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
What are the processes for film coating?
coating pan
spray in a fluidized stream
press coating
Describe pan coating.
mixing of tablet mass:
-pan shape, rotational speed and loading affect the mixing of
tablets and coating
-uniform mixing is essential to deposit the same quantity of
film on each tablet, poor tablet movement causes errors
Describe press coating.
compaction of a dry coat around a tablet core, produced on the same tableting machine
avoids the use of solvents
can be used to separate incompatible drugs in the same tablet, making a layered tablet
What are the challenges of aqueous film coating process?
slow evaporation of water
orange peel effect
covering of score line
disfiguration of the core tablet
Why is the organic film process not preferred?
expensive and sometimes not environmentally friendly
What is enteric coating?
allows for disintegration in the intestine rather than the stomach
does not dissolve in the acidic pH of the stomach
protects drug from acid hydrolysis
What is functional coating?
allows for timed release
-can have particles coated with varying thicknesses of coating
so drug is released gradually from the dosage unit
What are molded tablets?
prepared by molding rather than compression
soft, soluble, and designed for rapid dissolution
Which excipients will you not find in molded tablets?
disintegrants
lubricants
coating
When are molded tablets not appropriate?
potent drugs
-due to difficulties with content uniformity
What are the most common diluents found in molded tablets?
mannitol
lactose
dextrose
What are chewable tablets? Who are they intended for?
tablets intended to disintegrate in the mouth
primarily intended for children who prefer chewing a flavoured medication rather than swallowing
What are the advantages of chewable tablets?
pleasant taste
no bitter or unpleasant aftertaste
convenience and patient acceptance (esp kids and geriatrics)
rapid onset of bioactivity (no disintegration)
What are the disadvantages of chewable tablets?
limitations on # of drugs that can be put in
drug material is bitter and flavouring is difficult
What is a widely used excipient in chewable tablets? Why is it so widely used in chewable tablets?
mannitol
-70% sweetness compared to sucrose
-cool taste and mouth-feel
-non-hygroscopic
Which excipient is commonly used in chewable tablets when you want the tablet to be sugar free?
xylitol
Why is color added to chewable tabblets?
appeal of the tablet
correlate with flavour
Which excipient is not required in chewable tablets?
disintegrants
What is an important counselling point in regards to chewable tablets?
do not swallow whole, chew to break the tablet
Which anticonvulsant is commonly found as a chewable tablet for kids?
carbamazepine
What are effervescent tablets?
large wafer-like tablets which dissolve rapidly in water
large surface area allows for faster rate of solution
What facilitates the breakup of effervescent tablets?
release of CO2 generated from sodium bicarbonate and citric or tartaric acid
chemical rxn is initiated when tablet is placed in water; water solubilizes the reagents so reaction can take place
What are important considerations to keep in mind with effervescent tablets?
binders, fillers, and lubricants are water soluble
moisture excluded during manufacturing
package in moisture-proof containers to avoid degradation
flavoured & sweetened
What are important counselling points for effervescent tablets?
dissolve in water at room temperature
once effervescence stops, wait >5 min and stir solution for about 10s and then drink
store away from humid conditions
What is the difference between sublingual and buccal tablets?
sublingual: placed under tongue
buccal: between cheek and gum
What are sublingual and buccal tablets designed to produce?
designed to produce immediate systemic effect by enabling drug to be directly absorbed through the oral mucosa
Which excipient do sublingual and buccal tablets not have?
disintegrant
What is the physical design of sublingual and buccal tablets?
small
soft
flat
may be molded or compressed (lightly)
In terms of dissolving, what is the difference between sublingual and buccal tablets?
sublingual: dissolve promptly to provide rapid effects
buccal: erode relatively slowly
What are ODTs?
solid dosage form which disintegrates rapidly, usually within a matter of seconds, when placed on tongue
How are ODTs different from sublingual and buccal tablets?
ODTs dissolve in seconds, may not result in faster therapeutic onset
sublingual and buccal require more than a minute to dissolve
What are other names used for ODTs?
oro-disperse
mouth dissolving
quick-dissolve
fast-melt
freeze-dried wafers
What are the advantages of ODTs?
enhance clinical effects through pre-gastric absorption
increases bioavailability
What must always be added to ODTs?
flavours and sweeteners
What are important counselling points with ODTs?
do not administer with wet hands
store in dry place
may cause burning or tingling on tongue
What are the major challenges associated with sublingual, buccal, and ODTs?
drug loading (only good for small doses)
taste masking and palatability (shouldnt be gritty)
friability (balance between soft and hard)
extra cost of packaging (require individual blistering)
What are lozenges designed to do?
promote saliva flow, which is soothing
may be used for systemic effect if the drug is well absorbed through the buccal lining
they contain one or more medications, usually sweetened
Who are lozenges good for?
patients who have difficulty swallowing
-pediatrics
-geriatrics
-patients with GI blockage
Who are lozenges a potential danger to?
kids
they look and taste like candy
What are some drugs in lozenge form?
fentanyl
nicotine
sore throat
flurbiprofen
zinc
How are lozenges prepared?
molding (gelatin, fused sucrose or sorbitol base) OR compression of sugar-based tablets
Molded lozenges are sometimes referred to as ____, harder lozenges are sometimes referred to as ___.
pastilles
troches
What are the basic properties of a good lozenge?
slow uniform dissolution or erosion over 5-10 minute period
smooth surface texture
pleasant flavour masking drug taste
Which excipient will you find in a hard lozenge, soft lozenge, and chewable lozenge?
hard lozenge: sucrose
soft lozenge: polyethylene glycol
chewable lozenge: gelatin
What is the composition of hard lozenges?
solid syrups or sugars
-typically 55-65% sucrose and about 35-45% corn syrup
-needs a low moisture content (0.5-1.5%)
How are hard lozenges made?
heating sugars and other ingredients together and then pouring the mixture into a mold
-the molds can shape the mixture to look like a sucker/lollipop
How are soft lozenges made?
can be hand rolled and then cut into pieces (because of soft texture)
more convenient: pour the warm mass into a plastic troche mold
What is the typical composition of soft lozenges?
polyethene glycol 1000 or 1450
chocolate
sugar-acacia base
What is the benefit of adding acacia or silica gel to soft lozenges?
acacia: adds texture and smoothness
silica gel: suspending agent to keep materials from settling to the bottom of the mold
If using PEG for a soft lozenge, what should be done during the filling process?
cavitities of the troche mold should be overfilled
before the material has solidified, use the spatula to level and even out the mass
-chocolate does not shrink as it cools so filling is unecessary
Which group of patients are chewable lozenges popular with?
pediatrics
What is the composition of chewable lozenges?
most formulations are based on the glycerinated gelatin suppository formular which consists of glycerin, gelatin, and water
What is the flavour of chewable lozenges?
fruit flavoured
may have a slightly acidic taste to cover the acrid taste of the glycerin
What is the rule of thumb for adding flavouring to lozenges?
prepare the lozenges without any drug present and flavor these blank lozenges to taste
then when drug is added, start with 5-10 times the amount of flavoring used in the blank lozenges
