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829 - Dosage Forms II > Exam 1 > Flashcards

Exam 1 Flashcards

1
Q

What are the types of liquid dosage forms?

A

Solution - Homogenous molecular dispersion, making the liquid transparent. The drug is dispersed to a molecular level.

Emulsion - The liquid isn’t homogenous. A liquid is suspending in another liquid (ex. o/w = oil suspending in water).

Suspension - A solid is suspending in the liquid (Ex. solid in water).

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2
Q

What are the advantages of solutions? (3)

A
  • Homogenous, so there’s no problems of content uniformity
  • Easy to manufacture
  • Good bioavailability because the drug is already dissolved
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3
Q

What are the 2 things to keep in mind when designing a buffer?

A

1

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4
Q

Why is a weak acid with a pKa close to the desired pH selected?

A

The buffering capacity is highest when the pH of solution is closest to the pKa of the weak acid, and if the buffering capacity is higher, that means we can use less of it.

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5
Q

How can you design a buffer with a specific pH and buffering capacity?

A

You can choose the weak acid that is closest to the desired pH, then, using the buffering capacity, you can calculate the ratio of the acid/base and find the amount of each that are needed for the buffer.

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6
Q

What needs to be done to minimize irritation if pH of solution cannot match the pH of the body fluid?

A

To minimize irritation with a parenteral, opthalmic, or nasal dosage form, we want to adjust the pH to be the same as the pH of the bodily fluid. If we can’t:

Minimize buffering capacity, minimize volume, and administer slowly.

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7
Q

What’s the mechanism of action of antimicrobial preservatives?

A

Preservatives make a thin layer around the bacterial membrane and disrupt it. These are used to protect the patient from pathogens and to maintain potency and stability of dosage forms.

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8
Q 
What are the functions of these classes of excipients: 
Co-solvent
Buffering agent
Preservative
Antioxidant
Chelating agent
Flavor
A

Co-solvent - Used when the drug isn’t very soluble in water (ethanol, glycerin, propylene glycol)

Buffering agent - Helps maintain the pH of a substance.

Preservative - Protects the patient from pathogens and maintains potency/stability of dosage forms.

Antioxidant - Used to prevent chemical reactions

Flavor - Can change to make it taste good

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9
Q

What is the Handersen-Hasselbach equation? What is the equation to find Ka?

A

pH = pKa + log[A-/HA]

Ka = ([H+][A-]/[HA])

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10
Q

What group do these belong to: Acetic acid, citric acid, glycine, phosphoric acid

A

These are common buffers

Citric acid and phosphoric acid both have 3 ionization states

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11
Q

What makes the ideal preservative? (4)

A

They are effective at low concentrations
Soluble in formulation
Non-toxic
Stable

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12
Q

What group do these belong to: Ethanol, benzyl alcohol, chlorobutanol

A

Preservatives - Alcohol

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13
Q

What group do these belong to: Unionized acids like benzoic acid, sorbic acid

A

Preservatives - Acids

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14
Q

What group do these belong to: Esters of p-Hydroxybenzoic acid like propyl paraben, butyl paraben, methyl paraben, ethyl paraben

A

Preservatives - Parabens

More lipophilic = best against mold and yeast
Less lipophilic = best against bacteria

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15
Q

What group do these belong to: Benzalkonium chloride, Cetyltrimethylammonium chloride

A

Preservatives - Quaternary ammonium compounds

These are very water soluble and widely used in opthalmics

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16
Q

What group do these belong to: Propyl, octyl, dodecyl esters of gallic acid, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), tocopherols like Vitamin E

A

Antioxidants - Free radical scavengers

These get rid of free radicals

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17
Q

What group do these belong to: Sodium bisulfate, ascorbic acid, thiols

A

Antioxidants - Reducing agents

These react with oxygen before the chemicals in the body do

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18
Q

What group do these belong to: Citric acid, EDTA

A

Antioxidants - Chelating agents

Gets rid of the metals to reduce the frequency of oxidation

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19
Q

What is an emulsion and what are the types of emulsions?

A

Emulsion - A system of two liquids that can’t mix together, so one is dispersed as droplets in the other.

Types: O/W (oil in water) & W/O (water in oil)

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20
Q

What are the clinical applications of emulsions? (Oral, external, IV lipid emulsion)

A

Oral - O/W used to mask the taste of an oil and enhance the absorption of an oil.

External - O/W vanishing cream, and other water-washable things. W/O for cleansing skin like a cold cream.

IV lipid emulsion - O/W for parenteral nutrition (but it’s critical that the droplet sizes are less than 1 mcg to avoid embolisms)

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21
Q

What is the molecular basis of interfacial tension and how do surfactants alter the interfacial tension?

A

Molecules at the interface experience different forces than those in the bulk phase. This imbalance leads to spontaneous movement of molecules going from the interface to the bulk phase, thus leaving fewer molecules per unit area at the interface.

The force of the tension in all directions while the molecules are trying to resist expansion is called interfacial tension.

Surfactants interact with water and oil, stabilizing the oil and water phase and thus reducing interfacial tension. They act as a clamp binding oil and water together.

22
Q

What is the role of interfacial tension in the production of an emulsion and stability of an emulsion?

A

The higher the interfacial tension, the less stable the emulsion will be. Emulsifying agents will be added to emulsions to reduce the interfacial tension, thus stabilizing the emulsion.

23
Q

Why do micelles form in solutions of surfactants and what’s the utility of them?

A

Micelles are formed when you add more and more of the surfactant because a micelle is most stable, and then the surface tension will no longer decrease, because the “extra” surfactant is just making a micelle and no longer functioning as a surface tension stabilizer.

The micelle is a lipid-like region that is capable of dissolving water-insoluble drugs.

24
Q

What are emulsifying agents and what is the mechanism where surfactants, hydrophilic colloids, and finely divided solids act as emulsifying agents?

A

Emulsifying agents are agents that are added to stabilize the emulsion.

Surfactants - These molecules have a hydrophobic and a hydrophilic end. They will orient themselves in the desired position and by doing that, will lower interfacial/surface tension.

Hydrophilic colloids - Used in O/W emulsions. They are long hydrophilic polymers that form a film at the interface and increase the viscosity of water. However, this doesn’t lower interfacial tension, it just reduces the like-like clumps of water or oil.

Finely divided solid particles - These are small particles that form a film along the interface.

25
Q

What is the basis of physical instability of emulsions? (3 types)

A

Creaming - The dispersed particles will settle due to gravity. This is usually fine, as long as the particles haven’t degraded/changed.

Coalescene - Oil droplets merging together to make bigger droplets because the interfacial film is unable to maintain the integrity of the individual droplets. This is irreversible and the emulsion must be reformulated.

Phase inversion - This happens when the phase volume ratio exceeds 74% (you usually want to keep it below 50%). This can be due to degradation/conversion while the emulsion sits.

26
Q

How can you predict the type of emulsion by inspecting the formula?

A

The phase in which the emulsifier is most soluble will be the continuous phase. You can tell where it’s most soluble by the HLB value (<10 means oil-like, >10 means water-like).

We know hydrophilic colloids are only in O/W.

If the contact angle with finely divided solids is <90º, it’ll be hydrophilic (water). More than 90º means hydrophobic (oil).

We can also look at the phase volume ratio which is: volume of oil phase / total volume of emulsion. 0-26% = O/W; 26-74% could be either one; 75%-100% is W/O only.

27
Q

What are the typical components of an emulsion and how do you manufacture an emulsion?

A
  1. Dissolve all water-soluble ingredients in water
  2. Mix all oil-soluble ingredients in oil.
  3. Heat aqueous solution to same temp as oil solution.
  4. Mix solutions together.
  5. Cool slowly.
  6. Pass through a colloid mill or homogenizer to produce a finely dispersed immersion.
28
Q

What is the HLB equation of a mixture and what does it tell us?

A

HLB = aX + (1-a)Y

it tells us how hydrophilic/lipophilic the mixture is so that we know what surfactant to use depending on if the emulsion is O/W or W/O.

29
Q

What group do these belong to: Alkyl sulfate, Alkyltrimethylammonium bromide, Alkyl betaine, Alcohol ethoxylate

A

Emulsifier - Surfactant

30
Q

What group do these belong to: Acacia, tragacanth, gelatin

A

Emulsifier - Hydrophilic colloids

31
Q

What group do these belong to: Charcoal, Bentonite, magnesium aluminum silicate, aluminum hydroxide

A

Emulsifier - Finely divided solid particles

32
Q

What group do these belong to: Cetyl alcohol, sodium dodecyl sulfate, stearyl alcohol, polysorbate 60, sodium lauryl sulfate

A

Emulsifier

33
Q

What group do these belong to in the context of emulsifiers: glycerin, propylene glycol

A

Humectant (emulsifer that holds onto water)

34
Q

Why would you select a suspension dosage form rather than a solution?

A

A suspension displays zero order kinetics of degradation, meaning it degrades slower. Also, when the particles aren’t soluble, it’ll have to be a suspension. Lastly, suspensions can taste better than the solution form.

35
Q

When is a suspension preferred over a tablet dosage form?

A

Suspensions have more flexibility in dosing, they are easier to swallow, and they have a faster dissolution rate because the particles are already so small.

36
Q

What are the desirable properties of an ideal suspension?

A

The suspended material shouldn’t settle quickly, but when they do, they should be easily redispersed when shaken.

Should be easy to administer, meaning not too viscous and not to fluid.

Particle size needs to remain constant during storage. Shouldn’t be any aggregation over time.

37
Q

Based on the Stoke’s Law, what factors affect the velocity of sedimentation of a suspension dosage form?

A

The size of the particle
The difference in densities between the solid and liquid
The viscosity of the liquid

38
Q

What are the common methods of a particle size reduction?

A

Micropulverization - 10-50 mcg; This is using high speed attrition or impact mills

Fluid energy grinding - <10 mcg; Jet milling, micronizing, shearing action of high-velocity compressed airstream on the particles in a confined space.

Spray drying - <5 mcg; Cone-shaped apparatus in which a solution of a drug is sprayed and rapidly dried by a warm, dry air circulating in the cone.

39
Q

What processes occur during aging of a suspension to bring ΔG toward zero?

A

The particles in the suspension want to decrease their surface area to bring ΔG toward zero. To do this, they undergo aggregation and crystal growth.

40
Q

What are the important interparticle forces in suspension dosage forms?

A

Van der Waals attractive force - Always present, increases as distance gets smaller. Not affected by formulation factors.

Hydration repulsive force - Due to absorbed water molecules at the surface of a particle. Not affected by formulation factors.

Electrostatic repulsive force - Due to surface charge on the particles. May be controlled by the formulation.

Steric repulsive force - Due to an adsorbed layer of neutral polymer at the surface of a particle. May be controlled by the formulation.

41
Q

What’s the difference between dispersion and flocculation?

A

Dispersed - Unless the particles are really close, the net force will be repulsive. The particles repel each other and don’t aggregate. The problem with this is that particles settle as individual particles, leading to dense, compact sediment, which may be difficult to resuspend.

Flocculation - Repulsive and attractive forces are in balance. The particles are attracted to each other at the secondary minimum to form aggregates (known as floccules). The floccules settle to produce a sediment with a high volume.

42
Q

What is the basis of Newtonian and non-Newtonian flows?

A

Newtonian - As you apply greater stress, flow will increase proportionally.

Non-Newtonion - Includes simple plastic flow, simple pseudoplastic flow, and dilatant flow. These are non-proportional increases/decreases of the rate of shear as force is applied.

  • Plastic: Shear thinning
  • Pseudoplastic: Shear thinning
  • Dilatant: Shear thickening
43
Q

How can shear-thinning rheology be used to prepare suspensions?

A

2

44
Q

What are the different suspension approaches?

A

Dispersed suspension - Aim to achieve very slow rate of sedimentation. This will be a cloudy suspension with dense sediment. This may more a non-suspendable sediment (cake).

Controlled flocculation - Rapid rate of sedimentation. This will be a clear supernatant with large sediment volume. It will be easily redispersed by shaking.

Structured vehicle - May appear as semi-solid when undisturbed but is fluid when shaken. There’s no sedimentation because it’s so thick that the particles can’t settle. This is thixotropic, meaning after shaking is finished, it’ll get back to its rigid structure.

45
Q

What are the usual components of suspension dosage forms? (9)

A 
Active ingredient
Vehicle
Buffer
Preservative
Flocculating agent
Structured vehicle system
Wetting agent
Antifoaming agent
Flavor and sweetener
46
Q

What group do these belong to: Clay (diluted bentonite magma), alteration of pH, electrolytes, non-ionic or ionic surface active ingredients

A

Flocculating agents

47
Q

What group do these belong to: CMC, methylcellulose, microcrystalline cellulose, polyvinylpyrrolidone, xanthan gum

A

Structured vehicle - Polymer

48
Q

What group do these belong to: Bentonite, magnesium aluminum silicate

A

Structured vehicle - Clay

49
Q

What group do these belong to: Polysorbate 80

A

Wetting agent

50
Q

What is a polymer?

A

A large molecule made up of many small repeating untis. They are a subset of macromolecules.

51
Q

What are synthetic and natural polymers?

A

Synthetic - Man-made. Polyethylene, Nylon, etc.

Natural - In the environment. ex. RNA, DNA, proteins like gelatin, polysaccharides like cellulose.

52
Q

How do you name a polymer?

A

Poly(repeating unit)

Ex. polyhuman (humans are the repeating unit)

829 - Dosage Forms II (5 decks)

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