Tablets 1 Flashcards
1
Q
What is a tablet?
A
A tablet is a dose form of medication containing one or more drugs to which excipients may have been added and compressed as granules or powder to a definite shape
(70-80% of all medications taken are in tablet form)
2
Q
What are the factors that make tablets a good dose form?
A
- Dosing accuracy
- Stability (drugs sold in a solid state are generally more chemically stable- may be coated to protect them from the environment and stomach acid)
- Patient acceptance (conveniently carried, odour or taste can be masked, attractive appearance)
- Diversity (most tablets intended to be swallowed but also sublingual, implant and chewable. Drug release may be immediate or sustained)
3
Q
What are disadvantages to tablets?
A
- solid dose form may cause irritation to the GI mucosa
- may have bioavailability problems since dissolution must occur before drug is available for absorption
4
Q
What attributes must a tablet have?
A
- able to withstand the rotors of mechanical tx during production, packaging, shipping, etc
- must be free of defects - cracks, ships, discolorations
- reasonable chemical and physical stability
- contain the proper amount of medication and release in a predictable and reproducible manner
5
Q
What solubility and permeability properties does a class 1 drug have?
A
- class one drugs have few problems (is both soluble and permeable)
6
Q
What solubility and permeability properties does a class 2 drug have?
A
- class two drugs - the rate limiting step for bioavailability is solubility/ dissolution
7
Q
What are the solubility and permeability properties of class 3 drugs?
A
- class 3 drugs - the rate limiting step for bioavailability is crossing the biological membranes
8
Q
What are the solubility and permeability properties of class 4 drugs?
A
- class 4 drugs present a problem- are not very efficient at crossing biological membranes or dissolving
9
Q
What are the properties of granulation?
A
- materials intended for compression into a tablet must have 2 essential characteristics: fluidity and compressibility
10
Q
Why is fluidity necessary?
A
- fluidity is necessary for the transport of the material through a hooper into a feeder frame or a die cavity
11
Q
What is compressibility?
A
- the property of forming a stable compact when pressure is applied
12
Q
Do powders flow freely?
A
- no, powders do not usually flow freely - the hopper may become plugged by bridging or may rat hole
13
Q
What can poor flow properties lead to?
A
- poor flow properties can lead to variation in tablet weight, content and hardness
14
Q
What attributes should good granulation have?
A
- good granulation should approach spherical shape (minimizes inter particle friction and static)
- should present a NARROW range of particle sizes (uniform full and bridging between particles when compressed)
- should have homogenous distribution of all materials (should have content uniformity)
- should have acceptable compression properties (tablet hard enough to remain intact yet able to disintegrate when taken)
15
Q
What generally needs to be added to confer appropriate properties of granules?
A
- additives and excipients
16
Q
What specifically does the additives or excipients aid in?
A
- aid in granule formation and flow, compression and disintegration and dissolution
17
Q
What is a diluent (filler) used for with tablets?
A
- must be used to give the product adequate bulk- some potent drugs may have the dose in the microgram range
18
Q
What excipients do diluents cover?
A
- lactose
- sucrose
- mannitol
- sorbitol
- calcium sulfate
- calcium phosphates
- starch
- microcrystalline cellulose
19
Q
What are some of the properties of lactose?
A
- common diluent
- inexpensive, readily soluble and reasonably inert
- crystals tend to be plastic and deform under pressure - so good compressibility properties
- no hydroscopic
- prone to browning with some drugs and may lose compression characteristics with some drugs
20
Q
What are some of the properties of sucrose?
A
- often used to impart hardness to tablets but used in small amounts since it is somewhat hydroscopic
- tablets containing sucrose tend to harden with time
- subject to browning with some drugs
21
Q
What are some of the properties of mannitol?
A
- inert and non-hydroscopic
- used in chewable tablets because of mouth-feel properties (cool, smooth, slightly sweet)
22
Q
What are some of the properties of calcium sulfate?
A
- low solubility and non-hydroscopic
- inexpensive and useful for acidic, neutral and basic drugs
- good adsorption of oils
- inert but combined with sugars it tends to harden over time
23
Q
What are some of the properties of microcrystalline cellulose?
A
- insoluble, inert-free flowing filler which can also function as a binder and a disintegrant
- widely used in direct compression
- may be added dry to granules to improve binding, but is relatively expensive
24
Q
What is the function of binders?
A
- hold together powders by adding cohesive forces to the diluent and are used as needed
- used with care since the tablet must disintegrate at some point
- usually sugars or polymers are added as solutions or slurries to powdered material
25
What are some examples of binders?
- starch
- pregelatinized starch
- gelatin
- polyvinylpyrolidone
- methylcellulose
- ethylcellulose
- polyvinyl alcohols
26
What are some of the properties of starch?
- most common binder
- neutral and non-reactive
- also functions as a disintegrating agent
- may give soft granules so additional excipients may be required
27
What are some of the properties of starch?
- stronger binder than starch
| - use largely replaced by synthetic polymers
28
What are some of the properties of natural gums?
- acacia and tragacanth are still used but are widely being replaced by synthetic polymers
- bacterial contaminants are a problem
29
What are some of the properties of polyvinylpyrrolidone (PVP)?
- popular and a very useful binder
- slightly hydroscopic
- able to use alcoholic or hydro-alcoholic solvents
30
What are some of the properties of cellulose derivatives?
- good binding properties and are very versatile
- some are alcohol soluble
- most common are methylcelllose, carboxymethylcellulose, ethyl cellulose and hydroxypropylmethylcellulose
31
What is the function of a lubricant as an excipient?
- used to ease the ejection of the tablet from the die, to prevent sticking to the faces of the punches and to reduce wear on the tooling
- applied to coat granules therefore particle size of the lubricant is important since we want uniform coating
- may be water soluble or water insoluble depending on product requirements
- magnesium stearate is widely used
- slightly alkaline- can cause problems and tend to waterproof granules which may affect disintegration/dissolution properties of the tablet
32
What are some examples of the products used as lubricants?
- magnesium stearate
- calcium stearate
- zinc stearate
- sodium benzoate
- light mineral oil
- polyoxyethylene monostearate
- magnesium lauryl sulfate
- talc
- polyethylene glycol
- hydrogenated vegetable oils
- sodium lauryl sulfate
33
What are some examples of disintegrates? (see concentrations on slide 26)
- substance added to the granulation to cause the tablet to break apart in an aqueous environment
- reverses the effect of the binder and the compression force
- may be external or internal
(external when added to the formed granules, internal when it is a component of the granulation mixture)
- function by swelling or reacting with water to cause disruptive forces
34
What are uses/properties of colorants? (see examples on side 29)
- usually added to tablet formulation to increase elegance or for identification
- pastel shades often used since these are least likely to slow mottling
- frequently used as lakes since these are less likely to bleed and have better uniformity
- some dyes are photosensitive and may discolor is not protected from the light
35
What is the most important step in tableting?
granulation
36
What are the different processes for producing granules?
- dry granulation
- wet granulation
- no granulation (direct compression)
37
What are the steps of wet granulation?
1. milling of the drug and excipients
2. mixing of the milled powders
3. preparation of a binder
4. preparation of wet mass
5. screening of wet mass
6. drying of granules
7. screening dry granules
8. mixing with lubricant
9. tablet compression
38
What are the steps of dry granulation?
1. milling of the drug and excipients
2. mixing of milled powders
4. compression into slugs
4. screening of slugs
5. mixing with lubricant
6. tablet compression
39
What are the steps of direct compression?
1. milling of drug and excipient
2. mixing of milled powder
3. tablet compression
