1. Introduction to Tablets
Tablets are solid dosage forms containing medicinal substances with or without suitable excipients. They are one of the most commonly used pharmaceutical formulations due to their convenience, accuracy of dosage, stability, and ease of manufacturing.
2. Types of Tablets
Tablets are broadly categorized into coated and uncoated tablets based on the presence or absence of an external coating. This classification significantly impacts their functionality, application, and release profile.
3. Uncoated Tablets
3.1 Definition
Uncoated tablets are compressed dosage forms without any outer covering or coating. They consist of the drug and excipients compressed into a solid mass.
3.2 Characteristics
• Simple in structure.
• Quick to manufacture.
• Expose the active pharmaceutical ingredient (API) directly to the external environment.
• Dissolve or disintegrate quickly upon ingestion.
3.3 Advantages
1. Economical: Cost-effective due to fewer processing steps.
2. Faster Dissolution: Dissolves faster than coated tablets as there is no barrier.
3. Easier Identification: Surface markings or color can be directly applied for easy identification.
4. Suitable for Immediate-Release Formulations: Ideal for drugs requiring rapid onset of action.
3.4 Disadvantages
1. Poor Taste Masking: Bitter or unpleasant-tasting APIs cannot be masked.
2. Low Protection: Susceptible to environmental factors like moisture, light, and oxidation.
3. Limited Aesthetic Appeal: May lack the polished or attractive appearance of coated tablets.
3.5 Applications
• Commonly used for immediate-release formulations.
• Suitable for stable and non-irritating drugs.
4. Coated Tablets
4.1 Definition: Coated tablets have an additional layer or layers of coating applied to the tablet core. The coating can be functional (e.g., controlled-release) or non-functional (e.g., aesthetic or protective).
4.2 Types of Coatings
1. Sugar Coating:
• Comprises sugar and other water-soluble excipients.
• Provides a glossy, sweet layer to improve taste and appearance.
2. Film Coating:
• Thin polymer-based layer applied to the tablet surface.
• Used for protection, taste masking, or controlled release.
3. Enteric Coating:
• Special pH-sensitive coating that resists dissolution in the acidic stomach but dissolves in the alkaline intestine.
• Protects the drug from stomach acid and prevents gastric irritation.
4. Compression Coating:
• Involves compressing an outer layer around the core.
• Allows incorporation of incompatible drugs.
4.3 Characteristics
• Provide a protective barrier.
• May alter the drug’s release profile.
• Enhance appearance and patient compliance.
4.4 Advantages
1. Improved Stability: Protects the drug from environmental factors.
2. Taste Masking: Covers bitter or unpleasant-tasting APIs.
3. Controlled Release: Enables modifications in drug release (e.g., delayed or extended release).
4. Reduced Irritation: Prevents direct contact of the drug with the gastric mucosa.
5. Enhanced Aesthetics: Improves appearance with uniform coloring and gloss.
4.5 Disadvantages
1. Higher Cost: Additional steps increase manufacturing expenses.
2. Complex Production: Requires advanced equipment and skilled operators.
3. Longer Processing Time: Coating application can be time-consuming.
4.6 Applications
• Widely used for drugs requiring taste masking.
• Suitable for controlled-release formulations.
• Used for drugs sensitive to stomach acid or causing gastric irritation.
5. Comparison: Coated vs. Uncoated Tablets
| Aspect | Coated Tablets | Uncoated Tablets |
| Structure | Has an additional layer of coating. | Does not have an outer coating. |
| Manufacturing | Requires additional processing steps. | Simpler and quicker to manufacture. |
| Cost | More expensive due to coating materials. | Economical. |
| Appearance | Glossy and polished; highly aesthetic. | Simple and less appealing. |
| Stability | Better protection against environmental factors. | More susceptible to degradation. |
| Taste Masking | Effective in masking unpleasant tastes. | Ineffective for taste masking. |
| Release Profile | Can be modified (e.g., delayed release). | Usually immediate-release. |
6. Common Excipients Used in Tablet Coating
1. Polymers: Hypromellose (HPMC), Ethylcellulose, Eudragit.
2. Plasticizers: Polyethylene glycol (PEG), Dibutyl sebacate.
3. Colorants: Titanium dioxide, Iron oxides.
4. Solvents: Water, Ethanol, Isopropanol.
7. Evaluation of Coated and Uncoated Tablets
7.1 Physical Properties
• Weight variation.
• Hardness.
• Friability.
7.2 Chemical Properties
• API content uniformity.
• Stability studies.
7.3 Performance Tests
• Disintegration time.
• Dissolution profile.
• Drug release kinetics.
Both coated and uncoated tablets have their unique advantages and limitations. The choice depends on the drug’s properties, desired release profile, and patient requirements. Coated tablets are suitable for sensitive drugs requiring taste masking or modified release, whereas uncoated tablets are preferred for their simplicity, cost-effectiveness, and rapid action.
