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Dosage Forms II > Solution and Emulsion > Flashcards

Solution and Emulsion Flashcards

Exam 1 Content

1
Q

What is a solution?

A

homogeneous molecular dispersion (everything is dissolved to a molecular level)

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2
Q

What is an emulsion?

A

oil in water, water in oil LIQUID IS SUSPENDING

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3
Q

What is a suspension?

A

solid in water or oil, SOLID IS SUSPENDING

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4
Q

Advantages of solutions?

A
  1. Homogeneous- no problems of content uniformity
  2. Easy to manufacture
    3.Good bioavailability
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5
Q

Two things to know in designing a buffer

A

Buffer principle and buffering capacity

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6
Q

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

A

That is when the buffering capacity is at its highest (Meaning that the acid can help the solution resist a change in pH better)

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7
Q

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

A

1.Minimize buffering capacity
2.Minimize volume
3.Administer slowly

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8
Q

Antimicrobial preservatives mechanism of action

A
  1. Absorb into the bacterial membrane and disrupt it (membrane is lipophilic and negative charge)
  2. Absorption due to lipid solubility (alcohols, acids, esters)
  3. Absorption due to electrostatic interaction (quaternary ammonium compounds are positively charged)
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9
Q

When are preservatives supposed to be used?

A

When drugs are intended to be used MORE THAN ONCE

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10
Q

What are the desirable products of preservative?

A

-Effective in low concentrations against a wide variety of organisms
-Soluble in formulation
-Non-toxic
-Stable

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11
Q

What are the four kinds of antimicrobial preservatives?

A
  1. Alcohols
  2. Acids
  3. Esters of p-hydroxybenzoic acid (Parabens)
  4. Quaternary Ammonium Compounds
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12
Q

How do ALCOHOLS act as a microbial preservative?

A

They interact with the cellular membrane, preventing bacteria from working by binding to the membrane through lipophilic interactions

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13
Q

What are the types of alcohol based preservatives?

A

Ethanol, Benzyl Alcohol, Chlorobutanol

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14
Q

What are the characteristics of ethanol?

A

PRESERVATIVE
Requires greater than 15%, limited to oral products and can be lost due to volatility (losing content whenever the drug is reopened and closed)

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15
Q

What are the characteristics of benzyl alcohol?

A

PRESERVATIVE
Has a local anesthetic action, burning taste and can’t be used orally
Water soluble and STABLE OVER WIDE PH RANGES

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16
Q

What are the characteristics of chlorobutanol?

A

PRESERVATIVE
Not used orally, used in parenteral and ophthalmics
Volatile (content can be lost through rubber stoppers and plastic containers)

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17
Q

What are the characteristics of acid based preservatives?

A

Only active in unionized (lipid-soluble) forms

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18
Q

What are types of acid based preservatives

A

Benzoic Acid and Sorbic Acid

19
Q

What are the characteristics of benzoic acid?

A

-PRESERVATIVE
-pKa = 4.2 and is used in oral products
-Means that this is effective in solutions w/pH LOWER than 4.2

20
Q

What are the characteristics of sorbic acid?

A

-PRESERVATIVE
-pKa = 4.8 and used in oral products
-Works in solutions that are 4.8 and LOWER
-Effective in molds and yeast

21
Q

What are the characteristics of esters of p-hydroxybenzoic acid (Parabens)?

A

-Widely used orally and hydrolyzed rapidly at pH values ABOVE 7
-anesthetized tongue
-problem with low solubility
-cause skin sensitization when used in dermatological products

22
Q

Propyl and butyl parabens

A

MOST lipophilic and are best against molds and yeast

23
Q

Methyl paraben and ethyl paraben

A

LEAST lipophilic ones and best against bacteria

24
Q

What are the characteristics of quaternary ammonium compounds?

A

-PRESERVATIVE
-used in ophthalmics since they are water soluble and fast killing
-does have compatibility issues due to POSITIVE charge
-can’t be used in injectables since it can damage host cells

25
Q

What are the examples of quaternary ammonium compounds?

A

Benzalkonium chloride (Zephirin) and Cetyltrimethylammonium chloride (Cepryn)

26
Q

What is the MOA of quaternary ammonium compounds?

A

interact with the membrane through electrostatic interactions (since they have a positive charge and the membrane has a negative charge)

27
Q

Factors affecting preservative action

A

-pH
-complex formation
-absorption of solids
-chemical stability

28
Q

What is the purpose of antioxidants?

A

Battle oxidation since it is the main degradation pathway of pharmaceuticals

29
Q

Types of antioxidants?

A

Free radical scavengers, reducing agents, chelating agents

30
Q

The MOA of free-radical scavengers

A

Delay oxidation by rapidly reacting with free radicals

31
Q

Examples of free-radical scavengers

A

-Propyl, octyl, dodecyl esters of gallic acid
-butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT)
-Tocopherols (Vitamin E)

32
Q

MOA of reducing agents

A

Have lower redox potentials and are more readily oxidized (get oxidized first so the drug itself doesn’t get oxidized)

33
Q

Examples of reducing agents

A

Sodium bisulfite, ascorbic acid, and thiols

34
Q

MOA of chelating agents

A

These are agents that removes trace metals that are involved in oxidation

35
Q

Examples of chelating agents

A

Citric acid and EDTA

36
Q

What is an emulsion?

A

this is a system of two immiscible liquids in which one is dispersed as droplets (O/W) and (W/O)

37
Q

Characteristics of Oil in Water O/W

A

oil is DISPERSED in water

38
Q

Characteristics of Water in Oil W/O

A

water is DISPERSED in oil

39
Q

How are emulsions used orally?

A

-primarily O/W
-used to mask the taste of oil by hiding the properties in water
-enhance the absorption of an oil (when the drug isn’t water soluble)

40
Q

How are emulsions used externally?

A

-mostly cosmetically
O/W- is water washable (seems more watery)
W/O- for cleansing skin (seems more oily)

41
Q

How are emulsions used intravenously?

A

-O/W is the type of emulsion that’s used
-the oil droplets must be very small so it doesn’t block the blood vessel (<1um)
-used for parenteral nutrition

42
Q

What is interfacial tension?

A

The force of tension per unit length of interface

43
Q

Basis of interfacial tension

A

-describes how molecules spread
-ex; oil spreads better due to lower surface tension while water doesn’t spread b/c it doesn’t like to interact w/air which means increased surfaced tension (aggregate)

Dosage Forms II (8 decks)

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