Solid Dosage Forms - Tablet Excipients

  • Created by: LBCW0502
  • Created on: 13-10-18 13:19
What is a tablet?
Solid preparation containing a single dose of one or more active substance. Obtained by compressing uniform volumes of particles. Can be with/without excipients. Have lines/break marks/symbol/markings. May be coated
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What are the advantages of tablets as a solid dosage form?
Oral route is convenient and safe, chemical and physical stability, accurate drug dosing, convenient handling, low cost of manufacturing, packaging, shipping, difficult to tamper with
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Give examples of types of tablets
Disintegrating, chewable, effervescent, lozenges, sublingual, buccal
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What are the types of extended release tablets?
Diffusion controlled (membrane), diffusion controlled (matrix), diffusion controlled, erosion controlled, osmosis controlled (dosage forms can use a combination of processes)
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What are the main components in a tablet?
API, fillers, binders, disintegrants, lubricants, anti-adherants, glidants, adsorbents, dissolution retardants, dissolution enhancers, wetting agents, buffers, chelating agents, antioxidants, preservatives, colouring agents, flavouring, coating
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What are fillers?
Provides a sufficient bulk volume for compression
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What are binders (adhesives)?
Added to drug-filler mixture to provide cohesiveness. Most binders used in wet granulation tend to be polymeric. Location of binder within granule can affect quality of granulations produced (e.g. bridges)
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What are disintegrating agents?
Facilitate the break up of a tablet after oral administration. Effervescent tablets might have more disintegrating agents
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What are lubricants used for?
To reduce friction between the powder or granulate and die wall during tablet compression and ejection
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What are the points to remember about lubricants
Only added after all other components are homogeneous. Mixed 2-5 min. Overmixing can decrease dissolution rate. Should not be added prior to wet granulation. Water soluble lubricants can be added as alcoholic solutions (PEGs)
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What are anti-adherants used for?
Prevent sticking of powder or granulate to the die wall during tablet compression and ejection
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What are glidants used for?
Improve flow of powder or granulate from the hopper into die cavity
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What are wetting agents used for?
Aid water uptake, enhancing disintegration and drug dissolution e.g. sodium lauryl sulfate
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What are dissolution retardants used for?
Control release purposes e.g. stearic acid
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What are dissolution enhancers used for?
Alter molecular forces between ingredients and to enhance dissolution of solute in solvent e.g. fructose, surfactants
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What are adsorbents?
Agents that can take up large quantities of liquid e.g. kaolin, magnesium silicate
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What are buffers?
Agents that maintain pH e.g. calcium carbonate
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What are antioxidants?
Agents that protect drug molecules form oxidation e.g. ascorbic acid
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What are chelating agents?
Compounds that form complexes with heavy metal ions inactivating their catalytic activity e.g. EDTA (not as common, more involved in parenteral delivery)
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What are preservatives?
Agents that prevent microbial growth
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What are colourants?
For tablet identification and uniformity of appearance, for disguising off-colour drugs, patient acceptance
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What are flavours?
Agents that improve the taste, especially chewable tablets (affects patient compliance)
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What are sweeteners?
Added primarily to chewable tablets e.g. lactose, sucrose (prevent bitter taste)
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How are tablets compressed?
Operations involved in tablet manufacturing. Single punch tablet press (stamping press, lab scale). Multi-station tablet press (rotary press, industrial scale)
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Describe features of modern tablet presses
More complex but compaction of material between stamps is the same. Increases speed of compaction, different mechanical feeding processes of materials from hopper into die, electronic monitoring of press. 10000 tablets/min. Increased issues
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What is the compression pressure unit?
MPa
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What is elastic deformation?
Particles return to their original shape (deformation disappears completely) upon release of stress
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What is plastic deformation?
Particles do not recover their original shape after release of stress. Force required to initiate plastic deformation - yield/mean deformation pressure
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Is it better to have elastic deformation or plastic deformation?
Plastic deformation
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What is fragmentation?
Fracture occurs when stresses within particles become great enough to propagate cracks. Fragments infiltrate the remaining voids to increase densification
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Describe features of compression inducing particles bonding
Bonding - plastic deformation at the particle interfaces and alignment of particle surface so that the inter-particulate bonding can occur. Mechanical interlocking, melting, hydrophobic interactions, covalent bonding, van der Waals, electrostatic
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What is decompression?
The inter-particulate bonds formed must be sufficiently robust to withstand release of applied pressure. Removal of upper punch relieves axial pressure but radial pressure from die remains. Allows axial elastic recovery to take place
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What is ejection?
The force necessary to eject the tablet from die (ejection force) must be greater than the quotient of residual die wall force exerted from the table and the friction between the tablet and die wall
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Describe features of direct compression?
Commercial availability of directly compressible excipients possessing both good compressibility/flowability. Major advances in tablet compression machinery. Improved positive die feeding. Pre-compression of powder blend
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Describe features of assessment of plastic deformation
Particles do not recover their original shape after release of the stress. Heckel equation. Heckel plot - linear relationship between relative porosity (inverse density) of powder and applied pressure
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Describe how to interpret a Heckel Plot (1)
Slope (K) is the Heckel constant, a material dependent parameter inversely proportional to mean yield pressure. Mean deformation pressure (Py=1/K) minimum pressure required to cause deformation undergoing compression
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Describe how to interpret a Heckel Plot (2)
Intercept A, degree of densification by particle rearrangement. Large values of Heckel constant indicate susceptibility to plastic deformation at low pressures
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What are the common manufacturing problems?
Capping and laminating or splitting, sticking/picking/filming, chipping/cracking, binding
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What is capping?
Occurs when the upper segment of the tablet separates from the main portion of the tablet and comes off as a cap
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What is lamination?
Separation of tablet into two or more distinct layers
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What is sticking?
Occurs due to improperly dried or lubricated granulations causing the tablet surface to stick to the punch surfaces
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What is picking?
A form of sticking in which small portions of the granulate stick to the punch face and grow with each revolution of press, picking out of a cavity on the tablet face
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What is filming?
A slow form of picking and is largely due to excess moisture in the granulation, high humidity, high temperature or loss of highly polished punches faces due to wear
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What is chipping?
The breaking of tablet edges as the tablet leaves the press or during subsequent handling and coating operations
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What is cracking?
Small, fine cracks observed on the upper and lower central surface of tablets, or very rarely on the side walls
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What is binding?
Binding in the die is the term used when tablets adhere seize or tear in the die. A film is formed in the die, ejection of tablet hindered. With excessive binding, tablet sides are cracked/crumble apart
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What is mottling?
An unequal distribution of colour with light or dark spots standing out in an otherwise uniform surface
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Describe features of 3D printing?
Process of making 3D solid objects from a digital file, bio-printing, medical devices, implants, pharmaceutical dosage forms, personalised medicines, enable preparation of multi APIs (levetiracetam)
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What are the advantages of tablets as a solid dosage form?

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Oral route is convenient and safe, chemical and physical stability, accurate drug dosing, convenient handling, low cost of manufacturing, packaging, shipping, difficult to tamper with

Card 3

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Give examples of types of tablets

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Preview of the front of card 3

Card 4

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What are the types of extended release tablets?

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Card 5

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What are the main components in a tablet?

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