Exam 1 - solutions

Question 1

List the types of liquid dosage forms

Answer 1

solution
emulsion
suspension

Question 2

Define “solution”

Answer 2

homogeneous molecular dispersion

Question 3

Define “emulsion”

Answer 3

liquid drops suspending
(oil in water or water in oil)

Question 4

Define “suspension”

Answer 4

solid in water or oil

Question 5

What type of liquid dosage form is milk?

Answer 5

an emulsion AND suspension

Question 6

List common solvents in solutions

Answer 6

waters or oils

Question 7

List common co-solvents in solutions

Answer 7

ethanol
glycerin
propylene glycol

Question 8

List common flavors / sweeteners in solutions

Answer 8

Sucrose
Sorbitol

Question 9

List the advantages of solutions

Answer 9

• Homogenous: no problems of content uniformity
• Easy to manufacture
• Good bioavailability (already dissolved)

Question 10

Define “buffer”

Answer 10

a solution of a weak acid and a salt of its conjugate base

Question 11

What is the role of a weak acid in a buffer?

Answer 11

removes added base (OH-)

Question 12

What is the role of the salt in a buffer?

Answer 12

removes added acid (H+)

Question 13

Henderson-Hasselbach equation

Answer 13

pH = pKa + log[A-]/[HA]

Question 14

Define “buffering capacity’

Answer 14

ability of a buffer to resist change in pH due to added OH- or H+

Question 15

What equation is used to calculate the buffering capacity of a given buffer?

Answer 15

Van Slyke equation

Question 16

Van Slyke equation

Answer 16

B = 2.3C (Ka*[H3O+) / (Ka+[H3O+]^2

Question 17

Equation for Ka

Answer 17

Ka = 10^ -pKa

Question 18

Equation for H3O+

Answer 18

[H3O+] = 10^ -pH

Question 19

Explain why a weak acid with a pKa close to the desired pH selected

Answer 19

• Provides maximum stability for drug, it is able to maintain an optimal pH for the drug so it’s not broken down instantly
• Minimize irritation with parental, ophthalmic, or nasal dosage forms by adjusting pH to be the same as the pH of body fluid

Question 20

Explain what needs to be done to minimize irritation if the pH of solution cannot match the pH of body fluid

Answer 20

• Minimize buffering capacity
• Minimize volume
• Administer slowly

Question 21

Describe the purpose of antimicrobial preservatives

Answer 21

Preservatives adsorb to the bacterial membrane and disrupt the membrane. The membrane is lipophilic and has a net negative surface charge.

It helps to protect patients against pathogens and to maintain both the potency and stability of dosage forms

Question 22

List antimicrobial preservatives that adsorb due to lipid solubility

Answer 22

Alcohols
Esters
Acids

Question 23

List antimicrobial preservatives that adsorb due to electrostatic attraction

Answer 23

Quaternary ammonium compounds

Question 24

List alcohol excipients that act as preservatives

Answer 24

Ethanol
Benzyl Alcohol
Chlorobutanol

Question 25

Describe the function of ethanol as an excipient in solution dosage forms (preservatives)

Answer 25

- requires >15% - limited to oral products - may be lost due to the volatility

Question 26

Describe the function of benzyl alcohol as an excipient in solution dosage forms (preservatives)

Answer 26

- local anesthetic action - not used orally due to the burning taste - water soluble - stable within a large pH range - commonly used in parenterals

Question 27

Describe the function of chlorobutanol as an excipient in solution dosage forms (preservatives)

Answer 27

- not used orally due to the camphor-like odor - used in parenteral and ophthalmic - volatile

Question 28

Describe the function of acids as excipients in solution dosage forms (preservatives)

Answer 28

- Only active in unionized form - Benzoic acid (pKa = 4.2 → used for oral products) - Sorbic acid (pKa = 4.8 → used for oral products and good for molds and yeast)

Question 29

Describe the function of parabens (esters of p-hydroxybenzoic acid) as excipients in solution dosage forms (preservatives)

Answer 29

Preservative acting by lipophilic adsorption

Question 30

List lipophilic parabens used as excipients in solution dosage forms (preservatives)

Answer 30

propylparaben, butyl paraben **best against mold and yeast**

Question 31

List less lipophilic parabens used as excipients in solution dosage forms (preservatives)

Answer 31

methyl paraben, ethyl paraben **best against bacteria**

Question 32

List common quaternary ammonium compounds used as excipients in solution dosage forms (preservatives)

Answer 32

Benzalkonium chloride (Zephirin) **electrostatic adsorption** Cetyltrimethylammonium chloride (Cepryn)

Question 33

Explain the need for antioxidants in drugs based on their state of matter

Answer 33

drug substances are less stable in aqueous media compared to solid

Question 34

What is the main degradation pathway for antioxidants?

Answer 34

oxidation

Question 35

Describe the pathway of degradation for antioxidants

Answer 35

initiated via heat, light, peroxides, metals then causes free radicals causing it to react with oxygen producing MORE free radicals

Question 36

Give examples of antioxidant agents

Answer 36

Free radical scavengers Reducing agents Chelating agents

Question 37

Describe "free radical scavengers"

Answer 37

delayed oxidation by reacting with free radicals

Question 38

Give examples of free radical scavengers

Answer 38

BHA BHT

Question 39

Describe "chelating agents"

Answer 39

antioxidant synergists / little antioxidant effect

Question 40

Describe "reducing agents"

Answer 40

lowing redox potentials than drug // more readily oxidized

Question 41

Give examples of "chelating agents"

Answer 41

Citric acid EDTA

Question 42

Give examples of "reducing agents"

Answer 42

Sodium bisulfite Ascorbic acid Thiols