?
Definition
Immediate Release Systems, 10 s to 1 m
Term
Define Modified release dosage forms
Definition
Include dosage forms having drug release feature based on time course and location.
Term
Why were Modified release dosage forms created?
Definition
Designed to achieve convenience and therapeutic objectives not offered by conventional or immediate release dosage forms.
Term
Define and list type for Sustained Release Dosage Forms:
Definition
Dosage forms that provide medication over an extended time, Modified release dosage form
Term
Define and list type for Controlled release dosage forms
Definition
– These products are designed to release their medication in a controlled manner, at a predetermined rate, duration and location to achieve and maintain optimum therapeutic blood level of the drug
Term
________ _________ dosage form allows at least a two-fold reduction in dosing frequency as compared to their conventional dosage forms
Definition
Extended release
Term
Define and list type of form for Repeat action
Definition
– Contains multiple doses of medication within same dosage form
– Each dose is released at a fixed interval
– E.g. Two layered tablets are prepared with one layer of drug for immediate release with the second layer designed to release the drug later either as a second dose or in an extended release manner, Controlled release dosage forms
Term
Define and describe Chrono-Controlled Release
Definition
– A chrono-controlled release reflects the circadian rhythm of the patient.
– The drug release directly corresponds to the need of the patient, so when the condition of the disease is at its worst, blood concentrations of the drug is at it's peak
Term
Define Site- Specific and Targeted Release
Definition
Drugs are released to localized regions or at a specific site
Term
Define Bio-responsive release
Definition
he delivery system release drug in response to a biological stimulus. For example, blood glucose levels trigger release of insulin from a drug delivery device.
Term
Define Variable release
Definition
The delivery system releases drug at a variable rate to match with endogenous circadian rhythms or mimics biological rhythms.
Term
Define Pulsatile Release
Definition
– “Pulsatile release system enables immediate drug release in pulses that are separated by a defined time delay. This type of profile is beneficial when the intensity of a disease varies in a circadian rhythm fashion”
Term
Define Modulated/self-regulated release
Definition
– This type of system delivers necessary amount of drug under the control of a patient
Term
Describe and give an example of Delayed release dosage forms:
Definition
– Does not release drug immediately
– Maintain drug within dosage form for some time before releasing
– Time based or environmental effect like gastrointestinal pH
– Example: Enteric coated tablets
Term
The design of rate-controlled dosage forms is ________upon the unique characteristics of individual drugs
Definition
dependent
Term
Important aspects of the drug include ...
Definition
physical, chemical and biological properties
Term
For a sustained release product to maintain a constant drug level in the body, the drug must be released from the dosage form at a rate that will replace the amount of drug_____ through _____and ________
Definition
lost,metabolism ,excretion
Term
Principles that control Rate of Release
Definition
 Diffusion-controlled release mechanism
 Dissolution controlled
 Osmosis controlled
 Mechanical controlled
 Bio-responsive controlled
Term
In diffusion controlled delivery system, the drug diffuses through a ...
Definition
polymeric membrane, polymeric or lipid matrix.
Term
Diffusion controlled devices could be of two types:
Definition
Matrix device or Reservoir devices:
Term
Describe Reservoir devices
Definition
– Pharmacological agent (drug) forms a core surrounded by an inert diffusion barrier (membrane)
-Membrane could be non-porous or microporous
Term
Describe Matrix devices (also known as monolithic devices):
Definition
Drug is dispersed or dissolved in an inert polymer or lipid.
Term
In Dissolution-controlled Release Mechanisms drug release is controlled by controlling the ...
Definition
dissolution rate of a polymer.
Term
Dissolution controlled devices could also be of two types:
Definition
– Dissolution-controlled reservoir devices
– Dissolution-controlled matrix devices
Term
In Dissolution-Controlled Reservoir Devices drug is retained by a polymeric membrane and after certain period of time ...
Definition
polymeric membrane dissolves and releases the drug.
Term
In dissolution controlled reservoir devices, the drug release is controlled by the ______ and/or the ________ ________of the polymeric membrane surrounding the drug core.
Definition
thickness, dissolution rate
Term
In dissolution controlled reservoir devices once the coating polymer is dissolved, the drug undergoes ________ and _________
Definition
dissolution and absorption.
Term
Drug cores can be coated with polymers of different coating _______, so that drug release can be delayed for certain periods, e.g. 2, 4, 6 and 8 hrs.
Definition
thickness
Term
Coated drug can be placed in ________ or compressed into _______
Definition
capsules, tablets.
Term
Drug release is controlled by dissolution of the ...
Definition
matrix
Term
As the size of the matrix decreases with the process of dissolution, the amount of drug release ...
Definition
decreases
Term
The decrease in drug release can be compensated by manipulating the ...
Definition
polymeric matrix
Term
The movement of water results in the _______ in pressure in the solution and the resulting osmotic pressure can be used to pump out a drug from the delivery system.
Definition
increase
Term
The _________ and _________ parameters can be controlled in order to achieve zero order release.
Definition
device and formulation
Term
Since Osmosis Controlled Drug Release devices require osmotic pressure to be effective, the device operates essentially ________ of the environment
Definition
independent
Term
In Bio-responsive Controlled Release delivery systems, drug release can be controlled by ...
Definition
external environment
Term
In Bio-responsive Controlled Release devices the drug release can be controlled by controlling the ...
Definition
pH and ionic strength
Term
pH can affect the________ of a polymeric membrane and is often called what type of release system?
Definition
swellability, swelling-controlled release systems
Term
In swelling-controlled release systems are initially____, when placed in the body, will absorb water or will come in contact with a certain pH and swell.
Definition
dry
Term
In swelling-controlled release systems swelling _______water content of the formulation as well as the polymeric ______ _________
Definition
increases ,mesh size.