Tablet Coating Pan Guide: Equipment, Process & Troubleshooting for Pharma Labs
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Why Tablets Are Coated
Tablet coating is one of the most important steps in pharmaceutical manufacturing. Coatings serve multiple critical functions: masking bitter taste, protecting API from moisture and light degradation, controlling drug release rate (immediate vs. extended release), improving swallowability, and providing product identification through color coding. A quality coating pan is the heart of this process.
SciMed's Tablet Coating Pan is constructed from pharmaceutical-grade stainless steel and designed for bench-scale to pilot-scale coating operations in research labs, compounding facilities, and small pharma manufacturers.
Types of Tablet Coating
- Sugar coating (dragee): Traditional multi-step process applying sucrose-based layers. Creates smooth, glossy, sweetly-masked tablets. Labor-intensive but produces attractive product.
- Film coating: Thin polymer film (HPMC, Eudragit, PVA) applied by spray. Faster, more precise, better moisture protection. Industry standard for modern tablet coating.
- Enteric coating: Acid-resistant polymer (Eudragit L/S, HPMCP) protects API from stomach acid and releases drug in the intestine — critical for acid-labile APIs and bowel-targeted drugs.
- Modified-release coating: Controls dissolution rate to achieve extended, delayed, or pulsatile drug release profiles.
The Coating Process: Step by Step
- Pre-heat the pan to operating temperature (typically 40–50°C inlet air). Pre-warming reduces moisture uptake during initial spray.
- Load tablets into the coating pan. Optimal fill is 50–70% of pan volume to ensure uniform tumbling.
- Prepare coating solution — dissolve or disperse polymer, plasticizer, colorant, and any other excipients in solvent (water or organic solvent).
- Spray coating solution onto the tumbling tablet bed. Spray rate, atomization pressure, pan speed, and inlet air temperature must all be controlled simultaneously.
- Dry between passes — allow each coating layer to dry before applying the next to prevent over-wetting and tablet sticking.
- Monitor weight gain — film coating typically targets 2–5% weight gain; enteric coatings may require 8–15%.
- Final polishing — optional wax or polish application for high-gloss finish.
Common Coating Defects and Solutions
| Defect | Cause | Solution |
|---|---|---|
| Sticking / picking | Spray rate too high, insufficient drying | Reduce spray rate, increase inlet temperature |
| Orange peel texture | Poor atomization, spray too far from bed | Increase atomization pressure, move spray closer |
| Color mottling | Uneven spray, poor tablet movement | Increase pan speed, check spray pattern uniformity |
| Logo bridging | Over-coating, slow drying | Reduce spray rate, lower coating solution viscosity |