Suspensions

Question 1

What are the 3 things we can classify solutions based off of?

Answer 1

The nature of the particle
Route of administration
Solvent/dispersion medium

Question 2

What is Henry’s Law?

Answer 2

States that at a constant temperature, the solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid. Describes solubility of gases in liquids.

Question 3

What are the two stages of the dissolution process?

Answer 3

Transfer of solute from the solid to the liquid state.
Migration of solute from the surface of the solute through the stagnant layer into the bulk solution. Usually the rate limiting step.

Question 4

What is the Noyes-Whitney equation? Define sink conditions.

Answer 4

Describes the dissolution of spherical particles.
Sink conditions: molecules diffuse in the direction of lower concentration. Diffusion is maximum when concentration gradient is the highest.

Question 5

What is the USP convention for the expression of solubility?

Answer 5

USP uses the volume of solvent needed to dissolve 1g of solute to express solubility

Question 6

Define partition coefficient. Explain what values of logP mean

Answer 6

Partition coefficient and logP are a measure of lipophilicity.
LogP>0, drug is lipid soluble
LogP<0, drug is water soluble
LogP=0, drug is equally soluble in water and octanol
Optimal value is 3. If too high, drug is too insoluble in water to effectively partition out of the membrane. If too low, drug is too soluble in water to partition into the membrame.

Question 7

What is the minimum acceptable grade of water used for pharmaceutical preparations?

Answer 7

Purified water

Question 8

What are the different types of pharmaceutical waters? (4)

Answer 8

Purified water: for non-parenteral solutions
Water for injection: pyrogen-free water
Sterilized water for injection: cannot contain any additional substances or preservatives. Heat sterilized water for injection.
Pyrogen free: free from pyrogens

Question 9

What are the 4 common types of alcohol USP?

Answer 9

Alcohol USP: 95% ethanol
Denatured alcohol: unfit for internal use due to additives
Dehydrated alcohol: sane as absolute ethanol and is water-free
Diluted alcohol: prepared from equal volumes water and alcohol

Question 10

Define dielectric constant

Answer 10

Dielectric constant is a measure of a solvent’s polarity. The higher the constant, the more polar it is.

Question 11

Define salting-in, salting-out and the common ion effect

Answer 11

Salting in: solubility increases with added salt
Salting out: solubility decreases with added salt
Common ion effect: a decrease in solubility due to a shift in equilibrium

Question 12

How does complex formation increase solubility?

Answer 12

Complexing agents form non-covalent associations with drug molecules, increasing solubility,
Stacking interactions and inclusion complexes.

Question 13

What are the two types of solubilizing agents?

Answer 13

Surfactants– forms micelles at CMC

Complexing agents

Question 14

What is the effect is an increase in pH on the solubility of a weak acid and a weak base?

Answer 14

Weak acid: increasing pH leads to a decrease in proton concentration, increasing solubility
Weak base: increasing pH leads to a decrease in proton concentration, decreasing solubility

Question 15

Define endothermic vs exothermic dissolution process

Answer 15

Endothermic: heat is absorbed, increase in solubility
Exothermic: heat released, decrease in solubility

Question 16

What is the difference between syrups and elixirs?

Answer 16

Syrups: viscous, aqueous solutions that may or may not contain less than 10% alcohol
Elixirs: hydroalcoholic solutions.

Question 17

Why should you be careful using heat when preparing syrups?

Answer 17

Heat can cause hydrolysis of sucrose into monosaccharides.

Question 18

What are the 3 uses of topical solutions?

Answer 18

Antiseptic, astringent, moisturizer

Question 19

What are collodions? What can we add to them to increase flexibility?

Answer 19

Collodions: solutions designed for application to the skin in small quantities. Leave a film on the skin that contains the drug
Vegetable oils can be added to make them more flexible.

Question 20

What are the primary tastes and their correlated chemicals?

Answer 20

Sweet: low molecular weight polyhydroxyl compounds
Sour: result of H+ ions
Bitter: when one ion in a salt is a high molecular weight compound
Salty: ionic compounds

Question 21

What is the difference between natural and artificial sweeteners?

Answer 21

Natural sweeteners: nutritive (caloric)

Artificial sweeteners: non-nutritive

Question 22

What level of certification should an artificial colour have before being used? What concentrations are used?

Answer 22

Artificial colours can only be used in oral dosage forms.
Must be food, drug and cosmetic classification
0.0005-0.001 concentration

Question 23

How do antioxidants work? What is a chelating agent?

Answer 23

Antioxidants stabilize a compound by disrupting a chain reaction by consuming free radicals.
Chelating agents complex metal ions and eliminates their catalytic activity

Question 24

What are the three main classes of preservatives?

Answer 24

Alcohols and glycols
Acids
Esters