School of Pharmacy and Paramedical Sciences, K.K University, Nalanda, Bihar
Tablet coating is a vital process in pharmaceutical manufacturing that enhances the functionality, stability, and patient acceptability of oral dosage forms. Coatings can be classified into sugar coating, film coating, enteric coating, and functional types, each designed to fulfill specific therapeutic and aesthetic objectives. Composed of polymers, plasticizers, colorants, and opacifiers, coating formulations are carefully optimized to provide durability, uniformity, and performance. Advantages of coatings include protection of active ingredients from environmental factors, taste masking, improved swallowability, aesthetic enhancement, and enabling controlled or targeted drug release. This review delves into the principles, composition, and benefits of tablet coatings, emphasizing their critical role in ensuring patient compliance, product stability, and therapeutic efficacy.
Tablet coating is a pivotal step in pharmaceutical manufacturing, enhancing both the functionality and appeal of oral dosage forms. Dating back to the early 19th century, sugar coating was one of the first techniques employed to improve the appearance and taste of tablets. Over the decades, advancements in material science and process technologies have transformed coating methods into highly sophisticated applications that not only improve patient compliance but also address critical therapeutic and manufacturing challenges. Modern tablet coatings serve multiple purposes, ranging from taste masking and ease of swallowing to controlled drug release and API protection. For instance, enteric coatings prevent drug degradation in the acidic gastric environment and ensure delivery to the intestines, as seen with proton pump inhibitors like omeprazole. Similarly, sustained-release coatings in drugs like metformin allow for consistent therapeutic levels over an extended period, reducing dosing frequency and enhancing patient adherence.
The coating process typically involves the application of a thin, uniform layer of materials such as polymers, plasticizers, opacifiers, and colorants. Polymers like hydroxypropyl methylcellulose (HPMC), ethylcellulose, and cellulose acetate phthalate are widely used for their mechanical strength and flexibility. Plasticizers like polyethylene glycol (PEG) or triacetin enhance the film's durability, while opacifiers such as titanium dioxide protect the drug from light-induced degradation. Advanced coating technologies, such as fluidized bed systems and pan coaters, have enabled precise control over the coating thickness, uniformity, and functionality.
Today, tablet coatings play a critical role in addressing diverse pharmaceutical needs. For example, film coatings are preferred for their efficiency and minimal impact on tablet size, while functional coatings offer innovative solutions for targeted delivery and extended release. According to market reports, the global tablet coating market was valued at approximately $3.5 billion in 2020 and is expected to grow steadily due to the increasing demand for improved drug formulations. This review provides a comprehensive examination of tablet coating types, compositions, and applications. By delving into the principles and innovations behind this process, it highlights the critical role of coatings in enhancing product quality, therapeutic efficacy, and patient compliance.
Recent Trends in Tablet Coating Technology
The pharmaceutical industry is continuously evolving, and tablet coating technologies are no exception. Advances in materials, processes, and equipment have transformed coatings from simple protective layers to highly functional systems that enhance drug performance and manufacturing efficiency. Below are some of the most notable recent trends in tablet coating technology:
1. Functional Coatings for Controlled Drug Release
Functional coatings are gaining significant attention for their ability to control drug release profiles. These coatings are designed to enable modified release (e.g., sustained, delayed, or pulsatile release) to improve therapeutic efficacy and patient compliance.
Trend Example: Use of pH-sensitive polymers, such as methacrylic acid copolymers, in enteric coatings for targeted release in the intestines.
Advances: Multi-layered coatings with dual functionality, combining immediate-release and sustained-release properties in a single dosage form.
2. Advanced Polymers and Coating Materials
Emerging coating materials offer better performance, flexibility, and biocompatibility.
Natural Polymers: Increased use of plant-derived polymers like guar gum, alginates, and pullulan for eco-friendly and biodegradable coatings.
Amorphous Solid Dispersions: Polymers used in coatings to stabilize poorly soluble APIs and enhance bioavailability.
Nanocoatings: Ultra-thin, nanostructured coatings that provide precise control over drug release and absorption kinetics.
3. Solvent-Free Coating Technologies
Traditional coating methods often involve organic solvents, which pose environmental, safety, and regulatory concerns. Recent innovations aim to eliminate or reduce solvent use:
Hot-Melt Coating: Utilizes waxes or lipids to form coatings without solvents.
Pharmacological Applications:
Tablet Coating: Films that offer controlled release, taste masking, and moisture protection are applied to tablets via hot melt coating.
Hot melt coating can be utilized in fluid bed systems, which are frequently employed to coat powders and grains.
Pellet coating and granulation: Continuous pharmaceutical operations employ hot melt extrusion for pellet coating and granulation.
The benefits of hot melt coating is
Solvent-Free: The environmentally benign method of hot melt coating eliminates the need for a solvent.
Quick Processing: It enables quicker processing times, which boost output.
Versatility: A range of substrates, such as tablets, granules, and pellets, can be coated with hot melt technology.
Regulated Coating Thickness: It makes it possible to regulate coating thickness, guaranteeing consistent application precisely.
Dry Powder Coating: Employs electrostatic charges to coat tablets with powdered polymers.
Aqueous Film Coating: Replacing organic solvents with water-based systems for a safer and more sustainable process.
4. Smart Coatings and Digital Integration
Smart coatings are designed to respond to external stimuli or provide real-time data for enhanced patient care.
Stimuli-Responsive Coatings: Coatings that release drugs in response to environmental triggers like temperature, pH, or enzymes.
Digital Sensors: Tablets embedded with sensors or coatings that provide adherence data to healthcare providers. For example, digital pills integrated with smart coatings can transmit ingestion confirmation to a mobile app.
5. 3D Printing and Personalized Coatings
3D printing is revolutionizing tablet manufacturing, allowing precise customization of coating thickness, composition, and drug release profiles.
Personalized Medicine: Coatings can be tailored to individual patient needs, including specific release timings or multi-drug combinations.
Layer-by-Layer (LbL) Technology: 3D-printed coatings enable layering of different materials for complex release profiles.
6. Taste-Masking and Patient-Centric Coatings
With the growing emphasis on patient-centric drug design, taste-masking coatings have become increasingly sophisticated, especially for pediatric and geriatric populations.
Recent Innovations: Microencapsulation of bitter drugs and flavored coatings to improve palatability.
Thin, Fast-Dissolving Films: Coatings designed to dissolve quickly in the mouth, ideal for orally disintegrating tablets (ODTs).
7. Continuous Manufacturing in Coating Processes
The adoption of continuous manufacturing technologies is reshaping tablet coating processes to improve efficiency and reduce production costs. First one is Trend Example & Impact
Trend Example: Continuous coaters with real-time process monitoring and automated controls for precision and scalability.
Impact: Reduced production time, lower waste, and consistent product quality.
8. Green and Sustainable Coating Approaches
Sustainability is a growing focus in pharmaceutical manufacturing, and coating processes are aligning with this trend.
Water-Based Systems: Reducing the reliance on organic solvents.
Biodegradable Coatings: Use of natural and eco-friendly polymers to meet environmental regulations and reduce waste.
9. Improved Equipment and Automation.
Advancements in coating machinery have made the process more efficient, precise, and scalable.
High-Efficiency Coating Systems: Machines with better spray distribution and airflow management for uniform coatings.
Automated Process Monitoring: Real-time tracking of key parameters (e.g., thickness, moisture content) using technologies like near-infrared (NIR) spectroscopy.
10. Regulatory Compliance and Quality by Design (QbD)
Pharmaceutical companies are adopting QbD principles to ensure regulatory compliance and consistent quality in coated products.
Process Analytical Technology (PAT): In-line monitoring and control of coating processes to meet strict regulatory standards.
Focus on Patient Safety: Coatings are designed to minimize excipient-related side effects and allergen risks.
CONCLUSION
Recent trends in tablet coating technology focus on innovation, patient-centeredness, and sustainability. From functional coatings for controlled release to solvent-free technologies and smart systems, these improvements are reshaping the pharmaceutical industry. The integration of digital tools and personalized approaches further emphasizes the shift toward modern, efficient, and patient-focused drug delivery systems. Tablet coating technologies have seen significant progress, evolving from basic methods to advanced systems designed to meet the varied needs of modern pharmaceutical formulations. These coatings are essential for improving the therapeutic effectiveness, stability, and patient acceptance of oral dosage forms. In addition to their protective and aesthetic roles, they now facilitate precise drug delivery systems, such as controlled release, delayed release, and targeted delivery, which greatly enhance treatment outcomes and patient compliance.
Recent innovations, such as stimuli-responsive coatings, Nano coatings, and 3D-printed personalized coatings, demonstrate the industry's shift toward precision medicine and advanced drug delivery strategies. Solvent-free technologies, including dry powder coating and hot-melt coating, reflect the increasing emphasis on environmental sustainability and regulatory compliance. Additionally, the integration of continuous manufacturing processes and real-time monitoring technologies ensures improved efficiency, scalability, and consistent product quality. The adoption of patient-centric approaches, particularly in taste masking and the development of easy-to-swallow formulations, further enhances the role of coatings in addressing the needs of specific populations, such as pediatric and geriatric patients. Smart coatings with embedded digital tools offer exciting potential in monitoring adherence and personalizing therapy.
As the pharmaceutical landscape evolves, tablet coating technologies will continue to advance, leveraging novel materials, sustainable processes, and cutting-edge automation. These developments will not only enable cost-effective production but also ensure that future drug formulations are better equipped to meet the demands of both patients and healthcare systems. By balancing innovation with sustainability, tablet coatings will remain a cornerstone of pharmaceutical excellence, driving progress in modern drug delivery systems.
REFERENCES
Hemant Kumar Singh, Kumar Sanbhav Singh, Comprehensive Review Status: Tablets Coating Compositions & Advantage, Int. J. of Pharm. Sci., 2025, Vol 3, Issue 7, 2560-2566. https://doi.org/10.5281/zenodo.16088553
10.5281/zenodo.16088553
