Tablets Flashcards
What is the most frequently used dosage form?
tablets
What are the advantages of tablets?
economical dosage form
easy to prepare
variety of size and shapes
mostly oral but there are other routes of administration
easy to package, ship, dispense
good stability, especially if coated
accurate doses
portable
relatively tasteless, especially if coated
What are the two methods that tablets are prepared?
compressing or molding
What are the most common excipients you will find in a tablet?
binder
disintegrant
lubricants and glidants
coatings
diluents
colorants
flavoring agents
What are compressed tablets? How are they prepared?
tablets formed by compression with no special coating
prepared with machines capable of exerting great pressure in compacting the powdered or granulated material
powders–>compression–>tablets
the basis for many different types of tablets
What is the problem with compressed tablets?
simple powders may have poor flow and compression characteristics
-they require tremendous pressure
What is the solution to the poor flow and compression characteristics of compressed tablets?
modification such as formation of granules which impart both cohesiveness and flow properties
Which substances can undergo direct compression?
granular chemicals with free-flowing and cohesive properties:
-potassium chloride
-microcrystalline cellulose
-compressible starch
What are some issue that can arise with tablets made from compression?
capping
splitting
laminating
due to air entrapment
What is granulation?
the process of particle size enlargement of powdered ingredients (agglomeration)
-wet granulation
-dry granulation
Which method of dry granulation is preferred and why?
roller compaction is preferred due to improved hardness and friability
When are lubricants added during wet granulation?
added at the end to the dry granules
What is the purpose of diluents in tablets?
acts as a vehicle for the drug
increases bulk
improves or maintains uniformity
diluents make up as little as 5% to 80% of the tablet
What are the diluents used in tablets that we have to know?
lactose
dextrose
microcrystalline starch
starch
mannitol
What is often considered the most important ingredient in tablets?
binders
What is the purpose of binders in tablets?
impart cohesiveness to powders, providing necessary bonding
varies from 1-20%
What will happen to your tablet if you have too little binder? What about if you have too much binder?
too little: fragile tablets (fall apart)
too much: excessive hardness (slow disintegration and dissolution and therefore poor bioavailability)
What are the binders used in tablets that we have to know?
starch
gelatin
glucose
polyvinylpyrrolidone
True or false: tablet excipients may often perform more than one function
true
Give examples of tablet excipients performing more than one function.
dextrose, sucrose, and lactose exhibit binding properties
starch and MCC have binding and disintegrant properties
lactose and sucrose impart hardness
starch, kaolin, and dextrose add softness
mannitol, lactose, and sorbitol exhibit cooling effect
What are the three properties of lubricants in tablets?
glidant effect by coating and lubricating particle surfaces
-improves flow properties
provide anti-adhesive effects
-prevents adhesion of materials to punches and dies
act as lubricant between walls of die cavity and tablet
-facilitating tablet ejection
What are the two types of lubricants?
water insoluble: magnesium stearate, stearic acid, talcum
water soluble
Which item is usually added last to tablets?
lubricants
What is the purpose of disintegrants in tablets?
facilitates break-up of tablet after administration
causes tablet to rupture when it contacts GI fluids
facilitates disintegration, dispersion, and dissolution
What is the mechanism of disintegrants?
draws gastric fluids into tablet, causing porosity in the tablet or swelling and finally break up due to hydrostatic pressure
What are the disintegrants used in tablets that we have to know?
starch
celluloses (MCC)
tartaric acid (used for effervescent tablets)
What is the function of coloring agents in tablets?
esthetics
identification
When are sweeteners and flavoring agents required for tablets?
chewable and effervescent tablets
not required for standard compressed tablets
True or false: a tablet can be made if the excipients are not compatible with the rest of the formulation
false
one must ensure that the excipients are compatible with the rest of the formulation
What is the basic mechanical unit for tablet compression?
punch and die
-lower punch
-upper punch
-die
What is the purpose of tablet coatings?
smooth surface
product identification
mask drug taste
improve drug stability (protect against air or humidity)
defined characteristics of drug release
-functional coatings: enteric-coating, controlled/sustained
release
What are the three types of tablet coatings?
film coating
sugar coating
functional coatings
What are the potential problems with sugar coating?
many steps involve tumbling, tablet must be hard enough to withstand it
must mix uniformly or coating goes on unevenly resulting in tablets of different sizes and weights
What is the most common coating?
film coating
What is a film coating?
thin coating of a plastic like material over the compressed tablets
the basic component is cellulose derivatives like HPMC