Preparation of Enteric-Coated Tablets

Introduction to Enteric-Coated Tablets

Enteric-coated tablets are designed to bypass the acidic environment of the stomach and release the medication in the alkaline environment of the small intestine. This coating is essential for drugs that are sensitive to stomach acid or cause gastric irritation. The enteric coating allows for delayed or targeted drug release, protecting the drug from degradation in the stomach and improving its therapeutic efficacy. The preparation of enteric-coated tablets involves several steps, as outlined below:

Step 1: Core Tablet Formulation

The first step in preparing enteric-coated tablets involves the formulation of the core tablet. The core contains the active pharmaceutical ingredient (API) along with various excipients, such as fillers, binders, disintegrants, and lubricants. These excipients contribute to the tablet’s structural integrity, aid in disintegration, and facilitate uniform drug distribution. The core tablet is typically prepared using common tablet manufacturing techniques like direct compression or wet granulation.

Step 2: Enteric Coating Formulation

The enteric coating formulation is prepared separately from the core tablet formulation. The key component of the enteric coating is a polymer that is resistant to stomach acid but dissolves or becomes permeable in the alkaline environment of the small intestine. Commonly used polymers for enteric coatings include cellulose acetate phthalate (CAP), hydroxypropyl methylcellulose phthalate (HPMCP), and methacrylic acid copolymers (Eudragit®).

Step 3: Coating Process

The core tablets are coated with the enteric polymer using a specialized coating process. The coating process can be performed using different techniques, such as:

• Fluid Bed Coating: The core tablets are placed in a fluidized bed, and the enteric coating formulation is sprayed onto the tablets. The process is repeated several times until the desired coating thickness is achieved.
• Pan Coating: The core tablets are placed in a rotating pan, and the enteric coating solution is sprayed onto the tablets while the pan rotates. The tablets are dried between each spraying cycle until the desired coating is obtained.

Step 4: Curing

After the coating process, the enteric-coated tablets undergo curing, which involves subjecting them to controlled temperature and humidity conditions. Curing allows the enteric polymer to become fully insoluble, ensuring that the tablets remain intact during storage and handling and that the drug release is delayed until the tablets reach the small intestine.

Step 5: Quality Control

Throughout the enteric-coated tablet preparation process, stringent quality control measures are applied to ensure the tablets meet the required specifications and regulatory standards. Quality control tests typically include evaluation of coating thickness, uniformity, dissolution rate, and stability.

Conclusion

Enteric-coated tablets offer a valuable solution for protecting drugs from stomach acid and improving their therapeutic effectiveness. The preparation of enteric-coated tablets involves formulating the core tablet with the API and excipients, formulating the enteric coating with a suitable polymer, coating the core tablets with the enteric coating using specialized processes, and curing the tablets to achieve the desired enteric protection. By following strict quality control measures, pharmaceutical manufacturers can produce high-quality enteric-coated tablets that offer delayed or targeted drug release for optimal patient treatment.