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Pharmaceutics 2 > Tablets II > Flashcards

Tablets II Flashcards

1
Q

Before tablet compression, is it important to determine what of the granules?

A

Granules that are to compressed into tablets need to be of the correct weight, hardness and size (hard enough to withstand handling and shipping but must disintegrate and/or dissolve in specific time

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2
Q

Describe the kinds of tablet presses

A

Tablet press may be single punch or multi-station rotary press

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3
Q

Describe the process of compression

A

Compression is the process of pressing material to make it more firm and solid
During tableting, compression forces are applied through punch to compact the granule mass
The force pattern is complex but it may be considered as an axial force causing compression and a radial force exerted by the die wall
Frictional force between granule mass and die walls tends to resists consolidation

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4
Q

The tableting process involves what two events?

A
  1. Reduction in bulk volume by elimination of air (compression)
  2. An increase in mechanical strength of the mass due to particle/particle interactions (consolidation). Bonds form during consolidation and on decompression some break due to the elastic properties of the mass. If sufficient bonds remain, a tablet is formed
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5
Q

What happens when we apply force? What happens when we take the force away?

A

We get bonds, such as ion-dipole, H-bonds, dipole-dipole, ion-induced dipoles, dipole-induced dipoles, and dispersion forces.
When we take the force away, some of the bonds will break but if enough stay, we’ll get a solid dose

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6
Q

What are tableting problems due to?

A

Almost all problems are result of poor granulation

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7
Q

What are some tableting problems?

A

Binding or sticking
Picking
Capping

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8
Q

What is binding or sticking? What causes it?

A

Tablets are ejected with difficulty and it is often accompanied by a grunting sound
It’s caused by inadequate or uneven lubrication of the granules, or if granules are too dry or too wet, if the die is dirty or scratched or if the die is worn

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9
Q

What is picking? What causes it?

A

Granule material sticks to the punch faces, leaving the tablet with a pitted surface
Caused by inadequate or uneven lubrication of the granules, if the granules are under-dried or if the punch face is scratched or damaged

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10
Q

What is capping? What causes it?

A

On decompression the top of the tablet becomes detached.
It is caused by worn tooling, if the compression speed is too fast, if there is excess fines, if the punch fits too tightly into die, if there is excessive pressure, if there is insufficient or ineffective binder, if the granules are over-dried, if the crystal habit of the drug changes

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11
Q

What needs to be tested? (Standards and tests)

A 
Uniformity (USP 905)
Disintegration (USP 701)
Dissolution (USP 711)
Friability (USP 1216)
Hardness (Unofficial)
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12
Q

How is uniformity determined?

A

May be determined by weigh variation of:
-tablets are uncoated
-contain more than 50 mg of active drug
-if the active components provides more than 50% of the total weight
If it doesn’t meet these criteria, content uniformity testing must be done (have to check the amount of drug in 20 tablets)

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13
Q

If tablets meet the weight variation criteria, what needs to be done?

A

Weigh 10 tablets and calculate the content of active ingredient in each based on assay results
We assume the tablets are homogeneous for the distribution of drug
All the tablets much contain 85-115% of the labeled amount and the relative standard deviation (RSD) must not exceed 6%

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14
Q

What happens if one of the tablets are outside of the weight variation limits?

A

A further 20 tablets are weighed
Requirements for the test are met if no more than one unit our of 30 is outside the 85-115% range and the RSD of the thirty tested does not exceed 7.8%

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15
Q

How is disintegration determined?

A

We measure the time for the tablet to disintegrate in a specified test fluid at a specified temperature
There are limitations in extrapolating to bioavailability so dissolution testing is usually required

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16
Q

How does the disintegration test work?

A

USP test consists of an apparatus into which six tablets are placed each into a cylindrical tube which is covered at the bottom by a 0.025 square inch (10 mesh) wire screen
Tubes are raised and lowered through a distance of 5.3 to 5.7 cm 29-32 times per minutes
Plastic discs may or may not be required
Disintegration complete when no solid material with a palpable core remains on the mesh
If one or tow tablets fail, a further 12 tablets are tested
The conditions of the test are met if no more than two of the 18 tablets fail

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17
Q

How is dissolution measured?

A

It it the time required for the tablet to dissolve in a specified test fluid at a specified temperature (some correlation to bioavailability)

18
Q

What are the two types of apparatuses used for determining dissolution?

A

Type 1 apparatus consists of a 1000 ml glass vessel,a motor with a shaft and a cylindrical basket made of a metal screen (40 mesh). Mesh must be stainless steel or gold plated
Type 2 apparatus same except that a paddle is used in place of the basket

19
Q

How do the apparatuses for determining dissolution work?

A

Glass vessel is filled with the fluid and held at the specified temperature (usually 37ºC)
A tablet placed into each of the baskets or into the vessel is paddle is used
Rotation speed is specific in the monograph (60-120 rpm) and the time required for dissolution is specified in the monograph
The quantity of drug which must be in solution (Q) within the time period is also specified in the monograph

20
Q

Why do we determine friability?

A

It is used to determine how the tablet will withstand handling and general wear and tear

21
Q

How do we determine friability?

A

We use an apparatus with a revolving drum which drops the tablet a specified distance a specified number of times
Tablets (5-20) are weighed, placed in the apparatus, tested and the re-weighed
Weight loss of more than 0.8% is usually the limit

22
Q

Is friability official?

A

Test is now in the process of becoming an official test (4 numbers in USP is unofficial)

23
Q

What is hardness?

A

A compressional force when applied diametrically to a tablet just fractures it (how much force did it take to break the tablet?)
It also correlates with disintegration and dissolution

24
Q

How is hardness is determined?

A

Units may be in kg or in kN
Usually a tablet on an anvil and the force is transmitted to it by means of a moving plunger
The tablet hardness is assessed to determine the ability of tablet to withstand shocks during handling of shipping

25
Q

Hardness is a function of what?

A

Compression force during pressing, particle density and size, tablet shape and components of the formulation
Established in-house and frequently is used as an in-process assessment of disintegration
Usual minimum hardness for an uncoated tablet is 5 kg

26
Q

What are the three general categories of tablet coating?

A

Sugar coating
Film coating
Compression coating

27
Q

What are the basic processes used for applying coatings?

A

Pan coating
Air suspension coating
(dip coating and compression coating are not as common)

28
Q

Why do we coat tablets?

A

Coatings are used to mask unpleasant odours and tastes, to protect an ingredient from decomposition and to improve product elegance
May also be used to control release rate or at a particular portion of the GI tract

29
Q

Describe sugar coating

A

Sugar coating is an art and techniques are usually a closely guarded secret
Process may take several days although some partly automated systems are faster
Must have good control over humidity, temperature and dust
Variety of coating pans are used and each must be equipped with hot and cold air inputs and an exhaust system

30
Q

What is required for sugar coating?

A

The compressed tablet cores must have an optimal convexity and be quite hard since they have to withstand he abrasive effect of continuous rolling in a coating pan
The finished tablet must still have the appropriate disintegration/dissolution properties and USP monographs provide specific details for conducting these tests for coated tablets

31
Q

What are the processes involved in sugar coating?

A 
Sealing
Subcoating
Syruping
Finishing
Polishing
32
Q

Tablet cores represent about how much of the finished weight?

A

Only about 50%

33
Q

How is film coating accomplished?

A

Accomplished by deposition of one or more film forming polymers on the surface of the tablet

34
Q

How much of the weight does the film coating represent?

A

Usually the film coating represents less than 5% of the finished tablet weight

35
Q

Why do we use a film coating?

A

Coating may be enteric or non-enteric in nature

36
Q

What are the qualities that film coating should have?

A

Soluble in solvent suitable for process
Soluble in GI fluids
Form a strong continuous film which is smooth and elegant
Stable to heat, light, air, moisture and drug int he product
Have no appreciable taste, odour or colour
Able to support pigment or coating additives
Non-toxic
Crack resistant (usually by inclusion of additives)

37
Q

What are non-enteric coating materials? What about enteric coating?

A

Usually cellulose derivatives while enteric materials are usually phthalate esters of cellulose
Often a plasticizer is included to prevent the film from chipping

38
Q

What are common solvents used for film coatings?

A

Alcohols, esters, chlorinated hydrocarbons, acetone, and other ketones

39
Q

What are aqueous-based coating for?

A

Recently, aqueous-based coatings have been developed due to concerns regarding environment, safety and toxicity

40
Q

What is compression coating? Why do we use them?

A

Core is placed in the centre of a large die and surrounded with coating material in the form of free flowing granules which is compressed into a final product
Incompatible drugs may be formulated this way
May also be used for repeat-action tablets where first dose in the coating and a second dose in much slower disintegration core
Layered or lamintated tablets are also common for these purposes

Pharmaceutics 2 (8 decks)

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