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Oral Dosage Forms— Modified Release > PS400 exam 4 > Flashcards

PS400 exam 4 Flashcards

(46 cards)

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1
Q

how does mass transfer occur?

A

via diffusion or convection

dispersion (diffusion + convection)

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2
Q

what is convection and diffusion?

A

diffusion : Brownian motion & movement towards equilibrium
convection: mass flow of liquid

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3
Q

what is mass transfer important for?

A

dissolution
crystallization
membrane transport
movement within dosage forms
pharmacokinetics

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4
Q

what is the equation for mass transfer?

A

t= L^2/ 6D

t- time
L distance
D-diffusion coeff

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5
Q

what does diffusion time depend on?

A

viscosity of solvent

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6
Q

what t do gasses and solids have?

A

gasses have lower t
solids have higher t

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7
Q

how does viscosity influence the diffusion coefficient and diffusion time?

A

increased viscosity–>
decreased diffusion coefficient–> increased diffusion time

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8
Q

what is flux? recognize equation

A

net rate of a drug movement in a specific direction per area?

j= 1/A dm/dt (dissolution rate)

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9
Q

in flux, what is the relationship between j and A?
what is the relationship between j & dm/dt and A & dm/dt ?

A

j and A are inversely proportional

j and dm/dt–> directly
A and dm/dt–> directly

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10
Q

what is ficks 2nd law of diffusion under steady state conditions?

A

C= mx +b
j= constant

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11
Q

what is ficks 1 law of diffusion equation?

A

j= -D dC/dx ( change in concentration)

j and dc/dx have opposite signs

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12
Q

for ficks 2nd law of diffusion, concentration is linear with position until? what is it independent of?

A

untill the outside concentration is reached
independent of time

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13
Q

what is drug concentration at tablet surface equal to at steady state?

A

drug solubility in the dissolution medium

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14
Q

what is drug concentration at L equal to?

A

drug concentration in bulk solution , which is equal to 0 for sink conditions

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15
Q

what is the noyes Whitney equation for dissolution rate?

A

dm/dt=DA (Cs-CL/L)

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16
Q

how does particle size affect dissolution rate?

A

decrease size–> increase A
so increase dm/dt

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17
Q

how does mixing of dissolution medium affect dissolution rate?

A

increasing in mixing–> decreases L
increases dm/dt

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18
Q

how does viscosity of dissolution medium affect dissolution rate?

A

decrease viscosity –> increase D
increase dm/dt

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19
Q

how does increasing volume of dissolution medium affect dissolution rate?

Study These Flashcards
A

increase V–> decrease Cl
increase dm/dt

20
Q

what is chemical kinetics and how do we apply it to pharmacy?

Study These Flashcards
A

study of rate of chemical reactions

helps optimize stability & predicting shelf life based on degradation rate

21
Q

what are zero order kinetic equations?

Study These Flashcards
A

rate law: A0- At=kt
and t1/2=A/2ko

22
Q

what are first order kinetic equations?

Study These Flashcards
A

ln At/ A0= -kt and t1/2=0.693/k1

23
Q

what order do suspensions follow?

24
Q

concentration of a solution remains constance because….

Study These Flashcards
A

solid can go into solution to replace reacted drug

25
what are elementary reactions?
have single transition/ activation state
26
what are bimolecular reactions?
2 molecules reacting, most common
27
what is transition theory used for?
to determine the energy required for reactants to reach the transition state
28
what are the assumptions of transition state theory?
fast equilibrium between reactants and transitions state species reaction rate is proportional to the concentration of the transition state species
29
what is ionic strength?
measure of concentrations of ions in a solution more ions---> higher ionic strength
30
whether the rate constant of increases or decreases depends on the product of charges..... what happens when: ++ or -- + 0 or - 0 -+ or +-
increase ionic strength and K increase ionic stength reversible with K increase ionic strength and decrease K
31
what happens when ionic strength is low and high?
low: ions have large ionic atmospheres high: ions in solution shield the ions or interest and the ion atmosphere reduces in size
32
effect of ionic strength on reaction rate at high ionic strength?
like charges don't repeal easily--> favoring products (small ions atmosphere ar shield from seeing each other) opposing charges attract each other less, favoring reactants
33
effect of ionic strength of reaction rate at low ionic strength?
like charges more easily repel each other, favoring reactants (large ion atmosphere see each other at greater distance) opposing charges more essaying attract each other, favoring products
34
what is dielectric constant?
measure of attraction/ repulsion between ions in a solution
35
what happens to dielectric constant (e) when: ++ or -- +/- 0 -+
increase e and k or decrease when adding alcohol no k effect, decrease e increase e and dec k or decrease e and inc k (add alcohol)
36
what is the Arrhenius equation?
lnk=ln A- Ea/RT
37
for a 10c reduction in temp, what happens at Ea=10k, 20k and 30k?
shelf life increases by: 2x, 3x, 6x
38
for 20c reduction in temperature, shelf life increases at Ea=10k, 20k, 30k by:
4x, 9x, 36x
39
what is accelerated stability studies?
determine shelf life done by measure stability at higher temps and predicting stability at storage temp thru extrapolation
40
for accelerated stability studies, what do we measure at each temperature?
rate constant over a range of buffer concentrations, extrapolate to determine rate with no buffer
41
what is step 1 and 2 of accelerated stability studies?
determine bufferless k at several temps at specified ph plot ln kobs vs 1/T and extrapolate to desired shelf life temp to obtain K extrap
42
Ph profile, what happens at low, high and int ph?
low: H catalyzes reaction (acid catalysis) high: OH catalyzes intermediate: buffering species catalyze reaction
43
what is passive targeting?
the natural physiological and anatomical characteristics of the body to accumulate drugs in specific areas, particularly in tumors or inflamed tissue relays on EPR effect
44
what is active targeting?
uses specific molecular interactions to direct drugs to particular cells or tissues examples is HER2 targets
45
Doxil manufacturing?
lipids dissolve in ethanol mix with aq solution MLV formation high pressure extrusion SUV. formation DOX loading purification/ sterilize Doxil
46
what is liposome manufacturinhg?
mix w aq solution MLV format high pressure exterustoin

Oral Dosage Forms— Modified Release (5 decks)

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