Test 3-Drug stability

Question 1

USP definition of stability

Answer 1

the extent to which a product retains, within specified limits, and throughout its period of storage and use (i.e., its shelf-life), the same properties and characteristics it possessed at the time its manufacture

Question 2

Types of stability

Answer 2

• physical
• chemical
• microbiological
• therapeutic
• toxicological

Question 3

Physical stability

Answer 3

-retains original physical properties including original appearance, palatability, uniformity, dissolution, and suspendability
-chemical structure of the drug is not changing

Question 4

Physical stability issues can be the result of…

Answer 4

• polymorph conversion
• liquefaction of powders
• precipitation from solution (dilution of or change in solvent, change in pH)
• change in flow properties or viscosity
• separation of phases in coarse dispersions (caking of susp, creaming of an emulsion)

Question 5

Chemical stability

Answer 5

-occurs when the drug structure remains the same throughout shelf life
-retains chemical integrity and labeled potency

Question 6

Chemical drug degradation

Answer 6

results in a change in the drug structure through modification of functional groups

Question 7

Why do we care about chemical stability?

Answer 7

• storage conditions
• proper container
• interactions when mixing drugs and dosage forms
• stability related to route of administration

Question 8

Pathways of drug degradation

Answer 8

• hydrolysis
• oxidation
• photolysis
• racemization

Question 9

Hydrolysis

Answer 9

the breaking of a molecular bond by reaction with water

Question 10

Functional groups susceptible to hydrolysis

Answer 10

• esters and lactones
• carbamates
• amides
• imides
• lactams

Question 11

Oxidation

Answer 11

• loss of electrons
• an increase in the number of carbon-to-oxygen bonds in a molecule
• a reduction in the number of carbon-to-hydrogen bonds in a molecule

Question 12

3 steps of oxidation

Answer 12

Initiation, propagation, termination

Question 13

Initiation step

Answer 13

Formation of the free radical promoted by oxygen, light, metal cations in trace quantities

Question 14

Propagation step

Answer 14

free radical takes an electron from another drug molecule, producing another free radical

Question 15

Termination step

Answer 15

two free radicals find each other; electrons are now paired, reaction stops

Question 16

Functional groups susceptible to oxidation

Answer 16

• alkenes
• phenols
• aldehydes
• ethers on aromatic rings
• thiols and thiol ethers
• enols

Question 17

Photolysis

Answer 17

normal sunlight or room light may cause substantial degradation of drug molecules

Question 18

Many drug solutions that undergo ______ and _______ will yellow or darken in color

Answer 18

oxidation and photolysis