Tablet coating is one of the most important steps in pharmaceutical manufacturing. In simple terms, it’s like “putting a jacket” on the tablet. This coating doesn’t just improve appearance and taste—it also protects the drug, controls where and how it’s released in the body, and enhances patient compliance.
For professionals involved in R&D, production, or equipment procurement, choosing the right coating type and process is critical to producing high-quality, GMP-compliant medicines.
Today, the three most common tablet coating types used in the pharmaceutical industry are sugar coating, film coating, and enteric coating.
With technological advancement, newer coating technologies such as aqueous coating and controlled-release coating have also become widespread. Each serves specific purposes—such as protecting the active ingredient, improving swallowability, or enabling targeted intestinal release.
What Is Tablet Coating?
Imagine coating a chocolate bean with sugar—that’s essentially what tablet coating does. Tablet coating refers to the process of applying a uniform layer of polymer or sugar solution onto the surface of compressed tablets.
Why Do We Coat Tablets?
- Protect the active ingredient: Prevents moisture, oxidation, and light exposure, extending shelf life.
- Improve patient experience: Masks unpleasant tastes and makes tablets easier to swallow.
- Control drug release: Ensures the tablet dissolves only in specific areas, such as the intestine.
- Brand differentiation: Adds colors and logos for easy identification by doctors and patients.
The process is typically performed in specialized coating machines that spray and dry the coating solution while tablets tumble continuously, ensuring an even coating layer. Common equipment includes automatic tablet coating machines, perforated drum coaters, and fluid bed coaters.
The Three Main Types of Tablet Coating
1. Sugar Coating
Sugar coating is the oldest and most traditional coating technique. It involves applying multiple layers of sucrose-based syrup to build up a glossy, smooth finish.
Process steps: sealing → subcoating → smoothing → coloring → polishing
Advantages:
- Produces a bright, candy-like appearance.
- Excellent taste masking capability.
Disadvantages:
- Labor-intensive and time-consuming.
- Increases tablet weight by 30–50% and size significantly.
Applications:
Commonly used for chewable tablets, herbal medicines, and vitamins where appearance and taste are important.
2. Film Coating
Film coating is the modern industry standard. Instead of sugar syrups, it uses polymer-based coating solutions to form a thin protective film over the tablet.
Typical formulation components:
- Film-forming agents: HPMC (Hydroxypropyl Methylcellulose), PVA (Polyvinyl Alcohol)
- Plasticizers: PEG 400, triethyl citrate – to prevent film cracking
- Colorants: Titanium dioxide for opacity and color
- Solvents: Water or ethanol (water-based systems are now preferred)
Advantages:
- Fast and efficient—ideal for large-scale production.
- Minimal weight gain (2–3%) without changing tablet size.
- Offers protection and can support controlled-release designs.
Disadvantages:
- Requires precise control of process parameters (spray rate, air temperature, pan speed).
- Improper settings can cause rough surfaces or tablet sticking.
Applications:
Suitable for nearly all immediate-release and modified-release tablets.
3. Enteric Coating
Enteric coating is designed to protect the drug from stomach acid and allow it to dissolve only in the intestine (alkaline environment).
Why use it?
- To protect acid-labile drugs (e.g., omeprazole).
- To prevent gastric irritation (e.g., aspirin).
- To enable site-specific intestinal release.
Common materials:
Eudragit® polymers, HPMCP (Hydroxypropyl Methylcellulose Phthalate). These materials remain stable in acidic environments but dissolve in alkaline conditions.
Advantages:
- Ensures targeted release in the intestine.
- Improves drug stability and patient safety.
Disadvantages:
- Higher material and processing costs.
- Requires stringent testing to confirm acid resistance and intestinal solubility.
Typical performance tests:
- No disintegration after 2 hours in 0.1N HCl.
- Complete dissolution within 60 minutes in pH 6.8 phosphate buffer.
Applications:
Used for acid-sensitive or stomach-irritating drugs like enzymes, antibiotics, and proton pump inhibitors.
Advanced and Specialized Coating Technologies
Modern pharmaceutical manufacturing has expanded beyond the basic three coating types to include several advanced options:
- Controlled/Extended-Release Coating: Allows gradual drug release over hours or days by controlling coating thickness and permeability.
- Moisture-Protective Coating: Prevents degradation of moisture-sensitive drugs.
- Hot-Melt Coating: Uses molten materials instead of solvents—eco-friendly and solvent-free.
- Electrostatic Coating: Uses electric charge to ensure uniform coverage.
- Aqueous Coating: Replaces organic solvents with water—safer, cleaner, and now an industry trend.
Tablet Coating Process and Equipment
Main steps:
- Coating solution preparation: Mix polymers, plasticizers, and pigments.
- Spraying: Evenly spray atomized coating liquid onto tumbling tablets.
- Drying: Use heated air to evaporate solvent and form the coating layer.
- Curing: Sometimes requires post-drying or “baking” to enhance film strength and stability.
- Inspection: Check for defects such as cracks, orange peel, or uneven color.
Equipment options:
- Traditional coating pan: Simple, low-cost option.
- Perforated drum coater: High efficiency, uniform drying.
- Fluid bed coater: Ideal for granules and tablets; offers excellent coating uniformity.
How to Choose the Right Coating Type
Related Questions
What’s the difference between film coating and sugar coating?
Film coating is faster and lighter, while sugar coating forms a thicker, shinier layer.
Why use enteric coating?
To protect the drug from stomach acid or to prevent gastric irritation.
How can coating problems be avoided?
Most surface defects—like roughness or sticking—come from improper spray, drying, or pan speed control. Fine-tuning parameters is key.
What’s the latest trend in tablet coating?
Aqueous and solvent-free systems using PAT (Process Analytical Technology) for real-time monitoring and precision control.
If you’re looking for reliable tablet coating solutions, contact LTPM CHINA for expert guidance and advanced coating systems.
We offer fully automatic tablet coating machines, fluid bed coaters, and complete solid dosage production lines—all customizable and backed by a five-year warranty.