ADT Exam 1

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Major drug absorption takes place in
- small intestine
- high surface area
- large blood supply
Drug absorption pathways
- passive diffusion
- facilitated transport
- active transport
- phagocytosis/pinocytosis
Most drugs are absorbed via

passive diffusion
Absorption of the drug from the gut depends on
- gastric emptying
- intestinal motility
- mucosal surface area
- degradation of the drug in the stomach (pH)
- metabolizing enzymes in the gut
slows gastric emptying and motility
- food
- increased calories
do not want drug in stomach more than ___ min to avoid degredation from low pH

15 min
60% of drug delivery systems

Oral CR
Oral sustained and controlled release products
- avoids frequent dosing
- involves use of biodegradeable polymers
- can result in toxicity if dosing regimen not followed
tylenol sustained release could result in

liver toxicity
six types of oral controlled drug delivery
- physical
- chemical
- osmotic
- diffusion
- dissolution
- targeted
Goals of oral controlled release systems
- better control over systemic concentrations
- sustained level of drug after a single dose
- decrease pill burden
disadvantages of OCRS
- dose dumping can occur
- removal of drug from systemic circulation is impossible
- erratic or variable drug absorption
Physically controled drug delivery

altering absorption by altering viscosity of the formulation
Most soluble form to least soluble form
- solution
- suspension
- capsule
- tablet
- coated tablet
particle size with fastest absorption

small
Chemically modified drug delivery
- prodrugs
- salt forms
- esters
Osmotically controlled drug delivery (push-pull)
- drug embedded in polymer with a laser driven pore
- water comes in from the GIT and dissolves sugar, pushing drug solution through the delivery orafice
osmotically controlled drug delivery (L-oros)
- drug enclosed in soft gelatin capsule
- inner membrane
- osmotic push layer
- rate controlling membrane
- delivery orifice
Rate controlling membrane of L-OROS system
- membrane controlls how much water comes in
- ensures constant pressure for same release
OROS Tri-layer
- more for solids
- 2 drug compartments that have different release rates
- 1 push compartment
- rate controlling membrane
- overcoat
- delivery orifice
First once a day treatment for overactive bladder

Ditropan XL
dM/dt=K(A/h)(x)C_s
- the rate at which drug is pumped out of the osmotic system through orifice
- dM/dt = amount of drug in mg delivered per unit of time in hours
- Cs concentration of the saturated solution (constant)
- K membrane permeability (mg/hr)
- x is the osmotic pressure
The rate of drug release ____ until the excess undissolved drug is depleted

zero-order (constant)
Non-zero order release sets in when

the saturated concentration (Cs) becomes unsaturated
Advantages of OROS
- enhanced bioavailability
- patterned release
- reduced variability
Diffusion controlled system

drug diffuses through a matrix at a constant rate
polymers for diffusion (matrix) control
- PLGA
- PEG
- Polyacrylamide
- PVA
- xanthan and guar gums
typical commercial product that utilizes matrix diffusion

nifedipine er
Encapsulated dissolution controlled system

once coating is dissolved drug core is available for immediate release and absorption
control of encapsulated dissolution time
- thickness of polymeric membrane
- compressing multiple particles of varying thickness of drug
Examples of materials used for micro encapsulation
- cellulose
- shellac
- gelatin
- carnuba wax
dC/dt=k(A/V)(Cs-C)
- estimates drug release from dissolution controlled system
- dC = dissolution rate
- V = volume of solution
- k = dissolution rate constant
- A = surface area of exposed solid
Enteric coating of tablets are designed to release drug

in the small intestine or large intestine
coating that allows for release in large intestine

chitosan polymers

Author

Rx2013

107889

Card Set

ADT Exam 1

Description

Oral Controlled Release

Updated

2011-10-11T00:10:40Z

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