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PHRM 100 – PDD > PDD 04 and 05: Stability of Dosage Forms > Flashcards

PDD 04 and 05: Stability of Dosage Forms Flashcards

1
Q

What is pharmaceutical stability?

A

extent to which a product retains the same properties and characteristics that it possessed at the time of manufacture

  • product is deemed stable if it remains within its specified limits throughout its intended period of storage and use
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2
Q

What are the 3 components of pharmaceutical stability?

A
  • physical components
  • chemical components
  • microbiological components

(all components of stability are to be retained within the specified shelf life)

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3
Q

What are the physical components of pharmaceutical stability?

A

physical properties and appearance

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4
Q

Describe the physical instability of emulsions.

A
  • coalescence
  • flocculation
  • creaming
  • breaking
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5
Q

Describe the physical instability of tablets.

A
  • capping
  • chipping
  • cracking
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6
Q

Describe the physical instability of capsules.

A
  • cracking
  • tackiness
  • mottling of coatings
  • hardening or softening of shell
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7
Q

What are the chemical components of pharmaceutical stability?

A

active ingredient retains its chemical integrity and potency

  • ie. chemical instability of acetaminophen
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8
Q

What are the microbiological components of pharmaceutical stability?

A

sterility or resistance to microbiological growth

  • ie. microbiological instability of emulsions
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9
Q

What are the factors that influence pharmaceutical stability? (5)

A
  • nature of active ingredients and excipients
  • interaction between drug and excipients
  • manufacturing process – heat, moisture
  • packaging
  • storage (environment and time) and handling
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10
Q

What two characteristics define the stability of a pharmaceutical product?

A
  • specifications
  • shelf life
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11
Q

What are specifications?

A

tests → analytical methods → acceptance criteria (depending on each product)

  • ie. active ingredient content → HPLC → > 90% of labeled dose
  • ie. impurity content → HPLC → < 2% of total dose
  • ie. appearance → eye examination → clear colourless solution
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12
Q

What is shelf life?

A

time interval that a product is expected to remain within approved specifications

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13
Q

How can pharmacists help ensure product stability? (5)

A
  • observe expiration dates and rotate stock
  • store under recommended conditions
  • observe for evidence of instability
  • proper treatment of products subject to additional manipulation – repackaging, dilution or reconstitution, preparation of parenteral products
  • patient education
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14
Q

What are the 3 major types of chemical instability?

A

hydrolysis > oxidation > photolysis

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15
Q

What is hydrolysis?

A

mediated by water and could be promoted at certain pH values

  • susceptible groups include lactams, esters, and amides
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16
Q

What is oxidation?

A

often mediated through reaction with atmospheric oxygen

  • often initiated by trace amounts of impurities
  • ie. Cu ions increases vitamin C oxidation by 10,000x
  • ie. hydroperoxides in PEG-based suppositories oxidizes codeine to codeine-N-oxide
17
Q

What is photolysis?

A

absorption of light with energy sufficient to achieve activation and degradation of the molecule

  • molecules containing bonds absorb light – aromatic hydrocarbons, aldehydes, ketones
  • degradation can occur under sunlight or room light depending on the absorption spectrum
18
Q

What are the 3 stabilization methods used to protect drug products from hydrolysis, oxidation and photolysis?

A
  • pharmaceutical packages
  • storage conditions
  • drug formulation
19
Q

How can pharmaceutical packages help with stabilization to protect drug products from hydrolysis, oxidation and photolysis? (3)

A
  • blister – reduce air contact
  • orange vials – protect from light
  • absorbing pack – decrease moisture
20
Q

How can storage conditions help with stabilization to protect drug products from hydrolysis, oxidation and photolysis?

A

avoid moisture, light, and high temperature

21
Q

How can drug formulation help with stabilization to protect drug products from hydrolysis, oxidation and photolysis? (3)

A
  • antioxidants
  • chelating agents (ie. to remove metal ions that promote oxidation)
  • free radical terminators (BHA, BHT)
22
Q

What is the law of mass action?

A

rate of reaction is proportional to product of molar concentration of reactants each to the power of moles of the substance undergoing reaction

  • A + B → C + D
  • rate ∝ [A]^1 [B]^1
23
Q

What parameter are we interested in with drug degradation?

A

loss of reactant (drug A)

24
Q

What is the order of reaction

A

sum of powers to which the reactant concentrations are raised in the rate expression (for simple single step reactions)

25
Q

What is a zero order reaction (pseudo zero order reaction)?

A

one of the most common orders of reaction in drug stability

  • units for k0: concentration/time
  • rate of reaction is independent of reactant concentration – therefore rate equation does not contain a concentration term
26
Q

What is a first order reaction (pseudo first order reaction)?

A

one of the most common orders of reaction in drug stability

  • units for k: 1/time
27
Q

What is a second order reaction?

A

sum of powers = 2

28
Q

Where do pseudo (or apparent) zero order reactions occur?

A

in suspensions

  • because there is excess drug in solid form, which can replace the drug in solution that degrades, drug concentration in solution is constant (until all solid is gone)
29
Q

What order is a general drug degradation reaction where A is a drug in solution?

A

first order

30
Q

What is half-life (t1/2)?

A

time required for drug concentration to become half (50%) of original concentration

31
Q

What is shelf life?

A

time to reach a certain percent of the labelled claim – typically 90-95%

  • for pharmaceuticals, acceptable shelf life is never < 90% of original value
32
Q

Why is the stability of a suspension better than a solution for a given drug?

A

as temperature increases, number of molecules with sufficient energy to react increases

  • Arrhenius demonstrated that reaction rate constant has an exponential dependence on temperature
33
Q

Arrhenius Equation

A
  • k: rate constant
  • Ea: activation energy (cal/mol or J/mol)
  • T: absolute temperature (K)
  • R: gas constant (J/mol/K or other units)
  • A: frequency factor (related to number of collisions)
34
Q

What is the accelerated stability study?

A
  • designed to increase rate of chemical degradation or physical change of a drug substance or product by using exaggerated storage conditions
  • used to support tentative expiration dates in the event that full shelf-life studies are not available

PHRM 100 – PDD (14 decks)

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