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Pharmaceutical Technology > Solutions > Flashcards

Solutions Flashcards

1
Q

What are advantages of liquids?

A

*ease of administration
*increased drug absorption
*high bioavailability if administered IV
*taste masking

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2
Q

What are disadvantages of liquids?

A

*hard to formulate drugs with poor chemical stability-specialist techniques needed
*need special formulation strategies I,e taste masking, appearance, viscosity

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3
Q

What factors affect drug solubility?

A

*hydration
*structural features - substituents
*molecular size
*pH of solvent
*crystal/ liquid properties
*solvent properties

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4
Q

How do substituents influence solubility of molecules in water?

A

*its effect on solid/liquid properties- molecular cohesion
*effect of its interaction with water molecules
Substituents classified as either hydrophobic or hydrophilic

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5
Q

What are examples of hydrophilic substituents?

A

OH
NH2
NO2
COOH

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6
Q

Why would a para compound possess low solubility properties?

A

Para compounds have greater stability in their crystalline states

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7
Q

What is hydration?

A

Binding of water to solute

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8
Q

What conditions are acids more soluble in?

A

Basic
Dissociated species can interact

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9
Q

What is the equation for the dissociation constant of an acid? (Ka)

A

Ka= [H3O+][A-]/ [HA]

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10
Q

What is the equation of an acid dissociating in water?

A

HA + H2O >< H3O+ + A-

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11
Q

What is the equation of a base dissociating in water?

A

RNH2 + H20>< RNH3+ + OH-

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12
Q

What is the equation for the dissociation constant of a base (Kb)?

A

Kb= [RNH3+][OH-]/ [RNH2]

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13
Q

What is an amphoteric drug?

A

Drug posses acidic and basic properties.

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14
Q

What are the two dissociation constant equations for amphoteric drugs?

A

Ka1= [HA+-][H+]/[HAH+]
Ka2= [A-][H+]/[HA+-]

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15
Q

What is the equation for % ionisation?

A

[H+]/ [HA] x100

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16
Q

What is a co- solvent?

A

Substance added to primary solvent (water) to increase solubility of poorly water soluble drug
Eg glycerol , ethanol

17
Q

What two methods used to predict solubility of a solution?

A

*solubility parameter- thermodynamic measure of cohesive forces in a substance
Max solubility- parameters of solute and solvent identical
*dielectric constant- max solubility at a defined dielectric constant

18
Q

What is a surfactant?

A

Substance that reduces surface tension between two liquids or solid and liquid
Increase solubility
Combinations- tweens, spans, phospholipids
Used for vitamins and steroids

19
Q

What is a hydrotrope?

A

Substances that solubilise compounds by means other than surfactant/micellar mechanism
(Salts with large anions or cations)
Eg sodium benzoate

20
Q

What is a disadvantage of using a hydrotrope?

A

Large amounts required (20-50%)

21
Q

What are required properties that a preservative should have?

A

*broad spectrum efficacy
*physically, chemically and biologically stable over shelf life
*non toxic, physiologically and physio chemically inert

22
Q

What are examples of preservatives?

A

*parabens
*benzoic/sorbic acid

23
Q

What are examples of sweetening agents used in solutions?

A

*Sucrose- can be combined with other polyols (polyols reduce cap locking (sugar crystals on cap)).
*liquid glucose
*saccharin- sugar alternative
*aspartame- sugar alternative (200x sweeter than sucrose)

24
Q

What are examples of flavours used in solutions?

A

*menthol/chloroform- mild anaesthetic effect on sensory receptor organs
*monosodium glutamate- reduces bitterness

25
Q

How is viscosity control achieved?

A

Modification of sugar concentration or hydrophilic polymers
Eg hydroxypropylcellulose

26
Q

How do you calculate % ionisation of an acid?

A

Given PKA and pH
Start with Equation: pH=PKA + log[A-/HA]
NOTE: [A-] and [H+] are same thing

rearrange:
pH-pKa (X) =log[A-/HA]

Do shift log^X= [A-] aka H+

Add 1=[HA]

So end equation is [H+]/[HA] x100 = % ionisation

NOTE if given pH and PKA the same, % ionisation is 50%

Pharmaceutical Technology (21 decks)

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