PDD: L4/5 Dispersions I & II

In a suspension, the dispersing phase is …-based and the dispersed phase is …

water, solid drug particles

Emulsion is … in … and vice versa

oil, water

In an emulsion, the dispersing phase is …-based and the dispersed phase is …- based

water, liquid oil

Suspension and emulsions belong to … dispersions

coarse

Gels belong to … dispersions

fine

What are the particle size for the dispersed phase in suspensions and emulsions (coarse dispersions)?

10-50 micrometers

What are the particles size for the dispersed phase in gels (fine dispersions)

0.5-10 micrometers 

Emulsions usually appear … or …

milky, cloudy

Dispersions needs to be … for accurate dosing

homogenous

Suspension preparations contain … divided drug particles are distributed … in a vehicle in which the drug exhibit … solubility 

finely, uniformly, low

What is an advantage of the dry powder form?

Longer shelf life

Advantages of suspensions:

• Increased … compared to solutions

• Ease of … compared to solid dosage forms

• … in administration of a range of doses

• Improved … compared to solutions

stability, swallowing, Flexibility, palatability

Drug degradation happens when it comes into contact with …

water

Stability is the … of the particles in a suspension

sedimentation

Stoke’s law: dx/dt = D²(p_i - p_e)g/18η

Dx/dt = rate of …

D = … of particles

ρ_i and ρ_e = … of the particles and the medium

g = … constant

η = … of medium

sedimentation, diameter, density, gravitational, viscosity

To increase stability:

• … particles

• … viscosity

• … density difference (this is rarely done)

Smaller, Increase, Decrease

The viscosity cannot be too high that it prevents easy … and … of the suspension 

pouring, re-dispersion

One should avoid reducing the particle size too much because fine particles have a tendency to form a … upon settling to the bottom of container  

compact cake

Flocculating agents: form “…” between particles

bridges

Wetting agent: to help the drug particles to be suspended …

homogeneously

Which of the following regarding suspension is true?

a. Less preferred by children over tablet

b. Lack of dosage flexibility

c. Shake before taking the dose

d. Preservatives are included to improve the palatability

c

HJ has just gotten bitten by mosquitoes and has severe itch. HJ grabs a bottle of calamine suspension (calamine 8%). The ingredients show: zinc oxide 8%, bentonite, purified water, glycerin, and calcium hydroxide. What are the functions of glycerin and bentonite?

a. Glycerin: wetting agent; bentonite: flocculating agent

b. Glycerin: antioxidant; bentonite: preservative

c. Glycerin: thickening agent; bentonite: active ingredient

d. Glycerin: flavoring agent; bentonite: emulsifier

a

What are the purposes of including a flocculating agent and a wetting agent in a suspension?

a. Prevent caking of suspension

b. Improve palatability

c. Improve stability and dose uniformity

d. Improve microbiological stability

c 

Which of the following is not a typical characteristic of a pharmaceutical suspension?

a. Must remain uniformly dispersed indefinitely without shaking

b. Contains solid drug particles dispersed in a liquid

c. Requires shaking before use to redistribute particles

d. Particle size typically in the micron range

a

A major advantage of a suspension is:

a. Provides drug in a dissolved, stable form

b. Allows delivery of poorly water-soluble drugs

c. Requires no patient counselling

d. Never requires shaking

b

A preservative is added to suspensions to:

a. Improve flow properties

b. Prevent microbial contamination

c. Enhance sedimentation

d. Act as a suspending agent

b

According to the Stoke’s law, what formulation parameter of a suspension will lead to improved stability?

a. Increased particle size

b. Increased viscosity

c. Increased pH

d. Increased temperature

b

To ensure accurate dosing of a suspension:

• A suspension should settle … and should be readily … upon gentle shaking of the container 

• The particle size of the suspension should remain fairly … throughout long periods of undisturbed standing 

• The suspension should pour … and … from its container 

slowly, re-dispersed, constant, readily, evenly 

Storage of suspensions:

• …, …-resistant container

• …

Airtight, light, refrigerator

Dispersed phase = … phase

internal

Dispersing phase = … phase or … phase

external, continuous

What test can you use to determine the emulsion type?

Dilution test

What are the 2 main formulations of emulsions?

Liquid and semisolid 

Oral (o/w) vs. oral oil

• Better …

• Better absorbed due to … particle size

• Better …

taste, decreased, efficacy

Topical (w/o) vs topical water solution

• Better … by the skin due to … particle size

• … to the skin due to water soluble API is decreased

• w/o emulsion is more … with skin

• More … to dryness

absorption, decreased, Irritating, compatible, resistant 

Interfacial film:

• …: acacia; agar. o/w

• …: gelatin; egg yolk. o/w

• Finely divided solids: …; magnesium hydroxide

Carbohydrates, Proteins, bentonite 

Oriented-wedge (monolayer) surfactants:

• … molecular weight alcohols: cetyl alcohol; stearyl alcohol.

• Phospholipids: …

• Anionic, cationic and nonionic surfactants.

  • … combine anionic and cationic agents

High, lecithin, Cannot

Name 2 anionic agents

Triethanolamine oleate and sodium lauryl sulphate

Name a cationic agent

Cetylpyridinium chloride

Name 2 nonionic agents

Sorbitan esters and polyethylene derivatives (e.g. Span and Tween)

All of the following are nonionic surfactants, EXCEPT:

a. Cocamide

b. Tween

c. Alkyl polyethylene oxide

d. Poloxamer

e. Cetylpyridine chloride

e

Which of the following is a surfactant?

a. Sodium benzoate

b. Lectin

c. Ethanol

d. Benzalkonium chloride

e. EDTA

d

An emulsifier should promote emulsification and maintain … of the emulsion

stability 

What are the 5 types of physical instability of emulsions?

Coalescence, flocculation, creaming, breaking, and phase inversions

In coalescence and flocculation, the dispersed phase form … of …

aggregates, globules

In creaming, large aggregates … to the top or … to the bottom

rise, fall

In breaking, the liquid of the dispersed phase … and forms a … layer

separates, distinct

Which physical instability is irreversible?

Coalescence and breaking

Which physical instability is reversible?

Flocculation and creaming

Uneven drug concentration → … dose

inaccurate

To improve emulsion stability:

• Avoid extreme … and …

• Avoid … and …

• Minimal stability requirement: … months at … degrees C

• Others:

  • …-resistant container

  • Addition of … (e.g. ascorbic acid)

  • Antimicrobial 

heat, cold, freezing, thawing, 3, 5-40, light, antioxidant

Antimicrobial agents in emulsions:

• … contamination dominates, and normally occurs in the … phase

• …, …, or …% alcohol is included in the aqueous phase

• … doesn’t need preservatives

Fungi, water, Methylparaben, propylparaben, 12-15, oil

What is the advantage of using a topical water-in-oil emulsion?

a. It can allow drugs that are irritating to the skin to be kept within the continuous phase

b. It can improve absorption due to the increased size

c. It can mask the bitter taste of the medication

d. It can prevent moisture loss from the skin surface

d

Which of the following regarding stability of emulsion is correct?

a. Fungal contamination dominates.

b. Hydrophobic anti-microbial agents should be used to improve stability.

c. If the water phase is separated from the oil phase, advise to shake the emulsion before using it.

d. Store emulsion in a freezer to increase the shelf-life.

a

A water-in-oil (W/O) emulsion would be most suitable for:

a. Oral syrups

b. Injectable suspensions

c. Topical creams for dry skin

d. Inhalation products

c

During storage, an oral emulsion shows visible separation into two distinct layers that cannot be re-dispersed by shaking. This is an example of:

a. Creaming

b. Breaking

c. Coalescence

d. Flocculation

b