Tablet – Pharmaceutical Technology

Tablet is a solid unit dosageform containing one or more active pharmaceutical ingredients (APIs), with or without excipients, prepared by or other suitable manufacturing processes.

In simple words, a tablet is a solid medicine prepared in a definite dose, usually by compressing powder or granules into a specific shape.

Examples: Paracetamol tablet, Metformin tablet, and Aspirin tablet.

Types of Tablets

Tablets can be classified according to their route of administration, method of preparation, and drug-release characteristics.

Important: Enteric-coated tablets should generally not be crushed or chewed because this may damage the protective coating. Modified-release tablets also require product-specific instructions.

Ideal Properties of a Tablet

An ideal tablet should have the following properties:

1. It should contain the correct amount of drug.

2. It should have uniform weight and drug content.

3. It should have sufficient mechanical strength.

4. It should not break or chip easily during handling.

5. It should disintegrate and release the drug as intended.

6. It should remain stable during storage.

7. It should have an acceptable appearance, size, shape, and taste where relevant.

8. It should be free from contamination and manufacturing defects.

9. It should be easy to package, transport, and administer.

Ingredients of a Tablet (Excipients)

Excipients are substances added to a tablet formulation other than the active pharmaceutical ingredient. They help in manufacturing, stability, appearance, and drug release.

Remember the difference:

• Binder: Holds particles together.

• Disintegrant: Helps the tablet break apart.

• Lubricant: Reduces friction.

• Glidant: Improves powder flow.

• Diluent: Adds bulk.

Methods of Tablet Manufacturing

The main methods are:

Comparison of Manufacturing Methods

6. Steps of Tablet Manufacturing

A. Wet Granulation Method

The general manufacturing sequence is:

Explanation of Important Steps

1. Dispensing: Raw materials are weighed according to the approved batch manufacturing record.

2. Sifting: Materials are passed through a suitable sieve to remove lumps and obtain a suitable particle size.

3. Dry mixing: The API and selected excipients are mixed uniformly.

4. Binder addition: A binder solution or suitable binder system is added.

5. Granulation: Powder particles are converted into granules.

6. Drying: Excess moisture is removed to the specified limit.

7. Sizing: Dried granules are passed through a suitable screen to obtain a suitable size distribution.

8. Lubrication: Lubricant and other final-blend ingredients are mixed with the granules.

9. Compression: Granules are compressed into tablets using a tablet compression machine.

10. Coating: A coating is applied if required by the formulation.

11. Inspection and quality control: Tablets are checked for appearance and applicable quality specifications.

12. Packaging: Approved tablets are packed in suitable containers or blister packs.

Note: Actual processing steps and in-process controls depend on the approved formulation and manufacturing procedure. Direct compression and dry granulation follow different process sequences.

7. Tablet Compression Machine

A tablet compression machine converts powder or granules into tablets by applying compression force.

Main Parts and Their Functions

Types of Tablet Compression Machines

• Single-punch machine: Uses one punch-and-die station at a time; suitable for laboratory work and small-scale production.

• Rotary tablet press: Uses multiple punch-and-die stations on a rotating turret; suitable for high-volume production.

8. Quality Control Tests for Tablets

Tablet quality control ensures that tablets meet the required specifications for identity, strength, purity, performance, and consistency.

1. Weight Variation / Uniformity of Mass

Checks whether individual tablet masses comply with the applicable pharmacopoeial requirements. It helps assess consistency of tablet mass.

2. Hardness / Crushing Strength

Measures the force required to break a tablet under specified test conditions. Tablets need adequate strength for handling and transport.

3. Friability Test

Evaluates the tendency of tablets to lose mass through abrasion or mechanical stress. A commonly used pharmacopoeial reference limit for many conventional uncoated tablets is not more than 1.0% mass loss, where applicable.

4. Disintegration Test

Determines whether tablets break down into particles under specified test conditions within the required time.

5. Dissolution Test

Measures the rate and extent to which the drug dissolves in a specified medium under defined conditions.

6. Assay

Determines the amount or concentration of the API in the tablet sample.

Other Important Tests

• Uniformity of dosage units: Evaluates whether individual dosage units contain an appropriate amount of the drug. Depending on the monograph, this may involve content uniformity or an applicable mass-variation procedure.

• Appearance: Checks colour, shape, surface, markings, coating, and visible defects.

• Dimensions: Checks tablet thickness and diameter, where specified.

• Moisture content: Measures moisture when required by the formulation or specification.

• Identification test: Confirms the identity of the API.

• Impurity testing: Evaluates specified impurities and degradation products.

• Microbial quality: Tested where required for the product.

Important for QA/QC interviews: Not every test is mandatory for every tablet. The applicable pharmacopoeia, approved product specification, and regulatory requirements determine which tests and acceptance limits apply.

9. Common Tablet Defects

QA principle: When a defect occurs, the batch should be assessed according to approved procedures. The cause should be investigated, documented, and addressed through the appropriate quality system, including CAPA when warranted. Do not simply adjust machine settings without following authorized procedures.

10. In-Process Quality Control (IPQC)

IPQC means In-Process Quality Control. It involves checks performed during manufacturing to ensure that the process remains under control.

Typical tablet-manufacturing checks include:

• Blend or granule appearance and relevant process parameters.

• Granule moisture content, where applicable.

• Tablet weight or mass.

• Tablet thickness and diameter.

• Tablet hardness or crushing strength.

• Friability, where required.

• Disintegration, where required.

• Appearance and identification markings.

• Compression-machine parameters and documented adjustments.

The sampling frequency and acceptance limits must follow the approved batch documentation and applicable procedures.

11. Advantages of Tablets

1. Accurate and convenient unit dosing.

2. Generally easy to handle, transport, and store.

3. Good stability for many formulations.

4. Suitable for large-scale, economical production.

5. Can be manufactured in different shapes, sizes, and release profiles.

6. Packaging and labelling are convenient.

7. Can mask unpleasant taste using suitable coatings or other formulation techniques.

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12. Disadvantages of Tablets

1. Some patients have difficulty swallowing them.

2. Not all APIs can be formulated easily as tablets.

3. Drug release can be affected by formulation and manufacturing variables.

4. Some tablets may be unsuitable for patients who require rapid administration or cannot swallow solid dosage forms.

5. Certain tablets are sensitive to moisture, heat, or light.

6. Modified-release and enteric-coated products may be damaged if crushed or split inappropriately.

13. Important Differences for Exams and Interviews

Disintegration vs Dissolution

A tablet may disintegrate but still fail to meet its dissolution requirement.

Hardness vs Friability

Binder vs Disintegrant