tablets

Define a tablet

A tablet is a solid dosage form manufactured by compressing uniform volumes of powder containing one or more active pharmaceutical ingredients (APIs) and excipients. Tablets may also be produced by moulding or freeze-drying. They are intended to be swallowed whole, chewed, dissolved, dispersed in water or retained in the mouth. Tablets may be coated and may provide immediate or modified drug release.

what are tablet advantages

Advantages include:

• Good patient compliance

• Convenient handling, storage and administration

• Accurate dosing

• Chemical, physical and microbial stability

• Robust and inexpensive manufacture

disadvantages of tablets

Disadvantages include:

• Usually provide systemic drug delivery only

• Poor bioavailability for poorly soluble drugs

• Must usually be swallowed

• Subject to first-pass metabolism

• Possible gastrointestinal irritation

• Extensive formulation development required

examples of tablet types

• Immediate-release: disintegrating, chewable, effervescent, compressed lozenges, sublingual and buccal tablets.

• Modified-release: prolonged-release, delayed-release and pulsatile-release tablets.

Compare the different immediate-release tablets and explain drug release from tablets.

Immediate-release tablets rapidly release drug after administration.

Disintegrating tablets are swallowed whole. Drug release occurs by:

Disintegration → Dissolution → Absorption

Disintegration depends upon formulation and manufacturing, dissolution depends on drug solubility and particle size, while absorption depends largely upon lipophilicity.

Chewable tablets undergo mechanical disintegration in the mouth and usually contain flavours and colourings. Examples include vitamins and Gaviscon.

Effervescent tablets are dispersed in water and contain carbonate/bicarbonate with citric or tartaric acid, releasing carbon dioxide to speed disintegration and dissolution.

Compressed lozenges dissolve slowly in saliva without disintegrants and provide local or systemic action. They commonly contain water-soluble binders and fillers.

Sublingual tablets are placed under the tongue and buccal tablets between the cheek and gum. They provide rapid systemic delivery while avoiding first-pass metabolism. Examples include nitroglycerin and nicotine.

Describe the properties of an ideal tablet blend

An ideal tablet blend should be:

Homogeneous to ensure dose uniformity

Free-flowing for efficient die filling

Cohesive and adhesive to form strong tablets

Non-adherent to punches and dies

explain the functions of tablet excipients.

Fillers/Diluents

Increase tablet size, density and strength.

Disintegrants

Promote rapid tablet breakup.

Binders

Provide mechanical strength.

Glidants

Reduce interparticulate friction and improve flow.

Lubricants

Reduce friction between tablets and machine tooling.

Compare direct compression and granulation

Direct compression involves mixing drug and excipients followed by immediate compression.
Granulation forms granules before compression.

advantages of direct compression

• Lower production costs

• Faster manufacture

• Faster drug dissolution

disadvantages of direct compression

• Requires specialist excipients

• Requires excellent powder flow

• Risk of segregation

• Poor compactability

• Poor colour uniformity

advantages of granulation

• Improves homogeneity

• Prevents segregation

• Improves flow

• Improves compactability

• Increases bulk density

• Improves colour uniformity

disadvantages of granulation

Disadvantages:

• Increased production cost

• Longer manufacture

• Risk of hydrolytic degradation

describe the stages of tablet manufacture.

1. Mixing

2. Agglomeration (granulation)

3. Drying

4. Milling

5. Final blending

6. Compression

Compare single-punch and rotary tablet presses

A single-punch press has one set of punches and produces up to approximately 200 tablets/min. It is mainly used for formulation development and clinical trial batches.

A rotary press contains multiple punch stations (3–60) and produces more than 10,000 tablets/min, making it suitable for large-scale manufacture.

explain problems encountered during tablet compression. 5

Capping

Top of tablet separates due to trapped air.

Lamination

Tablet separates into horizontal layers due to trapped air, insufficient binder, excess lubricant or low moisture.

Sticking

Material adheres to punch faces.

Picking

Material sticks inside punch engravings or logos.

Chipping

Tablet edges break.

what does good manufacturing requires control of 7

• Homogeneity

• Segregation

• Flowability

• Compression

• Compactability

• Friction

• Adhesion

whats the reason for tablet coating

Tablet coating involves applying an outer layer to improve tablet performance.

Reasons for coating include:

• Drug protection

• Taste masking

• Easier swallowing

• Improved appearance

• Product identification

• Easier handling

• Increased tablet size

• Modified drug release

what are the 3 different coating methods

Film coating

Most common method.

Contains polymers, plasticisers and colourants.

Can produce immediate-release or modified-release tablets.

Sugar coating

Traditional method.

Uses sucrose syrup.

Applied in six stages:

• Sealing

• Subcoating

• Smoothing

• Colouring

• Polishing

• Printing

Produces immediate-release tablets.

Compression coating

Granules compressed around a tablet core.

Technically more complex but useful for specialised formulations.

Describe the ideal tablet quality attributes 7

Ideal tablets should:

• Contain the correct dose

• Have consistent weight, size and appearance

• Provide reproducible drug release

• Possess adequate mechanical strength

• Be physically, chemically and microbiologically stable

• Be acceptable to patients

• Be appropriately packaged

describe all of the bp quality tests

Uniformity of mass

20 tablets weighed individually.

No more than two tablets may exceed permitted deviations and none may exceed twice the limit.

Friability

Asesses resistance to abrasion

• Weight loss exceeds 1%

• Tablets crack, cleave or break.

Fracture resistance

Measures crushing force.

Typical RGU mean:

40–100 N.

BP requires reporting mean, minimum and maximum values

Describe BP disintegration and dissolution tests .

Disintegration test

Six tablets tested.

Purified water.

37 ± 2°C.

Standard time: 15 minutes.

If one or two tablets fail, twelve additional tablets are tested. At least 16 of 18 tablets must pass.

Coated tablets may require longer testing times (e.g. 60 minutes).

Dissolution test

Six tablets placed into dissolution medium maintained at 37 ± 0.5°C using basket or paddle apparatus.

Drug-specific dissolution media are used according to the BP monograph.

Typical specification:

Greater than 70–75% drug release within 45 minutes.

Disintegration alone does not guarantee adequate dissolution or absorption.

explain the relationship between tablet disintegration, dissolution and drug absorption.

Drug release occurs by:

Disintegration → Dissolution → Absorption

Disintegration breaks tablets into granules and particles.

Dissolution converts drug into solution before absorption from the gastrointestinal tract