10 Types of Tablet Coating Methods in the Pharmaceutical Industry

1. Introduction

Tablet coatings are a critical aspect of pharmaceutical formulation, providing protection, masking unpleasant tastes, and enabling specific drug release profiles. In the pharmaceutical industry, the right pharmaceutical tablet coating can improve stability, patient compliance, and therapeutic performance.

2. Organic Film Coatings

Organic film coatings use polymers dissolved in organic solvents to form a discrete layer on tablets. They are strong barriers to moisture and often used when moisture-sensitive APIs are concerned. Though efficient at producing high-quality coated tablets, organic solvent concerns (toxicity, flammability, environmental impact) mean they are used less than aqueous coatings today.

3. Water-based Film Coatings

Also known as aqueous film coatings, these are the most widely used types of tablet coating today. They consist of polymers (such as HPMC, ethylcellulose), plasticizers, pigments, and other excipients dispersed in water. These coatings are safer, environmentally friendly, and still deliver the benefits of taste masking and protection for film coated tablets.

Film coated tablets examples: Over-the-counter pain relievers (immediate release), vitamins, and many generic medications.

4. Enteric Coating

Enteric coated tablets resist gastric acid and release their contents in the small intestine. This coating is essential for drugs that could irritate the stomach (e.g. NSAIDs like aspirin, diclofenac) or are unstable in acidic environments, or that need to act locally in the intestine (e.g. certain formulations for Crohn’s disease).

This type of pharmaceutical coating ensures targeted delivery and protects both drug and patient.

5. Sustained Release Coating

Sustained release coatings enable a controlled, extended release of the API over several hours. These tablets dissolve gradually in the GI tract, reducing dosing frequency and keeping plasma drug levels steady.

Common types of tablets falling under this category often bear suffixes like “SR” (sustained release), similar to modified release formulations seen in marketed products.

6. Controlled Release Coating

Similar to sustained release, controlled release coatings are engineered to release the drug at a predefined rate, time, or location. They can be based on porous matrices, polymer membranes, or barrier coatings. These coatings are especially useful for drugs with narrow therapeutic windows. A subset of controlled release includes osmotic pump or reservoir systems.

7. Immediate Release Coating

Immediate release coatings are primarily cosmetic or protective (e.g. film coating) but designed to disintegrate rapidly, often in under 15 minutes. Many film coated tablets examples you find on pharmacy shelves are actually immediate release – the coating masks taste or improves appearance, but does not delay drug absorption.

8. Biodegradable Coatings

Biodegradable coatings use polymers that dissolve or break down naturally in the body (e.g., PLGA, natural polymers). These are particularly promising for advanced formulations, including implants or site-specific delivery, where the carrier should disappear after drug release. Though still emerging in the mainstream pharmaceutical tablet coating space, they show strong potential for novel delivery systems.

9. Hot-melt Coating

Hot-melt coating involves applying a molten mixture of waxes or polymers onto tablets. Once cooled, this forms a solid coat without using solvents. Advantages include solvent-free processing and potentially enhanced stability. Challenges include heat sensitivity of APIs and achieving uniform thickness.

10. Nano-coatings

Nano-coatings use nanometer-scale materials or layered structures to add functional properties like improved photoprotection, controlled delivery, or site targeting. Though still largely experimental, nano-coatings have exciting opportunities for targeted or triggered release systems in the future.

11. Photo-sensitive Coating

Photo-sensitive coatings contain light-activated materials that degrade or change properties when exposed to light. They can be used to control when and where the drug is released (e.g., triggered release under UV or IR light). These are cutting-edge in pharmaceutical coating research, especially for targeted therapies or research applications.

12. Compression Coating & Other Methods

Although outside the original list, methods like compression coating (where a core tablet is enclosed by external coating before compression) and electrostatic powder coating are of interest for functional layering or taste-masking applications.

Comparison Table: Coating Types at a Glance

13.Conclusion

Types of tablets based on pharmaceutical coating methods are diverse and tailored to specific drug and patient needs. From traditional organic and aqueous film coatings to advanced nano-coatings and photo-sensitive coatings, each method serves distinct functions—whether for taste masking, protection from environmental degradation, or controlled and site-specific drug release.

Understanding these types of tablet coating and their applications—like enteric coated tablets, film coated tablets examples, and controlled release forms—helps formulators, pharmacists, and regulatory experts optimize drug design and ensure safety and efficacy for patients.

By staying informed of emerging technologies and matching coating strategies to therapeutic goals, pharmaceutical manufacturers can deliver more effective, patient-friendly medications.