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Pharmaceutics - Test 3 > Rxn Rates, Partitioning, Assays (Classes 13-15) > Flashcards

Rxn Rates, Partitioning, Assays (Classes 13-15) Flashcards

1
Q

What is temperatures effect on reaction rate?

A

increased temp = increased rxn rate

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2
Q

What are 4 ways to affect reaction rate besides temperature?

A

Light, moisture, pH, catalysts

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3
Q

For every 10 degree increase in temperature, how much do you expect the reaction rate will increase?

A

2-3 fold increase for every 10 degree increase

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4
Q

For the arrhenius equation, what value gives you the slope?

A

“-Ea/R”

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5
Q

What is the purpose of using the arrhenius equation?

A

To calculate reaction rate and activation energy

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6
Q

What is k in the arrhenius equation and what are its units?

A

rate constant; 1/conc*time

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7
Q

What is A in the arrhenius equation and what does it represent?

A

A = Arrhenius Factor; Represents collision frequency

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8
Q

What are the units for A in the arrhenius equation?

A

1/sec or s^-1

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9
Q

What is the arrhenius equation?

A

ln(k) = lnA - Ea/RT

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10
Q

In an arrhenius plot, what is used in the y and x axes?

A

ln(k) vs. 1/T

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11
Q

What R value do you use in the Arrhenius equation and what are its units?

A

8.314 J/mol*K

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12
Q

If you are given k values and temperature values, how do you calculate Ea (Activation energy)?

A

Calculate ln of k and 1/T values; Calculate slope then calculate Ea from Slope = -Ea/R

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13
Q

How do you calculate the arrhenius factor once you have activation energy?

A

Plug in slope & 1/T values into Arrhenius equation [ln(k) = lnA - Ea/R * 1/T] and solve for A

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14
Q

What are the advantages of accelerated stability testing?

A

quick detection of drug degradation, prediction of shelf-life/half-life, rapid quality control

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15
Q

What are 2 reasons to do accelerated stability testing rather than testing in real time?

A

More efficient, More economical

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16
Q

What is the effect of increased temperature on the rate of drug degradation?

A

More temp, More degradation

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17
Q

Which analytical detection method utilizes adsorption in the assessment process?

A

HPLC

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18
Q

What do detection methods not tell you?

A

Structure of the drug; They tell you quantity present & degradation products present

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19
Q

For what reasons would you use UV-Vis spectroscopy?

A

determination of pKa/partition coefficient, determine rxn kinetics, determine drug release

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20
Q

What detection methods prefer a chromophore to be present on the molecule for detection?

A

UV-Vis & HPLC

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21
Q

What is the wavelength range for using UV-Vis?

A

200-700nm

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22
Q

What are some advantages to using UV-Vis?

A

Easy to use, inexpensive, good precision, automated, determines some properties

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23
Q

What are some disadvantages to using UV-Vis?

A

Not useful for mixtures, Must have chromophore, moderately selective

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24
Q

How does HPLC work?

A

A pump passes a pressurized liquid solvent containing the sample through a column with adsorbent material. Each component interacts differently with the adsorbent material causing variable flow rates/variable separation of the components as they pass out of the column

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25
Q

What is the active component of a column in HPLC called?

A

Sorbent

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26
Q

What is the significance of “HP” in the HPLC detection method?

A

HP stands for High Performance (or Pressure). The pressure is 50-250 bar in HPLC, whereas normal liquid chromatography uses gravity

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27
Q

What’s the main reason to use HPLC?

A

To separate and analyze the components of a mixture

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28
Q

Besides separating and analyzing mixtures, what are some other uses of HPLC?

A

Monitor drug stability, measure partition coefficient, and drug-protein binding

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29
Q

In straight-phase HPLC, is a polar or nonpolar substance used for the mobile phase?

A

Non-polar mobile phase, Polar stationary phase

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30
Q

In straight-phase HPLC, will hydrophilic or hydrophobic compounds be eluted first?

A

Hyrophobic compounds

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31
Q

In straight-phase HPLC, would you add a hydrophilic or lipophilic solvent to slow down elution?

A

Lipophilic solvent

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32
Q

In reverse-phase HPLC, is a polar or nonpolar substance used for the mobile phase?

A

Polar (Hydrophilic) Mobile Phase, Non-polar (Hydrophobic) stationary phase

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33
Q

Why is reverse-phase used over straight-phase?

A

Because adjustments can be made most easily and inexpensively in reverse-phase HPLC

34
Q

In reverse-phase HPLC, will a polar solvent elute more quickly or more slowly than a non-polar compound?

A

More Quickly. Since RP-HPLC uses a polar sorbent, polar solvents elute more quickly

35
Q

What are the strengths of HPLC?

A

Easily controlled, precise, selectivity can be adjusted, automated

36
Q

What are some weaknesses of using HPLC?

A

Expensive, Drugs must be extracted prior to use, large amounts of waste

37
Q

How does mass spectrometry work?

A

Uses electron bombardment to ionize fragments and then measure molecular weight of the fragments

38
Q

On a mass spectrometry report, what will the x and y axis represent?

A

y-axis: percent abundance; x-axis: mass/charge ratio

39
Q

What do the small spikes in a mass spec report represent?

A

molecule fragments or impurities

40
Q

What are the main advantages of using mass spec?

A

Protein analysis, Coupling to chromatagraphic instruments, & rapid ID of molecule/impurities

41
Q

What are some disadvantages of Mass spec?

A

Expensive, Not routinely used in QC, Requires trained personnel/maintenance

42
Q

What are 2 types of mass spec that are used for protein analysis?

A

electrospray MS & time-of-flight MS

43
Q

What would an anesthesiologist use mass spec for?

A

determine respiratory quotient (CO2 eliminated/O2 consumed)

44
Q

How many diastereomers are there in penicillin, given that there are 3 chiral carbons?

A

8 diastereomers; Using 2^n with n being the number of diastereomers, 2^3 = 8

45
Q

What 2 things can photodegradation do to a drug?

A

cause the drug to be inactive or cause it to be harmful

46
Q

What 3 things can you do to prevent photodegradation in a drug?

A

Store away from light, add an antioxidant, Use an additive that will absorb light

47
Q

What regions of drugs are responsible for light absorption?

A

double bonds; benzyl rings

48
Q

What clinical advice would you give to a patient taking photo-sensitive drugs?

A

Use drugs at night, store drug away from light, Use sunscreen or avoid sun, Do not take with other drugs that also cause sun sensitivity

49
Q

What is the definition of diffusion?

A

random movement of particles from high concentration to low concentration; often across a membrane

50
Q

What are three types of membranes for diffusion?

A

monolithic, porous, fibrous

51
Q

What is the difference between Fick’s first and second laws?

A

First law is used under steady state conditions; Second law is used under variable conditions

52
Q

For what reason would you use Fick’s First law?

A

To determine flux (diffusion rate) under steady state conditions

53
Q

What must be true in order for Fick’s first law to apply?

A

Steady state conditions & constant rate of diffusion

54
Q

What is the formula for Fick’s first law?

A

J = -D(dC/dx)

55
Q

How will the thickness of a membrane affect flux?

A

Thicker membrane = slower flux

56
Q

Which is more thermodynamically favorable, positive or negative flux?

A

positive;

57
Q

What value should be negative to generate a positive flux?

A

dC (Change in concentration); This means that flux is going from high concentration to low concentration

58
Q

What are the units for flux, J?

A

mol/cm^2s or g/cm^2s

59
Q

For what reason would you use Fick’s Second law?

A

To determine flux (diffusion rate) under non-steady state conditions

60
Q

What is the stokes-einstein equation used for?

A

To determine the diffusion coefficient

61
Q

Increasing particle radius has what effect on magnitude of flux?

A

decreases

62
Q

Increasing viscosity has what effect on magnitude of flux?

A

decreases

63
Q

What is the diffusion coefficient primarily dependent on?

A

Particle radius

64
Q

What factors affect the diffusion coefficient?

A

Temperature, Viscosity, and particle radius

65
Q

What are the units of the diffusion coefficient, D?

A

cm^2/sec

66
Q

What is partitioning?

A

Deposition of a drug between 2 phases based on affinity of drug for 1 layer vs another

67
Q

What is the partition coefficient?

A

Ratio of concentration of drug in oil layer vs water layer ([Co]/[Cw])

68
Q

If drug is more lipophilic, will that make the PC go higher or lower?

A

higher

69
Q

What is the difference between intrinsic and apparent partition coefficients?

A

Apparent coefficient looks at sum of all species (ionized & unionized) in aqueous phase (denominator); Intrinsic only looks at concentration of drug in aqueous phase

70
Q

Does log P represent the log of PCo or PC’?

A

PCo

71
Q

Which partition coefficient measurement would you use for in vivo assessments?

A

Apparent PC (need to assess drug at various pHs)

72
Q

As pH increases, what happens to the apparent partition coefficient?

A

decreases for base, increases for acid

73
Q

At a pH lower than pKa, would the PC’ of a weak base be higher or lower than its 1/2 Pco?

A

lower (in weak bases, increased H+ ionizes the base causing more drug particles to increase in aqueous phase -> increases denominator -> decreases total number)

74
Q

To calculate pKA, how would you use the partition coefficient?

A

Pco/2 = point to determine pKa

75
Q

Is partitioning an appropriate method with surfactants?

A

No. Surfactants will tend to reside at the oil/water interface & may form micelles

76
Q

What does the pH-partition hypothesis state?

A

Absorption of drugs dependent upon fraction of non-dissociated drug at intestinal pH

77
Q

How is drug absorption related to the partition coefficient?

A

Higher PC = higher absorption

78
Q

How do antacids affect the partition coefficient in relation to an acidic drug?

A

Antacids raise pH -> increases drug ionization -> decreases PC -> decreases acidic drug absorption

79
Q

What are the benefits of developing prodrugs?

A

change solubility, permeability, stability

80
Q

What is one way you could create a prodrug?

A

Convert a carboxylic acid functional group to an ester

81
Q

Differentiate between log P and log D values?

A

A log P value is the log of the intrinsic partition coefficient, whereas a log D is the log of the apparent partition coefficient

Pharmaceutics - Test 3 (3 decks)

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