Solutions

Question 1

What are some advantages of the solution dosage form

Answer 1

• Provide homogenous doses
• Doses are easily adjusted
• Immediately available for absorption
• Can be used by any route of administration
• Can be used for patients unable to swallow

Question 2

What are some disadvantages of the solution dosage form

Answer 2

• Lower stability
• Drug may be insoluble in required solvent
• Microorganism growth - requires preservatives
• Problems with handling, transport, storage
• Requirement of additives (to mask taste)
• Less accurate dosing

Question 3

Explain the concept of solubility of gases in liquid

Answer 3

Henry’s Law:
- At constant temp, the solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid

Question 4

Differentiate between dissolution and dissolution rate

Answer 4

Dissolution: transfer of molecules from solid state to solution

Dissolution rate: How fast this process occurs

Question 5

What are the 2 stages of the dissolution process

Answer 5

1. Interfacial reaction: Transfer of solute from solid to liquid (melting)
2. Migration of solute from surface of solute through the boundary (stagnant layer) into the bulk solution (rate-limiting step)

Question 6

What are 2 ways to enhance solubility using the Noyes Whitney equation

Answer 6

1. Increase surface area by decreasing particle size
2. Reduce diffusion layer thickness (reduces drug concentration in diffusion layer) by mechanical stirring

Question 7

What is the purpose of in vitro dissolution testing

Answer 7

• to assess the quality of solid drug products
• As a prognostic tool for the performance of solid drug products in the gastrointestinal tract

(main goal is to measure the rate at which the drug releases from the dosage form to the intestine)

Question 8

What is the partition coefficient equation

Answer 8

organic phase/aqueous phase

Question 9

Can purified water be used in parenteral solutions

Answer 9

no

Question 10

What are the conditions for water for injection and what is it used for

Answer 10

-must be pyrogen free
- Does not need to be sterile
used for parenteral solutions

Question 11

What are advantages of alcohol as a solvent (2)

Answer 11

• higher solubility of many organic solutes
• increased stability (decrease in hydrolysis, decrease in bacterial growth)

Question 12

List the 7 factors affecting solubility

Answer 12

1. Temperature
2. Structure of drug
3. Solvents
4. Solubilizing agents
5. Complex formation
6. Other solutes
7. pH

Question 13

What is the delta H usually in dissolution processes? How does it affect solubility

Answer 13

usually ENDOthermic, increase in temp. results INCREASE in solubility

If exothermic, increase in temp results DECREASE in solubility

Question 14

Define salting-in and salting out

Answer 14

Salting- in: adding salt INCREASES solubility
Salting-out: adding salt DECREASES solubility

Question 15

What is the common ion effect

Answer 15

Adding salt that contains an ion the same as the electrolyte will decrease the solubility of the electrolyte

Question 16

How does complex formation increase the solubility of a compound

Answer 16

The addition of an electrolyte that reacts with a solute to form an inorganic complex ion can
increase or decrease the solubility of a compound depending upon the solubility of the complex ion that is formed.

Question 17

What is the purpose of a solubilizing agent?
Describe the 2 classes

Answer 17

Surfactants (form micelles to dissolve hydrophobic drugs)
- are amphiphilic compounds that aggregate into micelles which shield the hydrophobic groups from water contact and provide a hydrophobic phase that hydrophobic drugs can be solubilized in

Complexing agents
- Form a complex with drug to increase solubility (either through stacking interactions or inclusion complex)

Question 18

What is the MAIN difference between elixir and syrup

Answer 18

Elixir: hydroalcoholic solution
- MUST contain alcohol

Syrup: no alcohol necessary

Question 19

What are aromatic waters and spirits generally used for?

Answer 19

They are hydrolacooholics (water and alcohol) and are used as flavouring agents

Question 20

What are common things added to collodion (topical)

Answer 20

Nitrated cellulose or pyroxylin which forms the tough flexible film layer on the skin

Question 21

What are some substances contained in evacuation enemas

Answer 21

Sodium chloride
Sodium bicarbonate
Sodium phosphates

Question 22

What are the chemical types associated with Sweet, Sour, Bitter, and Salty tastes?

Answer 22

Sweet: low molecular weight compounds (sucrose, sorbitol, mannitol)

Sour: a result of a lot of H+ ions (acidity)

Bitter: occurs when an ion in a salt has a high molecular weight or the compound is a base (caffeine, codeine)

Salty: ionic compounds (NaCl, Na salicylate)

Question 23

Contrast between an antioxidant and a chelating agent

Answer 23

Antioxidant:
- disrupts the free radical chain by reacting with free radicals.
- Common: Sodium thiosulfate, sodium bisulfite (sulfur salts)

Chelating agent:
- complexes trace metal ion contaminants in solutions by eliminating their ability to cause the free radical reactions
- Common: EDTA

Question 24

What are the main classes of preservatives?

Answer 24

Alcohols: ethanol, propylene glycol
Acids: benzoic acid, sodium benzoate
Esters: Paraben - esters of p-hydroxybenzoic acid

Question 25

What are some examples of pharmaceutically acceptable buffer systems

Answer 25

Carbonates, citrates, gluconates, lactates, phosphates, tartrates

Question 26

What are the most common tonicity modifiers

Answer 26

Sodium chloride and destrose

Question 27

What type of compounds are usually viscosity modifiers?

Answer 27

polymeric compounds

Question 28

What are 5 main excipients in mouthwashes

Answer 28

alcohol
Humectants
Surfactants
Flavours
Colours

Question 29

What do nasal solutions contain

Answer 29

tonicity modifiers