Tablets Flashcards
Tablets normally contain excipients in addition to the active ingredients. TRUE OR FALSE?
TRUE
Tablets are mainly used for systemic delivery. TRUE OR FALSE?
TRUE
Drug must dissolve first before being absorbed - needs to disintergrate/ needs to dissolve (dissolution). TRUE OR FALSE?
TRUE
How can tablets be adninistered?
- Swallowing whole
- After being chewed
- Retaining in the mouth - avoids acidic environments int he stomach
- Buccal (designed to release drug slowly)
- Sublingual (designed for fast action)
- Dissolve or disperse in water before admin
What are some of the disads for tablets as dosage form?
- Poor bioavailability of poorly water soluble drugs
- difficult to swallow for some patients
- Iriitation to the GI tract (some drugs)
What are some general attricbutes for a good tablet?
- Correct dose
- Elegant weight an dsize are consitent
- Drug should be released in a controlled way
- Biocompatible - non toxic excipients
- Sufficient mechanical strength to survive transport and handling
- Physically, chemically and biologically stable
- Properly packed
How are tablets formed?
-By forcing particles into close proximity to each other by powder compaction so that the particles cohere into a porous solid of defined shape
What is powder compaction?
The formation of a porous specimen of defined geometry by powder compression
What is powder compression?
-Reduction of volume of a pwder due to the application of a force
Describe the three stages of tablet formation?
- The filling stage - powder fills teh die by gravoty or centrifugal force
- The compression stage - The upper punch lowers into the die and the powder is compressed, then the upper punch moves up
- The ejection stage - the lower punch moves up to reject the tablet
Describe the single punch tablet press?
- One die and one pair of punches
- The hopper shoe moves to and from the die by translational or rotational movement
- Tablet weight
- Lower punch remains stationary during compaction
- About 200 tablets per minute
Describe the rotary tablet presses?
- Many dies on the die table and many pairs of punches
- Die table and punches rotate together
- The same punches always works with the same die
- 10000 tablets per min can be made
- Suitable for mass production
What are the reasons for granulation for tableting?
- To improve flowability of the powder
- To improve mixing homogeneity and reduce segregation
- To improve the compactability of the powder (e.g addition of binder)
- To improve density of powder
- To ensure a homorgeneous colour of the tablets
- To improve dissolution or poorly soluble drugs by dispersing fine powdes of the drug in hydrophilic diluent
Describe the process of tableting via wet granulation?
- Dry powder mixing -disintergrant can slo be included in this step
- Wet granulation
- Dry granules
- Dry granules of controlled particle sizes
- Tableting
What are the disads of tablet production via wet granulation?
- Production time is long
- Consumes energy in the drying process in wet granulation
- Stability problems - some drugs are not stable in wet conditions
- High costs
What are the adavantages for tablet production by direct compaction?
- Simplified production procedure -only two steps
- Reduced production time
- Reduced consumption of energy
- Low cost due to reduced consumption of energy and time
- Less stability issues
- Potentially faster dissolution
What are the disads for tablet production by direct compaction?
- Need special grades for excipients
- Higher risk powder segregation
- Powders of high drug content is difficult to form into tablet if the drug has poor compactability
What two types of drugs is direct compaction used for?
- Drugs that have good flowabiltiy (e.g powders with large size)
- Potent drugs that are of low content (in this case the powder properties are controlled by excipients
List some type of tablet excipients
- Diluent (bulking agent)
- Disintegrant
- Binding agent
- Glidant (improves the flow of powders)
- Lubricant (reduces friction between powder and die)
- Antiadherent
- Sorbent
What are the ideal features for an ideal diluent?
- Biocompactible
- Chemically inert
- Non-hygroscopic
- Low cost
- Good compressibility and compactibility
- Acceptable taste
Describe lactose as a diluent ?
- dissolves readily/most commonly used filler in tablets/pleasant taste/available as anhydrous and crystalline/anhydrous lactose possesses excellent compaction properties
What are the disads for using lactose as a diluent?
- Intolerant to some people
- Anhydrous lactose may spontaneously convert to the more stable crystalline form
Describe celluose powder as a dileunt and its disads?
- Biocompactible
- inert
- Good disintegrating properties
- Good compactibility
Disads
-Hygroscopic
What is the purpose for disintegrants?
-added to formulation to ensure that tablets break up to small particles when in contact with liquid
What si the mechanism of which disintegrants work?
- Facilitates water uptake (helping to transport water into the pores)
- Cappilary forces suck water into the tablets
- Rupture the tablets by swelling of the disintegrant
- deformed particles restore to their original shape upon contact with water
- Particles repulsion upon contact with water
- Production of CO2 (for effervescent tablets)
Name a few disintegrants?
- Starch (potato,corn,maize)
- Cellulose
- Modified starch or modified cellulose
- Gas generating disintegrant (bicarbonates/CO2 is produced in contact with water
Why are binder added?
-To ensure that tablets can be formed with require mechanical strength
Binder can be added as -Dry powder before wet granulation -Solution to produce wet granules -A dry powder which is mixed with other powder before compaction. TRUE OR FALSE?
TRUE
What type of binders are the best and provide examples?
Solution binders
e.g sucrose, starch, cellulose derivatives
Provide examples of dry binders ?
-Microcrystalline cellulose and crosslinked pvp
Why are glidants added?
-To improve the flowability of the granules/powders
What type of glidant is mostly used?
- Colloidal silica (very small particles)
- It is used in small quantities
How do glidants improve flowability?
-By adhering to the surface of other particles and reducing interparticulate friction
Magensium stearate cannot improve powder flow. TRUE OR FALSE?
FALSE
Why are lubricants used?
To ensure low friction between tablets and die wall
What does high friction result in?
- Vertical scratches on the tablet edges
- Capping or fragmentation of tablets during ejection process
Describe the mechanism of lubrication
- Fluid lubrication -rarely used
- Boundary lubrication - fine particulate solid e.g magnseiium stearate - most widely used
Lubricants can reduce tablet strength as lubricants reduce bonding between particles. TRUE OR FALSE?
TRUE
The dissolution of tablets may be retarded by lubricants as most of lubricants are hydrophobic. TRUE OR FALSE?
TRUE
The more the lubricant the stronger the retardation effect. TRUE OR FALSE?
TRUE
The sequence and manner that the lubricant is mixed with the powders may also affect the dissolution of drugs. TRUE OR FALSE?
TRUE
Antiadherent reduce the adhesion between the powder and the punches and give an example. TRUE OR FALSE?
TRUE
e.g magnesium stearate
What are sorbents?
-Substances that are capable of absorbing some quantities of liquid and appears to be dry powder
What are the some of the technical problems during tableting?
- High dose and weigth variation of the tablets
- Low mechanical strength of the tablets
- Capping and lamination of the tablets
- Adhesion or sticking of powder to punches
- High friction during tablet ejection
What properties must be controlled to avoid technical problems during tableting?
- Powder properties
- Homogeneity and segregation tendency
- Flowability
- Compression properties and compactability
- Friction and adhesion properties
Affter interparticle spaces are reduced to the minimum, any further increase of pressure will result in the deformation of particles. TRUE OR FALSE?
TRUE
What is elastic and plastic deformation ?
Elastic - Temporary deformation due to small movement of the cluster of molecules or ions
Plastic - permanent deformation due to the sliding of molecules along sliding planes within the particle
Elastic and plastic deformation can be time-dependent or time independent. TRUE OR FALSE?
TRUE
If stress is applied for a long time elastic deformation can become plastic deformation. TRUE OR FALSE?
TRUE
What is the force displacement profile?
- It is the relationship between upper punch force and displacement
What are the mechanisms of bonding in tablets?
- Bonding by intermolecular forces
- The formation of solid bridge
- Mechanical interlocking
- binder bridges
Tablets usually fail by breakage of interparticle bonds or by interparticle breakage. TRUE OR FALSE?
TRUE
What factors cause lamination and capping?
- Formulation factors (granules are too elastic in nature/bonding failure)
- Compaction factors (the force of compression is too large/rate of force application too fast/the ratio between initial compression to main compression is too large/the condition of the die cavity)
What reasons cause tablet strength to be reduced?
- Bonding due to water condensation
- Change of microstructure due to dissolution of materials in condensed water
- Softening of amorphous materials due to the moisture
What factors may cause tablet strength to increase?
- Crystallisation of materials dissolved
- Crystallisation of amorphous materials in rubbery state
- Restructure of amorphous materials due to moisture uptake
- Change of tablet microstructure due to polymorphic transformations
What are the three different tablet types?
- immediate release tablets
- Extended release tablets
- Delayed release tablets
List the different types of tablets
- Chewable tablets
- Efferverscent
- Lozenges
- Sublingual
- Buccal
What are the different ways tablets can be tested?
- Tablet weight
- Dose uniformity
- Disintergration
- Dissolution
- Mechanical strength (friability)
What are the different ways tablets can be coated
- Sugar coating
- Film coating
- Press coating
What are the reasons for tabelt coating?
- protects the ingredients from light and mositure
- Masks bitter taste
- Coloured caoting hides batch to batch difference
- Appearance and sales appeal
- Coating increases physical strentgh of the tablet and makes it easier for automatic packing
- Functional filsm for enetric or controlled release properties
What is sugar coating?
-Sealing of tablet cores by a polymer layer to prevent the moisture from getting into the tablets
How is film coating achieved?
-By spraying of coating liquid on to tablets, a thin film of polymer is formed when the solvent is removed
The film in film coating is thin enough to preserve the original shape of the tablets and to reveal the monograms embossed in the tablets during the compression. TRUE OR FALSE?
TRUE
Film coating an be automatically controlled. TRUE OR FALSE?
TRUE
What does coating liquid usually contains?
- A polymer which forms the main structure of the film
- A plasticizer which reduces the brittleness of the film
- Colourants, pigments
- Solvent
What is press coating?
-Compaction of granular materials arounf an already preformed core, mainly to seperate chemically incompatible maetrials
An inert middle layer can be added to seperate the layers that are not compatible in press coating. true or false?
TRUE
Why enetic coating?
- Protect drug
- Protect drug from stomach acid
What materials are used for enteric coating?
-The materials usually have a carboxylic group s on the polymer and their solubilities are pH sensitive e.g cellulose acetate
