Tablets Flashcards
What is a tablet?
solid preperation which contains a single dose of one or more active ingredient.
Advantages of tablets
-good patient compliance
-convenient
-accurate dosing
-chemical, physical and microbial stability
-cheap, robust, elegent
disadvantages of tablets
-generally systematic delivery
-poor bioavailability
-must be swallowed
-first pass metabolism / GI track instability
-local irritation -GI mucosa
Immediate release tablet types
disintegrating
chewable
effervescent
sublingual / buccal
modified release tablet types
-extended release - released slowly at a constant rate
-pulsatile release - released in two or more pulses
-delayed release - released some time after administration
disintegrating tablets
-Drug release: disintegration>dissolution>absorption
-disintegration rate: dependent on several formulation and production factors
-dissolution rate: limited by drug factors such as solubility and particle size
-absorption rate: lipophilicity
examples: paracetamol, ibuprofen
chewable tablets
-disintegrate in mouth
-mechanical disintegraiton - no disintegrant
-drug dissolves in stomach
-rapid effect, no water requied
-for patients with difficulty swallowing
-flavourings/colourings commonly used
-examples: vitamins, gaviscon
effervescent tablets
-dropped into glass of water
releases co2, fascilitating disintegration and dissolution
rapid drug action
examples: analgesics, vitamins
compressed lozenges
-dissolves in saliva
-slow drug release - no disintegrant
-systematic and local delivery
-filler and binder - water soluble and acceptable taste eg. carbohydrates and sugar
-colouring, flavouring
-high pressure - increased hardness and low porosity
eg. strepslis, nicotine
sublingual and buccal tablets
sublingual - tablet placed under tongue
buccal - tablet placed in =side of cheek
-systematic delivery avoiding first pass metabolism / Gi tract
-rapid drug release - small, porous, completely disintegrate and dissolve
-buccal modified release - slow release (1-2 hours)
eg. nitroglycerin, loratadine, nicotinell
excipients
-ensures the produciton process runs efficiently and produces tablets of a required standard
types of excipients
procceses: direct compression
advantages and disadvantages
mixing > tabletting
advantages:
reduction in manufacture time and costs
faster drug dissolution
disadvantages: specialist fillers/binders required
powder must have good flow properties
powder segregation
poor drug compactability
poor colour uniformity
processes: granulation
advantages and disadvantages
mixing>agglomeration>drying>milling>mixing>tabletting
Advantages:
-improves homogeniety, prevents powder segregation
-improves powder flow properties
-increases compactability
-increases bulk density
-colour homogeniety
diadvantages:
-increase in production time/costs
may cause drug hydrolysis
compaction
forcing particles into close proximity to eachother by confined compression.
single punch tablet press
output upto 200 tablets/min - production of small batches
eg. during formulation development and clinical trials
rotary tablet press
> 10,000 tablets/min
multiple sets of tooling
powder flows by gravity from the hopper onto the die table and feed into the die by powder feeder, punches compress powder and feeder knocks tablet to eject
technical problems during tabletting
weight/dose variations
low mechanical strength
capping
lamination
sticking - powder stinks to surface of punch
picking - particles stick to letts/logos of the punch
chipping
Reasons for tablet coating
-protect the dryg
-mask the taste
-ease of swallowing
-improve appearance
-rapid identification
-ease of handling
-increase bulk
-modified release characteristics
3 types of tablet coating
-film
-sugar
-compression
Film coating
-polymers, plasticizers, colurants sprayed onto rotating tablets / multiparticulates (MR)
Immediate (non functional)
water soluble, eg. hpmc, pvp
MR (functional)
pH 5-6 eg. ethyl cellulose (EC)
sugar coating
sucrosed based syrup - sugar coating pan
(6 stages)
sealing, sub coating, smoothing, coluring, polishing, printing)
-Readily water soluble - disintegrate
-immediate release
compression coating
less common
complex - compaction of granular particles around tablet core in tablet machine
Tablet attributes
-contains correct dose
-consistent weight, size and appearence
-drug release controlled and reproduceable
-have sufficient mechanical strength
-physically, chemically and microbiologically stable
-formulated for patient acceptence
packaged approprietely
determination of constant drug dose content
-weigh individually 20 tablets at random and determine average mass
-not more than 2 individual tablets deviate from the average mass by more than the percentage deviation shown, and none deviates more than twice the percentage
-accuracy dependednt upon % for drug content - higher drug content more accurate
mimic forced encountered during handling
-tablets must resist friability to ensure doese and appearence is maintained
