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Pharmacology & Pharmaceutical Science > Preformulation > Flashcards

Preformulation Flashcards

(63 cards)

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1
Q

Define formulation

A

The process of developing a drug candidate into a drug product

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2
Q

Define Preformulation

A

An investigation of physical and chemical properties of a new chemical entity, alone and when combined with excipients to identify suitability of the new chemical entity to develop an efficacious dosage form.

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3
Q

What objectives are targeted during Preformulation?

A

Stability
Bioavailability
Can be mass produced

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4
Q

Name 4 organoleptic properties

A

Odour
Colour
Taste
State

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5
Q

Name 5 bulk properties

A

Melting point
Crystallinity and polymorphism
Hygroscopicity
Fine powder characterisation
Powder flow properties

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6
Q

What does melting point tell us?

A

The purity of the compound
Its thermal properties
Clues about state of solvation, polymorphism.

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7
Q

How do you determine what kind of solid you have?

A

Measure melting point
Visual inspection
Measure crystal structure using x ray diffraction

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8
Q

What are the two classifications of solid drugs?

A

Crystalline
Amorphous

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9
Q

Define crystal

A

Highly ordered arrays of atoms, ions or molecules

Held together by van der waals, ionic or h bonds

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10
Q

Define crystal lattice

A

Molecular arrangement within the solid crystal

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11
Q

Define crystal habit

A

Description of the outer appearance of the crystal

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12
Q

Define unit cell

A

The smallest portion of the crystal lattice that shows the 3d pattern of the entire crystal.

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13
Q

What are the 3 types of crystalline solids?

A

Ionic
Atomic
Molecular

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14
Q

Which type of crystal is easiest to inject?

A

Platelike crystals

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15
Q

Which type of crystal flows the best?

A

Equidimensional crystals have the best flow properties

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16
Q

What alters crystal form?

A

Surfactants in the solvent medium used for crystal growth can alter crystal form by growing faces during crystal growth

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17
Q

What two processes control crystallisation?

A

Nucleation
Growth

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18
Q

What 4 methods proceed crystals?

A

Supersaturation
Cooling
Evaporation of solvent
Chemical reaction

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19
Q

Define amorphous

A

Solids consisting of molecules arranged in a random manner.
They flow when subjected to sufficient pressure over a period of time.
They do not have melting points.

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20
Q

Define polymorphs

A

Crystals that contain the same molecular species but they have different unit cells.

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21
Q

Why is polymorphism important?

A

Polymorphic forms must be characterised and the medicine should only contain one specific polymorph with the desired properties.

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22
Q

How are polymorphs identified?

A

X ray diffraction, IR spectrum Melting point and dissolution rate.

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23
Q

Define Pseudo-polymorphism

A

Phenomenon in which solvent molecules get incorporated into crystal lattice of the solid, forming solvates.

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24
Q

What happens when polymorphic solvates are heated compared to pseudo polymorphic solvates?

A

Polymorphic solvates change crystal structure when heated.
Pseudo polymorphic solvates do not change crystal structure when heated

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25
Define thermal gravimetric analysis
A technique in which the weight changes in a material is measured as a function of temperature or time.
26
Define differential scanning calorimetry
A thermal analysis technique used to measure how a physical property of a sample changes with temperature against time.
27
Define X-ray diffraction
A technique providing details information about crystallographic structure and chemical composition. As well as size, shape and crystal orientation
28
Define solubility
The concentration of a solute in a saturated solution at a certain temperature.
29
Define solubilisation
The preparation of a thermodynamically stable solution of a substance which is normally insoluble or very slightly soluble, in a given solvent by the introduction of an additional component.
30
Define dissolution
The process in which a solid substance solubilises in a given solvent.
31
Define dissolution rate
The amount of solid substance that goes into solution per unit time under standard conditions
32
Why is solubility important
Drugs must dissolve to be absorbed. Solubility affects release into dissolution media and bioavailability.
33
Define saturated solution
A solution containing the maximum concentration of a solute dissolved in the solvent
34
Define unsaturated solution
A solution where the solute concentration is lower than its solubility
35
When will a substance dissolve in a solvent?
When the attractive forces between the solute and solvent molecules are greater than those between solute molecules or solvent molecules
36
How is solubility determined?
Make a saturated solution at a given temperature Remove excess undissolved solid Determine concentration of saturated solution by UV, titration, HPLC.
37
What factors affect solubility?
Temperature Solvent pH Solvent composition Particle size and shape Physical form of drug and pKa
38
What do surfactants do?
Reduce surface tension
39
What are surfactants?
Amphiphilic molecules composed of hydrophilic polar head and hydrophobic non polar tails.
40
How does pH influence solubility?
PH affects drugs that have ionisable groups. The degree of ionisation which solubility depends on is determined by pH. Ionised forms of drugs tend to be more soluble.
41
How does heat influence solubility?
Heat breaks bonds. Heat is given off when bonds between solute and solvent are formed . Solubility increases wit temperature in most solids
42
What are the two methods of enhancing solubility?
Physical modifications Chemical modifications
43
Name 4 physical modifications
Solubilisation by surfactants Particle size reduction Modification of crystal habit Drug dispersion in carriers
44
Name 3 chemical modifications
Change in pH Salt formation Complexation
45
Describe biological membranes
Lipophilic so can absorb lipophilic molecules but not ions.
46
How is absorption characteristics of a drug determined?
The oil water partition coefficient, P
47
How do you know is a drug is lipophilic?
P >1.0
48
How do you know a drug is hydrophilic?
P<1.0
49
Describe drugs with high log P
Protein bound Low aqueous solubility Bind to extraneous sites
50
Describe drugs with low log p
Too hydrophilic to have any affinity for the membranes May be poorly absorbed
51
Why are co-solvents used?
If a drug is insoluble in water a co-solvent is added to make the drug dissolve. The drug must be more soluble in the co-solvent The co- solvent must be miscible with water
52
Name 5 co-solvents
Water Glycerine Propylene Ethanol Polyethylene glycol
53
Name 3 types of chemical degradation
Oxidation Hydrolysis Isomerisation
54
What groups are prone to oxidation?
Phenols Aromatic amines Catechols Polyunsaturated fats and oils
55
Why are these drugs prone to oxidation?
Their chemical structure contain electron rich groups making them more reactive with oxygen
56
What drugs are susceptible to hydrolysis?
Carboxylic acid Ketone
57
58
How to protect against oxidation?
Exclusion of oxygen Coloured glass containers Antioxidants
59
How to protect against hydrolysis?
Determine pH of maximum stability Use non aqueous solvents Lower the solubility Prepare medicine immediately prior to use
60
Why is stability testing important?
To determine storage conditions Suitability of ingredient To predict shelf life Qc purposes
61
What does shelf life depend on?
Storage conditions Type of drug Obvious colour change accompanies degradation Toxic degradation products
62
What factors must be defined 8mg protocols are constructed?
Temperature of storage Relative humidity of storage Suitable light challenge Sampling times No. Of batches tested on No. Of repeats in each batch Suitable assay
63
What’s are the suitability testing guidelines?
Long term and accelerated testing required 3 batches of product must be tested Products stored in usual containers Testing must cover all features expected to change during storage

Pharmacology & Pharmaceutical Science (6 decks)

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