ADT Exam 1

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ADT Exam 1
2011-10-10 20:10:40
Oral Controlled Release

Oral Controlled Release
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  1. Major drug absorption takes place in
    • small intestine
    • high surface area
    • large blood supply
  2. Drug absorption pathways
    • passive diffusion
    • facilitated transport
    • active transport
    • phagocytosis/pinocytosis
  3. Most drugs are absorbed via
    passive diffusion
  4. 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
  5. slows gastric emptying and motility
    • food
    • increased calories
  6. do not want drug in stomach more than ___ min to avoid degredation from low pH
    15 min
  7. 60% of drug delivery systems
    Oral CR
  8. Oral sustained and controlled release products
    • avoids frequent dosing
    • involves use of biodegradeable polymers
    • can result in toxicity if dosing regimen not followed
  9. tylenol sustained release could result in
    liver toxicity
  10. six types of oral controlled drug delivery
    • physical
    • chemical
    • osmotic
    • diffusion
    • dissolution
    • targeted
  11. Goals of oral controlled release systems
    • better control over systemic concentrations
    • sustained level of drug after a single dose
    • decrease pill burden
  12. disadvantages of OCRS
    • dose dumping can occur
    • removal of drug from systemic circulation is impossible
    • erratic or variable drug absorption
  13. Physically controled drug delivery
    altering absorption by altering viscosity of the formulation
  14. Most soluble form to least soluble form
    • solution
    • suspension
    • capsule
    • tablet
    • coated tablet
  15. particle size with fastest absorption
  16. Chemically modified drug delivery
    • prodrugs
    • salt forms
    • esters
  17. 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
  18. osmotically controlled drug delivery (L-oros)
    • drug enclosed in soft gelatin capsule
    • inner membrane
    • osmotic push layer
    • rate controlling membrane
    • delivery orifice
  19. Rate controlling membrane of L-OROS system
    • membrane controlls how much water comes in
    • ensures constant pressure for same release
  20. OROS Tri-layer
    • more for solids
    • 2 drug compartments that have different release rates
    • 1 push compartment
    • rate controlling membrane
    • overcoat
    • delivery orifice
  21. First once a day treatment for overactive bladder
    Ditropan XL
  22. dM/dt=K(A/h)(x)Cs
    • 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
  23. The rate of drug release ____ until the excess undissolved drug is depleted
    zero-order (constant)
  24. Non-zero order release sets in when
    the saturated concentration (Cs) becomes unsaturated
  25. Advantages of OROS
    • enhanced bioavailability
    • patterned release
    • reduced variability
  26. Diffusion controlled system
    drug diffuses through a matrix at a constant rate
  27. polymers for diffusion (matrix) control
    • PLGA
    • PEG
    • Polyacrylamide
    • PVA
    • xanthan and guar gums
  28. typical commercial product that utilizes matrix diffusion
    nifedipine er
  29. Encapsulated dissolution controlled system
    once coating is dissolved drug core is available for immediate release and absorption
  30. control of encapsulated dissolution time
    • thickness of polymeric membrane
    • compressing multiple particles of varying thickness of drug
  31. Examples of materials used for micro encapsulation
    • cellulose
    • shellac
    • gelatin
    • carnuba wax
  32. 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
  33. Enteric coating of tablets are designed to release drug
    in the small intestine or large intestine
  34. coating that allows for release in large intestine
    chitosan polymers