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Pharmaceutics > Drug Stability > Flashcards

Drug Stability Flashcards

1
Q

What are the 3 types of Degradation?

A
  1. Chemical
  2. Physical
  3. Microbiological
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2
Q

What is chemical degradation?

A

=> inaccuracy in dosing & possibly therapeutic failure

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3
Q

What is physical degradation?

A

=> decrease bioavail. => decrease therapeutic efficacy
- can occur through physiochemical changes &/or excipients such as PRODUCTION OF POLYMORPHS

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4
Q

What is microbiological degradation?

A

microbial growth & ability of the product to remain sterile/resistant to growth

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5
Q

What are the 4 types of Chemical degradation?

A
  1. Hydrolysis - decomp. of drug through rxn w/ water/solvent; as it acts as a nuc & attacks electrophilic sites
  2. Oxidation - strongly influenced by light, metal ions, O2 & oxidizing agents
  3. Photolysis - sunlight &/or room light may cause degradation through an oxidative process w/ light providing energy (a photon) for the initiation & propagation steps
  4. Miscellaneous - chemical rxns such as: hydration, additions, decarboxylation & Schiff’s base formulation can occur
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6
Q

Many compounds are more resistant to ox @ _____ pH

A

LOWER

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7
Q

Greater the # of C to O bonds, the ____ oxidized the molecule

A

MORE

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8
Q

When electromagnetic radiation absorbed by a molecule, 1 of the following events may occur:

A
  1. molecule decomposes w/ release of free radical
  2. energy retained until it can be used chemically or transferred to another molecule
  3. energy converted to heat & NO rxn occurs
  4. absorbing molecules emit light of diff wavelengths & NO rxn occurs
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9
Q

What are the 4 types of Physical degradation?

A
  1. Polymorphism - differ in internal crystal structure & therefore crystal energies differ which results in solubility differences
  2. Vapourization - ~ drugs have HIGH VP that ~ of the active is lost through vapourization
  3. Aging - where changes occur in the disintegration/dissolution properties
  4. Adsorption - drug loss to packaged materials
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10
Q

Shelf-life (t90):

A

time @ which the initial [ ] of active in the product has DECREASED by 10%

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11
Q

Half-life (t50):

A

time @ which the initial [ ] has DECREASED by 50%

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12
Q

Order of a rxn determines the _____ of [ ]-time profile; Rate constant determines its _____

A

SHAPE

SLOPE

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13
Q

Rate of rxn is proportional to ______________

A

number of collisions

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14
Q

Number of collisions is proportional to the ____________

A

product of the [ ] of the reacting species

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15
Q

What does 1st order mean?

A

drug loss is DIRECTLY proportional to the [ ] remaining w/ respect to time

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16
Q

What does 0 order mean?

A

the loss of drug is INdependent of [ ] & constant w/ respect to time

17
Q

What are the factors affecting rxn rates?

A
  1. Temp
  2. Catalysis
  3. pH
  4. Solvent effects
  5. Solubility effects
    a. hydrolysis
    b. oxidation
18
Q

What are the solvent effects generally?

A
  • INCREASE in solvent polarity accelerates the rates where CHARGE develops in the activated complex
  • DECREASES the rates where there is LESS charge in the activated complex compared to the starting material
  • Change in solvent polarity will have little or no effect on the rates where there is little difference in charge b/t the reactants & the activated complex
19
Q

What is a solubility effect?

A

drug in solution may undergo apparent 1st order rxn, but when formulated as a suspension, it decomposes through apparent 0-order kinetics

20
Q

Solubility effects: Hydrolysis

A

1) Exclude water from product
- drug must be in solution for hydrolysis to occur, so exclusion of water will slow the rate of decomposition

2) Control pH

3) Control temp
- storing @ reduced temp may INCREASE product stability, but freezing should NOT be used

4) Use of cosolvents

5) Complex formation

6) Supply drug in solid form
- form. as a suspension may be useful since drug will probs degrade through apparent 0-order kinetics

21
Q

Solubility effects: Oxidation

A

1) Protect from light

2) Exclusion of O2

3) Control of pH

4) Addition of antioxidants (are more easily oxidized than the product)

22
Q

What is real time stability testing?

A

to provide evidence on how the quality of a product, in its marketing packaging, varies w/ time under the influence of factors, such as temp, humidity & light

23
Q

What is the Q10 method of shelf-life estimation?

A

est. temp effects on rxn rates

Q10 is factor by which the rate constant INCREASES for a 10 degree C temp. INCREASE

Reasonable estimates can often be made using the value of 3

Pharmaceutics (4 decks)

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