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PA20308 > Pharmaceutics > Flashcards

Pharmaceutics Flashcards

1
Q

When are preservatives not needed in elixirs?

A

When their alcohol % is over 12%

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2
Q

Define ‘Pseudopolymorphs’

A

When solvents are incorporated into the crystal structure

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3
Q

What is a bravasis lattice?

A

This is when molecules can be arranged differently inside of the same unit cell

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4
Q

What is cracking, in context of pharmaceutical emulsions?

A

The internal phase merge together, causing seperation of the two layers

Due to the destruction of the film at the interface between the droplet and external phase

Once this occurs, it cannot be recovered

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5
Q

What is the DLVO theory?

A

This is the theory that the overall energy of the interaction between particles is determined by the repulsive forces (zeta potential) and attractive forces (van der waals)

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6
Q

Which is the most common pathway of drug delivery via the epithelium?

And which drugs can use this?

A

Transcellular transport

Small lipophillic drugs

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7
Q

Why are lubriants used in the manufacturing of drugs?

And what is the most common?

A

To prevent adherance of the formulation to the punches and dies

Magnesium Sterate

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8
Q

What is the ideal phase:volume ratio for emulsions?

A

50:50

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9
Q

Why is granulation done?

A

To produce uniform and normalised particles with better flow and to increase its compressability

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10
Q

What are the 3 stages of compressing a powder bed?

A

Stage 1 - Rearrangment of a powder bed upon low stress, in order to minimise the free space between the particles

Stage 2 - Deformation of the powders due to the applied stress. This occurs when there is no more space for particles to fill. Best type is plastic deformation

Stage 3 - Bonding of the compressed powders via intermolecular forces, solid bridges and mechanical interlocking

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11
Q

What is a collodial suspension?

A

When the drug molecules are so small that they are unaffected by gravity, and do sedimentation cannot occur.

This leads to it being evenly distributed (uniform dose)

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12
Q

Define ‘Preformulation’

A

The characterising of the physical and chemical properties of the active pharmaceutical ingredients

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13
Q

What is the difference between paracellular and transcellular absorption?

A

Paracellular - Where molecules move between the cells –> eg, tight junctions and desmosomes Transcellular - Molecules pass through the actual cells that make up the membranes –> eg. transporters

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14
Q

What are the advantages of multi-particulates over tablets?

A

Their smaller size means that they can pass through the pyloric sphincter easier….so they’re less dependent of gastric emptying

Less likely to suffer from dose dumping

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15
Q

Give an example of how we could increase, or decrease the solubility of a solute

A

Increase - Use of a salt

Decrease - Esterification of the parent drug

This facilitates absorption of the drug in the GI, and also protects it from degradation

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16
Q

Define ‘Crystal Form’

A

The ordering of atoms and molecules to form a crystal structure

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17
Q

What is the main differences between hard shelled and soft shelled capsules?

A

Hard - Used for semi-solid fills and powders/beads and pellets

Soft - The drug is either dissolved, or suspended in a liquid phase

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18
Q

What is an amphiphile?

A

A molecule that contains both a hydrophillic and lipophillic part

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19
Q

What plays the largest role in effecting the velocity of sedimentation?

A

Viscoity of the solution

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20
Q

What are the 3 ways that the drug can be released from multi-particulates

A

Diffusion

Osmosis - Water enters causing the tablet to swell, pushing the drug out

Erosion

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21
Q

Which classes of drugs need to be modified for oral administration… and why?

A

Class 2 and 4

This is because these have low solubility

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22
Q

What is a glidant?

A

A flow agent

Done by reducing the contact area between granules

23
Q

What is a Miller Indice?

A

Something that is given to each different crystal face to identify them

24
Q

Explain the principle of ‘Co-solvency’

A

This is where multiple solvents are used to adjust the overall polarity. For example adding low polarity solvents to weaken the H bonding between the water. This works on the basis of Like dissolves like

25
Q

Why do drugs with less H-bonding potential have greater oral bioavaliability?

A

Because for drugs to be absorbed across a membrane, the H bonds formed between the drug and water must be broken first…. as water is very polar and so will not pass

26
Q

What is a diluent?

And what is the most common?

A

A bulking agent to make a fully sized tablet

Microcrystalline Cellulose (MCC)

27
Q

Explain the difference between a saturated, unsaturated (sub-saturated) and supersaturated solution

A

Saturated - When the solute is in equilibrium with the solvent Unsaturated - Where the concentration of the solute is lower than that needed for full saturation Supersaturated - Where there is more solute present than can be dissolved…..can be dissolved if tempreture is increased and then decreased

28
Q

Define ‘Polymorphism’ And what are the two sub types?

A

When a chemcial compound can exist in different crystal forms Stable (alpha) - These have high melting points, and so are less soluble Metastable (beta) - Lower melting point and unstable….so these are more soluble!!

29
Q

What is the Critical Micelle Concentration (CMC)? And what will affect it?

A

The concentration of the monomer at which micelles are formed

Increase - With the polarity of the head group

Decrease - With temperature, pH and the addition of electrolytes

30
Q

What is a linctus?

A

Viscous preperations where the drug is dissolved in a high % of sucrose and other sweetening agents

31
Q

In what conditions must drugs be stable at during testing?

A

40 degrees C 75% humidity

32
Q

What is a cyclodextrin?

A

These are starches that are modified by enzymes to form a ring It has a hydrophillic outer, and non-polar inside…allowing a non-polar drug to enter

33
Q

Define ‘Enantiomorphism’ and ‘Enantiotropic’

A

Enantiomorphism - When a mixture of D and L molecules are formed from crystallisation Enantiotropic - This is a polymorphic form that can change shape when heated (without going through the liquid/gas states first

34
Q

What is a phase inversion?

A

When an emulsion moves from an o/w –> w/o

Or visa versa

35
Q

What type are all oral and IV emulsions?

A

o/w

As you wouldnt want to drink oil!!

36
Q

What is a crystals habit?

A

Its external shape

37
Q

Define ‘Solubility’

A

The maximum mass or volume of a solute that will dissolve in a given mass or volume of solvent

38
Q

What is the cloud point and kraft point?

A

Cloud Point - The point at which micelles become less water soluble, becoming larger micelles –> becoming cloudy This is for non-ionic surfactants

Kraft Point - The temperature at which the solubility becomes equal to the CMC

39
Q

Explain what the pH partition hypothesis is?

A

When a drug accumulates on a side of the membrane in which the pH is favourable towards ionization. This is because ionized molecules are less likely to be able to undergo membrane transport

40
Q

Define ‘Surfactant/Surface-active agent’

A

They reduce the surface tension at an interface whilst remaining at a low concentration

41
Q

What is creaming, in context of pharmaceutical emulsions?

How would you reduce this?

A

When there is either sedimentation or elevation of droplets in the container, forming a concentrated part at either the top or the bottom of the container

Occurs due to differences in density between the water and oil phases

Rate of this is determined by the stokes equation, so we could reduce the rate by increasing viscosity, and reducing the particle size

42
Q

What is the difference between sugar coating and film coating?

A

Sugar Coating - A core is used and a subcoat

Film Coating - Spraying of a thin film polymer around the tablet

43
Q

Explain the primary minimum, maximum and secondary minimum

A

Primary Minimum - Where there is little repulsive forces, and great attractive forces…so the particles are close together and coagulate Primary Maximum - Due to an increased energy input, the repulsive forces dominate, so the particles are well seperated Secondary Minimum - There is a good inbetween, between repulsive and attractive forces, so the particles are flocculated (can be redispered with shaking)

44
Q

What are the 3 vital properties that are needed for a particulate system to be made into a tablet?

A

Particles must be sufficiently free flowing

When subjected to force, the particles cohere to form a compact of adequete strength

Adhesion of the tablet must not occur

45
Q

What is caking?

A

When particles that fall to the bottom of the container become compressed by particles above. This causes permanent interactions at the primary minimum (coagulation)

46
Q

Are antioxidants needed for pharmaceutical emulsions?

A

Yes

Needed for all bottled things

47
Q

When are suspensions needed?

A

When the drug is insoluble in the vehicle

48
Q

What is a zeta potential? And what does this cause in relation to suspensions? And how can this effect be reduced?

A

The degree of electric charge of particles relative to the medium that surronds them. This causes seperate drug molecules to repel each other By the addition of electrolytes

49
Q

What are the 2 types of multi-particulate?

A

Extruded/Spheronized granulates

Nonpareils - Eg, hundreds and thousands

50
Q

Explain the trade off between surfactant carbon chain length, and solubility/CMC change

A

The greater the lipophillic chain part of the surfactant (micelle) the more drug that it can accomodate

However the larger it is, the lower its CMC and the less soluble it is

51
Q

What is Lundelius rule?

A

Any factor that tends to decrease solubility of a surfactant, will promote surface activity

Eg, a longer carbon chain will decrease its solubility, and make it absorbing to the surface more likely (instead of staying in a micelle)

52
Q

What is the HLB scale?

A

Low = Lipophillic

High = Hydrophillic

Of surfactants

53
Q

What form must preservatives be in to be active?

And what problem can this lead to in terms of micelles?

A

Unionised

So they want to be inside of micelles!! This can decrease the real concentration of preservative that is active

54
Q

Why are Hydrophillic Polymers sometimes used in oral suspensions?

A

To coat the particles, preventing aggregation….and stabilising the suspension

This increases viscosity

PA20308 (5 decks)

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