Common Enteric Coating Materials: A Procurement Professional’s Guide to Tablet Coating Machines Introduction

Introduction

In pharmaceutical and dietary supplement manufacturing, understanding common enteric coating materials is critical—not only for formulation scientists, but also for procurement professionals responsible for equipment selection and process efficiency. Different enteric polymers behave very differently during coating, and their performance is closely tied to the capabilities of your tablet coating machine.

This guide explains the most widely used enteric coating materials, how they dissolve, what solvent systems they require, and—most importantly—how they interact with tablet coating equipment. The goal is to help procurement teams make informed decisions that balance product quality, production stability, regulatory compliance, and long-term operating costs.

What Are Enteric Coatings and Why Do They Matter?

The Basics of Enteric Coating

Enteric coatings are pH-dependent polymer films applied to tablets or capsules to prevent dissolution in the acidic environment of the stomach. Instead, these coatings remain intact until they reach the higher-pH conditions of the small intestine, where they dissolve and release the active pharmaceutical ingredient (API).

This controlled release mechanism is essential for protecting acid-sensitive ingredients, reducing gastric irritation, and achieving targeted intestinal drug delivery. From a manufacturing perspective, enteric coatings also demand precise control over spray rate, drying efficiency, and film formation—placing higher requirements on tablet coating machines.

Why Procurement Should Care

For procurement professionals, enteric coating is not just a formulation choice—it is a manufacturing strategy. The selection of enteric coating materials directly affects coating yield, defect rates, batch consistency, and overall equipment effectiveness (OEE).

A mismatch between coating polymer properties and tablet coating machine capabilities—such as airflow design, spray system precision, or solvent handling—can lead to coating defects, increased waste, and unplanned downtime. That’s why procurement decisions should always evaluate materials and equipment as a complete system.

Top 5 Common Enteric Coating Materials

Cellulose Acetate Phthalate (CAP)

Cellulose Acetate Phthalate (CAP) is one of the earliest and most established enteric coating polymers. It provides excellent resistance to gastric acid and dissolves at pH levels above 6.0, making it suitable for intestinal release applications.

• Widely compatible with standard tablet coating machines

• Cost-effective and well-documented in pharmaceutical use

• Relatively brittle, requiring careful control of spray rate and drying conditions

CAP is often used in conventional coating systems, but it may require plasticizers and precise process tuning to minimize film cracking during coating and handling.

Hydroxypropyl Methylcellulose Phthalate (HPMCP)

HPMCP is a more advanced enteric polymer offering improved flexibility and film integrity. Depending on the grade, it dissolves between pH 5.5 and 6.5, allowing manufacturers to tailor drug release profiles.

• Compatible with aqueous and organic solvent systems

• Produces smooth, uniform films on modern tablet coating machines

• Requires accurate control of coating thickness and inlet air temperature

HPMCP is widely used in facilities equipped with automated or perforated pan coating machines that provide consistent spray distribution and efficient drying.

Polyvinyl Acetate Phthalate (PVAP)

PVAP is valued for its strong acid resistance and excellent film-forming properties. With a dissolution range of pH 5.0–5.5, it allows for slightly earlier intestinal release compared to CAP or HPMCP.

• Suitable for moisture-sensitive formulations

• Performs well in aqueous coating processes

• Higher material cost, often offset by improved coating robustness

PVAP is commonly selected when manufacturers prioritize process safety and environmental compliance while maintaining stable performance on high-efficiency tablet coating equipment.

Methacrylic Acid Copolymers (Eudragit® L and S)

Methacrylic acid copolymers, such as Eudragit® L and Eudragit® S, are widely used in advanced pharmaceutical applications due to their precise pH-dependent solubility.

• Eudragit® L dissolves at pH ≥ 6.0; Eudragit® S at pH ≥ 7.0

• Excellent mechanical strength and flexibility

• Requires tablet coating machines with precise spray control and airflow management

These polymers are typically paired with high-performance or fully automatic coating machines to achieve consistent, reproducible enteric films.

Shellac

Shellac is a natural resin historically used as an enteric coating material. While less common today, it remains relevant for specific niche applications.

• Natural and biodegradable

• Dissolves at pH 7.0 and above

• Highly sensitive to humidity and storage conditions

Shellac requires stable environmental control and is best applied using tablet coating machines capable of maintaining consistent process conditions.

Comparing Enteric Coating Materials: A Quick Reference Table

The table below compares the most commonly used enteric coating materials based on dissolution pH, solvent system, flexibility, cost considerations, and tablet coating machine compatibility—key factors procurement teams evaluate during equipment and material selection.

Key Considerations When Procuring Enteric Coating Materials

• Compatibility with your tablet coating machine is essential—some polymers require specific spray nozzles, airflow patterns, or drying profiles.

• The solvent system impacts operator safety, environmental compliance, and operating costs.

• Film flexibility and mechanical strength influence tablet durability during packaging and transport.

• Cost should be evaluated alongside coating efficiency and long-term production stability.

• Regulatory compliance and supplier technical support are critical for smooth audits and reliable manufacturing.

Real-World Case Studies: Lessons from the Field

A mid-sized supplement manufacturer switched from CAP to HPMCP to reduce tablet chipping during packaging. The improved flexibility of HPMCP significantly lowered defect rates, but the change required recalibration of their tablet coating machine, particularly drying temperature and spray rate. The result was higher yield and improved batch consistency.

In another case, a pharmaceutical manufacturer selected Eudragit® polymers to achieve targeted drug release in the lower intestine. This required upgrading to coating equipment with enhanced spray control. Although the initial investment was higher, the outcome was a premium product with improved bioavailability—demonstrating the importance of evaluating coating materials and tablet coating machines as an integrated system.

Where to Find Reliable Enteric Coating Materials

When sourcing enteric coating polymers, procurement teams should prioritize suppliers with proven pharmaceutical experience, regulatory certifications, and strong technical support. Reliable suppliers often assist with formulation guidance and process optimization to ensure compatibility with specific tablet coating machines. Authoritative references such as the FDA pharmaceutical excipient database can also support informed decision-making.

Conclusion

Choosing the right common enteric coating materials is not simply a formulation decision—it is a strategic manufacturing choice that directly affects how your tablet coating machine performs in real production environments. Aligning polymer properties with equipment capabilities helps reduce risk, improve efficiency, and ensure consistent product quality.

At JIANPAI, we work closely with pharmaceutical and supplement manufacturers to ensure tablet coating machines are optimized for a wide range of enteric coating materials and process requirements. Evaluating materials and equipment together is the key to building a stable, scalable coating operation.

Frequently Asked Questions (FAQ)

Q1: What is the main difference between CAP and HPMCP?
CAP offers strong acid resistance but tends to be brittle. HPMCP provides greater flexibility and broader solvent compatibility, making it better suited for modern tablet coating machines.

Q2: Can I use the same tablet coating machine for all enteric materials?
Not always. Different polymers may require specific spray systems, drying temperatures, or solvent handling capabilities.

Q3: Are aqueous coatings safer than organic solvent-based coatings?
Generally yes, as they reduce flammability and environmental risks, though some enteric polymers still require organic solvents.

Q4: How does enteric coating affect tablet shelf life?
Proper enteric coatings protect APIs from moisture and gastric acid, often extending shelf life and improving stability.

Q5: What should I look for in an enteric coating material supplier?
Look for certifications, consistent quality, technical support, and proven experience with pharmaceutical tablet coating applications.