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Pharmaceutical Technology > Solutions > Flashcards

Solutions Flashcards

1
Q

What are some advantages of pharmaceutical liquids?

A

*easier administration
*increased rate of drug absorption
*high bioavailability if IV
*taste of medicines masked

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2
Q

What are some disadvantages of pharmaceutical liquids?

A

*difficult to formulate drugs that possess poor chemical stability
*difficult to formulate liquids for drugs with poor solubility
*require specialist formulation techniques

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3
Q

What factors affect drug solubility?

A

*crystal/liquid properties
*hydration
*molecular size
*properties of solvent
*pH of solvent

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4
Q

What are the effects of substituents on solubility?

A

*substituents can have effect on properties of the solid or liquid- molecular cohesion
*substituents have different interactions with water molecules
*substituents can be classified as hydrophobic or hydrophilic
*N, O containing molecules are hydrophilic
*position of substituents can effect stability- para has low solubility due to greater stability of crystalline structure

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5
Q

What does solvation mean?

A

Binding of solvent to solute

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6
Q

What is hydration?

A

Binding of water to solute

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7
Q

Are acids more soluble in acidic or basic solutions?

A

Basic

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8
Q

What is the equation for the dissociation of acid in water?

A

HA + H20 >< H3O+ +A-

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9
Q

What is the equation for dissociation constant in acids?

A

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

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10
Q

What is the equation for solubility of a base in water?

A

RNH2 + H20 ><RNH3+ +OH-

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11
Q

What is the equation for solubility of a base?

A

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

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12
Q

What is an amphoteric drug?

A

One that possesses both acidic and basic properties

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13
Q

What is the generalised structure of an amphoteric drug?

A

RXNH2COOH

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14
Q

What is the structure of RXNH2COOH at low pH?

A

RXNH3+COOH

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15
Q

What is the structure of RXNH2COOH at high pH?

A

RXNH2COOH-

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16
Q

What is the zwitterion of RXNH2COOH?

A

RNXH3+COO-

17
Q

How do you calculate the % ionisation of a drug given pH and concentration?

A
  1. Convert pH to [H+
    pH is -log[H+]
    so do 1/10^pH
    then x1000 to give in mmol
  2. Use given concn or calculate [HA]
  3. Calculate %ionisation by doing [H+]/[HA] x 100
18
Q

What is a co solvent?

A

Substances added to primary solvent (water) to increase the solubility of poorly water soluble drug.
Examples- ethanol, glycerol, propylene glycol

19
Q

What is the solubility parameter?

A

Thermodynamic measure of cohesive forces in a substance
Maximum solubility= Solubility parameters of solvent and solute identical

20
Q

What is the dielectric constant?

A

Maximum solubility is achieved in a solvent at defined dielectric constant.
Dielectric constant is Cx (material in condenser)/ Co (standard).

21
Q

What is a surfactant and how does it improve solubility?

A

Surfactants reduce surface tension and increase spreading/wetting properties.
*examples= spans, tweens, phospholipids (in combination)
*used for vitamins and steroids

22
Q

What is a hydrotrope?

A

Compound that solubilises hydrophobic compounds in aqueous solutions by means other than micellar solubilisation. Hydrotropy is the process of adding a secondary solute which increases aqueous solubility of the primary solute.

23
Q

What are examples of hydrotropes?

A

Sodium benzoyl
Sodium salicylate

24
Q

What are methods used to increase solubility of drugs?

A

*hydrotropy
*cyclodextrins
*surfactants
*co-solvents

25
Q

What are added excipients in liquids?

A

*vehicle
*preservatives- parabens, benzoic/sorbic acid, benzyl alcohol
*sweetening agents- sucrose common but can cause cap locking.
, aspartame and saccharin.
*viscosity control-optimise pourability. Hydroxyethyl or …cellulose. Modify sugar conc
*flavours-menthol, chloroform
*colours

Pharmaceutical Technology (21 decks)

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