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Flashcards in Solid Oral Dosage Forms 4 Deck (28):

Types of excipient: tablets and capsules

Diluent/filler- to increase size of tablet or fill a capsule shell, to help form compacts or plugs
Binder- use to form granules, either dry or in solution
Wetting agent and stabilisers, colourants and flavours


Diluents: sugars

Good properties, water soluble
Lactose- most commonly used, available in a variety of forms- crystalline and amorphous, spray dried forms used for direct compression
Several sugars/sugar alcohols are used for their taste properties e.g. sucrose, glucose, mannitol and sorbitol
Used in chewable tablets and lozenges


Diluents: starches

Variety of plant sources, mainly for capsules, advantage low cost e.g. maize, potato, rice and local plants
Modified starches used in both tablets and capsules- pregelatinised, better flow properties, starch 1500, physically processed maize starch to improve flow


Diluents: inorganics

Calcium phosphate- dicalcium phosphate dehydrate and anhydrous, insoluble but hydrophilic, readily wetted; tribasic calcium phosphate
Calcium carbonate
Both used as a calcium source in nutraceuticals


Diluents: organics

Microcrystalline cellulose
Powdered (microfine) cellulose
Both have good compaction properties, large change in volume with compression force



Adhesive materials that hold the granules together
Wet binders- typically aqueous preparation, sometimes added to dry mix and then wetted during granulation
Dry binders- material with good compaction properties added to formulation to improve the compact strength, celluloses


Wet binders

Cellulose derivatives
Maltitol, maltodextrin
Starch paste
Polyethylene glycol
Water principal solvent, if cannot be used then replaced with ethanol or isopropanol


Dry binders

Materials that deform plastically and fill voids in tablet mass e.g. microcrystalline cellulose



Break tablets apart and disrupt powder plug in capsules
Standard Disintegrants: starch, maize, potato, do not work in hard capsules
Super Disintegrants: sodium starch glycolate, crospovidone, croscarmellose sodium



Stop materials adhering to moving metal parts on tabletting and capsule filling machines
Magnesium stearate- most used excipient in SODF
Sodium stearyl fumarate
Stearic acid
Polyethylene glycol


How do tablet lubricants work?

Boundary lubricants- form films at surface of die wall and tablet e.g. magnesium stearate
Stearic acid- melts to form a boundary layer



Problem with sticking on faces of tablet punches particularly with embossed punches- fault called picking
Magnesium stearate has a secondary role in preventing sticking
Talc and starches are also used



Powders that coat other particles and reduce inter-particulate forces improving flow of the mass
Colloidal silicon dioxide


Glidants and lubricants

Both act on the surface of particles
If not properly dispersed, do not function
A minimum optimum concentration gives maximum effect and if exceeded adverse effects occur
Concentration to use related to size of surface to be covered


Wetting agents

Added to improve wetting of hydrophobic actives
Sodium lauryl sulphate
Polysorbate 80


Stabilisers, flavours and colourants

Moisture scavengers- colloidal silicon dioxide
Flavours- used for taste masking of bitter active
Colourants- soluble dyes and insoluble pigments


What is colour?

Requires light source, object, observer, eye or instrument, matching colour by mixing primary colours


Pharmaceutical colourants

Dyes- water soluble, azo, non-azo
Pigments- water insoluble, titanium dioxide, iron oxides, lake form of soluble dyes


Iron oxide pigments

Restrictions in USA- amount used as a colourant must not exceed 5mg of elemental iron per day
Iron oxide and absorption of iron- solubility in artificial gastric juice after 4 hours


What factors influence tablet and capsule formulation?

Size of dose
API properties- compactability, fluidity, solubility, stability


Influence of API dose

Low dose (<25mg): most of tablet or capsule formulation will be excipient, challenge is content uniformity
High dose (>250mg): most of tablet or capsule will be API, challenge is compactability and fluidity
API solubility important for both, governs selection of excipient


Effervescent tablets

Disintegration by release of gas, carbon dioxide
Reaction between carbonate or bicarbonate and weak acid, citric or tartaric
Prepared by direct compression or by:
Wet fusion: citric acid moistened and added to sodium bicarbonate and granulated, granules dired at 70c
Heat fusion: dry powders blended with citric acid monohydrate and heated to produce granules


Chewable tablets

mechanical disintegration in the mouth
No disintegrant in the formulation
Diluents chosen for their sensory properties
Flavours added to improve taste


Buccal/sublingual tablets

Standard tablets, small size- formulated for fast disintegration
Designed for absorption in buccal cavity achieve rapid action or to avoid first pass metabolism
Sublingual, placed under the tongue
Buccal, placed in side of cheek


Orally disintegrating tablets

Disintegrate in <10 seconds, equivalent to standard immediate release tablets
Designed for aiding compliance of patients who have difficulty in swallowing standard tablets and capsules
Active people who have no access to water for swallowing standard SODF
Formulation: many patented processes, proprietary information


Types of orally disintegrating tablets

Standard tablets
Compression moulded tablets
Freeze-dried tablets
Extra challenges in formulation- taste masking , coating of powder particles, using effervsecence


Orally disintegrating tablets compressed tablet formulation

Rapidly soluble compounds- sucrose, amorphous, mannitol, lactose, amorphous or partly amorphous
Super Disintegrants- up to 10% w/w
Moderate compression forces- achieve high porosity with adequate hardness and friability


Freeze dried tablets

Solution made and dispensed into pre-formed blisters, passed through a cryogenic freezing process that control ice crystal size, hence tablet porosity
Frozen blisters transferred to large freeze driers
Finally open blisters have lids added and heat sealed