Gastroenterology > Tablets > Flashcards

Tablets Flashcards

(81 cards)

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1
Q

Advantages of tablets

A

Mass production, dry dosage form increases stability, convenient transport, easy to dispense, good uniformity of dosing, can coat and mask taste, versatile drug delivery

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2
Q

Moulded tablets

A

Prepared by moulding, soft and soluble, rapid dissolution

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3
Q

Compressed tablets

A

Prepared by compression, hard, can be coated

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4
Q

Types of tablets

A

Sugar coated, film coated, enteric coated, chewable, effervescent, buccal + sublingual, vaginal + rectal

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5
Q

Common ingredients of tablets

A

Active drug, filler/diluent, binder, disintegrant, lubricant, glidant

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6
Q

Filler/diluent

A

Add necessary bulk to the formulation for handling and processing

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7
Q

Binder

A

Promote adhesion, maintain integrity of tablet

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8
Q

Disintegrant

A

Facilitate breakup of tablet for absorption

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9
Q

Lubricant

A

Aid ejection of tablet from die cavity after compression

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10
Q

Glidant

A

Enhance powder flow through machinery

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11
Q

How does adsorption of drug on surface of excipient effect the drug

A

Decreased particle size, increased surface area of drug, increase F

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12
Q

How does a rotary press work for tablet compression

A

Head carrying sets of punches and dies revolves continuously, granules run out of hopper into feed frame, upper and lower punches move between pair of rollers, after compression lower punch lifts to eject tablet

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13
Q

What is granulation

A

Primary powder particles made to adhere to form multi particle entities

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14
Q

What are the ideal characteristics of granules

A

Spherical shape, smaller particle size distribution, adequate moisture, good compressibility, sufficient hardness

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15
Q

Why granulate?

A

Prevent segregation, improve content uniformity, improve flow properties of mix, improve compaction, reduce hazards of toxic material, reduce caking of hygroscopic material

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16
Q

What is the most commonly used filler/diluent and why

A

Lactose, inexpensive, number of forms, freely but slowly soluble in water

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17
Q

Wet granulation production techniques

A

Oscillating granulation, high speed mixers/granulators, fluid bed granulation, extrusion-spheronisation

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18
Q

Stages involved in particle-particle interactions during wet granulation

A

Particle-particle interactions by forming liquid bridges, particle-particle interactions by forming solid bridges

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19
Q

Advantages of wet granulation

A

Reduced material segregation during storage, useful for manufacture of tablets with low drug concentration, use conventional excipients, amenable to post processing unit operations eg coating

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20
Q

Disadvantages of wet granulation

A

Several steps required, may produce hydrate forms of drug, solvents used need to consider drug degradation, drug can crystallise out during drying if soluble in granulating fluid causing polymorphism, need heat for drying

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21
Q

Common granule tests

A

Loss on drying (moisture content), bulk density, particle size distribution, angle of repose (flowability)

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22
Q

Why is moisture content important?

A

Affects flow of material, affects compressional characteristics (crystal hydrates often compress better), final water content affects stability, quality and strength

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23
Q

Commonly used methods to dry granules

A

Tray drying, fluid bed drying, vacuum drying, microwave drying

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24
Q

Convective heat transfer

A

Uses moving medium (air)

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24
Conductive heat transfer
Wet solid in contact with hot surface, bulk of heat transfer by conduction
25
Heat transfer by radiation
No transfer medium needs to be present
26
What sort of heat transfer does tray drying use
Mainly convection
27
What is tray drying
Granules dried in drying oven on trays
28
Disadvantages of tray drying
Time consuming, labour intensive, evaporation from surface (solvent has to move up through bed- solute migration), granules may aggregate due to bridge formation, may need to re-sieve/remix
29
How does fluid bed drying work
Dynamic convective dryer, drying gas forced through a solids bed and granules are suspended, particles continually lifted by drag and fall down under gravity
30
What are the advantages of fluid bed drying
Short drying time, high product output, drying occurs at constant rate, temperature uniform and easily controlled, turbulence produces attrition which makes round free flowing particles, reduces problems of particle aggregation, reduces risk of soluble material migrating, can be mobile
31
What are the disadvantages of fluidised bed drying
Turbulence may cause excessive attrition, vigorous particle movement in hot dry air can generate static electricity and cause explosion, fine particles may become entrained in fluidised air
32
How does vacuum oven drying work
Wet granules are contact with a hot surface, bulk of heat transfer is by conduction
33
How does microwave drying work
Microwaves fall on small polar molecules, electrons attempt to resonate in sympathy with radiation, molecular friction thus heat generation
34
Advantages of microwave drying
Rapid drying at fairly low temps, bed stationary- avoids dust and attrition, solute migration reduced (uniform heating of wet mass)
35
Disadvantages of microwave drying
Batch smaller than fluidised bed, care must be taken for radiation exposure of operators
36
What is solute migration
Solvent moves toward surface of solid and takes dissolved solute with it
37
What does solute migration cause
Local variability in concentration of soluble drug and excipients in dried product
38
Intergranular migration
Solutes move from granule to granule causing gross maldistribution of drug, tablets may have excess or deficiency of drug
39
Intragranular migration
Solutes move to periphery of each granule
40
Consequences of solute migration
Loss of active drug, mottling of coloured tablets, migration of soluble binders
41
Factors influencing solute migration
Nature of substrate, viscosity of granulating fluid, drying method, initial moisture content
42
How do we minimise solute migration
Use minimum quantity of granulating fluid, ensure fluid well distributed, prepare smallest granules that flow easily, avoid tray drying (if unavoidable remix dry granules before compression)
43
What do we do if dried product coheres into large mass after wet granulation
Pass through sieve to break up into relatively uniform sized granules
44
What excipients are commonly added before compression in wet granulation
Glidant, disintegrant, lubricant
45
What can inadequate lubrication cause
Scratches on tablets or matte dimpled finish
46
How are lubricants most effective
When dispersed over surface of particles in complete layer
47
Deleterious effects of lubrication
Hydrophobic (water repellant), slow disintegration/dissolution, reduce interparticulate bonding
48
MOA of disintegrants
Swell in contact with water, provide network of hydrophilic pathways
49
What are the 2 methods of dry granulation
Slugging and roller compaction
50
What is the process of slugging
Mixed powders compressed into oversized tablet using tablet press then milled to produce granules of required size
51
What is the process of roller compaction
Mixed powders compressed using roller compactor then size reduction
52
Advantages of dry granulation
Use conventional grades of excipients, usually not see change in drug morphology due to processing, no solvent required and no heat required
53
Disadvantages of dry granulation
Specialised equipment, segregation of components may occur post mixing, need powders with cohesive properties, tablets produced by dry granulation tend to be softer than those produced by wet granulation
54
What is direct compression
Add all tablet components together, mix then compress
55
Advantages of direct compression
Save time and cost, eliminates heat and moisture
56
Disadvantages of direct compression
Powder flow issues, specialised, more expensive, tablets tend to be softer, if drug loading high compression affected by compression properties of drug
57
What excipients do chewable tablets not have
Generally no disintegrants, must chew thoroughly and not swallow whole
58
Commonly used sweetening agent for chewable tablets
Mannitol
59
What is the benefit of xylitol as a sweetener
Sugar free, sweeter than mannitol, desirable mouth feel
60
Uniformity of content test
Assay of active drug in a number of single dose units to see if individual contents are within set limits
61
Uniformity of weight test
Weigh 20 units taken at random and determine average mass
62
Disintegration test
Determine whether tablets disintegrate within prescribed time when put in liquid medium under experimental conditions
63
Dissolution test
Determine the release of drug from the tablets measure vs time
64
Friability test
Determine weight of tablet when subjected to abrasion and shock
65
Hardness test
Determine crushing force required to break tablet along its diameter
66
Advantages of scored tablets
Dose flexibility, decreased cost (less formulations)
67
Disadvantages of scored tablets
Difficulty breaking, uneven breaking, loss of mass
68
How do we overcome breaking problems with scored tablets
Use tablet splitter, break in pharmacy, manufacturer change shape or formulation
69
Elastic behaviour
Add load to end, stretch, remove load, return to normal
70
Plastic behaviour
Too much load get to elastic limit, remove stress, doesn't return to normal, plastic deformation
71
Tabletability
Capacity of powdered material to be transformed into tablet of specified strength under effect of compaction pressure
72
Compressability
Ability of material to undergo a reduction in volume as a result of applied pressure
73
Compactibility
Propensity of powder to form a coherent tablet
74
What are the indices of compactibility
Bonding index and brittle fracture index
75
Bonding index
Estimate survival of tablet strength during decompression
76
What does a high bonding index mean
Large portion of strength is maintained during decompression
77
What does a low bonding index mean
Tablets are more friable
78
Brittle fracture index
Reflect ability of tablet to resist fracturing and lamination during handling
79
Brittle fracture index close to 1
Brittle material
80
Brittle fracture index close to 0
Non-brittle
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