exam 2 munson

Question 1

controlled drug delivery

Answer 1

temporal: sustained (delayed + extended) and pulsatile release
spatial: systemic, local, targeted (avoids sides)

Question 2

controlled release advantages

Answer 2

maintains optimum drug concentrations (controls drug release)
improve efficiency with less drug –> targeted
minimize sides
less frequent admin
increase patient convenience + compliance w/ dose regimen

Question 3

controlled release disadvantages

Answer 3

higher production costs
leakage of drug mass
difficult to stop drug release
Biocompatibility with body’s immune system
surgical operation

Question 4

temporal control of drug delivery

Answer 4

maintains drug in therapeutic window
needed:
- optimizes drug concentration-time profiles
- reduces admin frequency
- stimulates multiple dosing via combination of immediate release dosage
not needed:
- drugs with long half-life
- drugs of which long-term effect is undesirable
- drugs which require immediate effect

Question 5

drug release control mechanisms

Answer 5

diffusion-controlled systems: reservoir + matrix devices
dissolution
erosion
osmotic - can be controlled release
swelling

Question 6

diffusion-controlled systems

Answer 6

drug diffuses through polymer network is rate-limiting step
reservoir system
drug + matrix former system

Question 7

reservoir system

Answer 7

release rate through membrane. drug must pass through matrix –> drug release is constant (zero-order)

Question 8

drug + matrix former system

Answer 8

drug closest to surface diffuses first.
lot of drug is initially release then decreases over time (SA decreases over time)
drug release depends on device geometry

Question 9

ocusert

Answer 9

pilocarpine reservoir
rate controlling membranes –> constant rate of release with respect to time

Question 10

tetracycline periodontal fibers

Answer 10

cylinder membrane that drug will diffuse through
control amount of drug release by length
membrane allows for constant diffusion

Question 11

norplant

Answer 11

non-erodible subdermal implant contraceptive
release constant amount of drug per day
sides: disturbance to menstrual cycle, pain, scarring

Question 12

drug release equation

Answer 12

M = (DSKCsT) / h
M: amount of drug flowing through membrane
D: diffusion coefficient
S: cross section area (cm2)
K: partition coefficient of the membrane –> how much drug wants to be in membrane K >1 wants to be in membrane
Cs: drug concentration in reservoir
T: time
h: thickness of membrane

Question 13

patches

Answer 13

backing: covers nicotine and prevents evaporation
reservoir: stores therapeutic nicotine that prevents urge to smoke
rate controlling membrane: provides steady stream of therapeutic nicotine to prevent cravings
adhesive and release liner: contains loading bolus

Question 14

diffusion matrix equation

Answer 14

M = k * t^1/2

Question 15

dissolution systems

Answer 15

encapsulated polymer membrane:
- membrane slowly dissolves –> releases drug
Matrix:
- matrix dissolves and allows release of drug
- matrix shrinks over time

Question 16

dissolution matrix

Answer 16

M = DSΔCt / h
S changes with dissolution of drug+polymer matrix

Question 17

osmotic systems

Answer 17

one chamber: water permeates membrane and drug is released through single orifice
two chamber: water is like plunger and pushes drug through orifice by use of membrane
film coating: permeable to water, not permeable for drug or excipients. rigid: resists the hydrostatic pressure –> push out drug
cannot chew, insensitive to pH

Question 18

erosion controlled systems

Answer 18

initial release: phase is controlled by diffusion of drug on surface or have access to surface via pores in microsphere matrix
sustained release: phase is determined by erosion of polymer –> as it erodes, trapped drug molecules are released

Question 19

two types of errosion

Answer 19

surface erosion: drug molecule system gets smaller
bulk erosion: drug diffuses out, so size of system does not change

Question 20

gliadel wafer

Answer 20

for glioblastoma (brain tumor)
place a wafer in brain to prevent reopening up
no need to remove polymer remnants
temporal control: BCNU is released in a time-controlled manner
spatial control: BCNU is released in direct vicinity of site of action

Question 21

polyanhydrides

Question 22

lupron depot

Answer 22

poly (lactic-co-glycolic acid)
prostate cancer
injected i.m. through 22G
1-4 month release for advanced prostate cancer

Question 23

PLGA

Answer 23

PLGA (glycolic acid + lactic acid) –> (hydrolysis) –> renal excretion –> TCA cycle –> CO2 + water

Question 24

swelling controlled systems