Sugar, Film & Enteric Coating on Tablets

Sugar Coating:

 Sugar coating is a traditional method of tablet coating that involves applying multiple layers of sugar-based solutions onto tablets to create an elegant appearance, mask the taste and odor of the tablet core, and provide a glossy finish. Here's a detailed explanation of the various steps involved in the sugar coating process for pharmaceutical tablets:

• Step 1: Tablet Core Preparation: The tablets to be coated are first manufactured, typically using compression machines. The tablet core contains the active pharmaceutical ingredient (API) along with other excipients that contribute to the formulation.
• Step 2: Subcoating: In this initial step, a thin layer of a sugar-based solution is applied to the tablet core to provide adhesion for subsequent coating layers. The subcoating solution typically contains sugar (sucrose) and water. The tablets are tumbled or rotated in a coating pan while the solution is sprayed onto them. The subcoating helps create a smooth foundation for the subsequent layers.
• Step 3: Smoothing: To achieve a polished surface for the final coating layers, a smoothing solution is applied. The smoothing solution also contains sugar and water. This step further evens out the tablet surface and prepares it for the final layers.
• Step 4: Color and Flavour Layers (Optional): Intermediate layers of colored and flavored solutions can be applied to enhance the tablet's appearance and taste. These layers involve adding colorants and flavors to the sugar-based solutions. This step can be repeated multiple times to achieve the desired color and flavor.
• Step 5: Final Coating: The tablets are coated with the final sugar-based solution to create the glossy and protective outer layer. This solution contains a higher concentration of sugar and may include polishing agents such as beeswax. The tablets are rotated or tumbled while the solution is sprayed onto them.
• Step 6: Drying: After each coating layer is applied, the tablets are dried to evaporate the water content from the sugar-based solutions. Drying is typically achieved using hot air ovens or other drying equipment. The drying process hardens the sugar layers and prevents the tablets from sticking together.
• Step 7: Polishing (Optional): After the final coating layer is applied and dried, the tablets may undergo a polishing step to enhance the glossy appearance of the coating. Polishing agents like carnauba wax can be used to achieve the desired finish.
• Step 8: Inspection and Packaging: The coated tablets are inspected for uniformity, appearance, and quality. Tablets that meet the specifications are then packaged for distribution. The sugar-coated tablets are often packed in blister packs or bottles for protection and convenience.
• It's important to note that sugar coating is a labor-intensive process that requires several layers and drying steps. While it was once a popular method, modern pharmaceutical manufacturing has shifted toward more efficient and precise coating techniques, such as film coating and fluidized bed coating, which offer benefits in terms of uniformity, efficiency, and versatility.

 Film Coating:

• Film coating is a widely used method for coating pharmaceutical tablets, providing a thin and uniform layer of polymer-based material onto the tablet surface. This coating enhances drug stability, appearance, and patient acceptability. Here's a detailed explanation of the various steps involved in the film coating process for pharmaceutical tablets:
• Step 1: Tablet Core Preparation: Tablet cores containing the active pharmaceutical ingredient (API) and other excipients are prepared using compression machines. The cores are usually uniform in size and shape.
• Step 2: Mixing Coating Solution: The coating solution is prepared by mixing the polymer(s), plasticizer, colorants, and other excipients in appropriate proportions. The solution is formulated to ensure uniform coating application and controlled drug release, if needed.
• Step 3: Loading Tablets: The tablet cores are loaded into the coating equipment, such as a coating pan or fluidized bed coater. The equipment is set up with appropriate controls for temperature, airflow, and spraying parameters.
• Step 4: Preheating (Optional): In some cases, the tablet cores may be preheated to improve adhesion and facilitate the initial stage of coating. This step can help reduce the initial moisture content on the tablet surface.
• Step 5: Spraying the Coating Solution: The tablet cores are exposed to the coating solution using a spray system, which can consist of spray guns or nozzles. The solution is sprayed onto the tablet cores while they are in motion, ensuring even distribution of the coating material. The polymer in the solution adheres to the tablet surfaces.
• Step 6: Drying Phase: After each coat of the solution is applied, the tablet cores are subjected to a drying phase. Hot air is typically used to remove the solvent from the coating solution, leaving behind a thin, solid film on the tablet surface. The drying process is carefully controlled to prevent over-drying or insufficient drying.
• Step 7: Repeating the Process: Multiple coating layers may be applied, each followed by a drying phase, to achieve the desired coating thickness and appearance. The number of coats depends on the specific formulation and desired coating characteristics.
• Step 8: Polishing and Final Drying: After the final coat is applied and dried, the tablets may undergo a polishing step to improve the final appearance and glossiness of the coating. The tablets are then subjected to a final drying phase to ensure complete removal of residual solvents.
• Step 9: Cooling and Inspection: The coated tablets are cooled to room temperature before undergoing quality control inspection. Tablets are visually examined for defects, color consistency, uniformity, and overall quality.
• Step 10: Packaging: Coated tablets that pass inspection are packaged in appropriate containers, such as blister packs or bottles. Packaging protects the tablets from moisture, light, and other environmental factors.
• Film coating offers advantages such as precise control over coating thickness, controlled drug release profiles, and improved tablet appearance. It is widely used in modern pharmaceutical manufacturing due to its efficiency and ability to achieve consistent and high-quality results.

Enteric Coating :

• Enteric coating is a specialized tablet coating process used to protect tablets from the acidic environment of the stomach and facilitate drug release in the intestines. This type of coating is commonly employed for drugs that may be degraded or cause irritation in the stomach. Here's a detailed explanation of the various steps involved in the enteric coating process for pharmaceutical tablets:
• Step 1: Tablet Core Preparation: Tablet cores containing the active pharmaceutical ingredient (API) and other excipients are prepared using compression machines. The cores are usually uniform in size and shape.
• Step 2: Mixing Enteric Coating Solution: The enteric coating solution is prepared by mixing polymers that are resistant to stomach acid and dissolve at a higher pH in the intestines. Common enteric polymers include cellulose derivatives and acrylic resins. Plasticizers, colorants, and other excipients are also added to the solution.
• Step 3: Loading Tablets: The tablet cores are loaded into the coating equipment, which is equipped with controls for temperature, airflow, and spraying parameters specific to the enteric coating process.
• Step 4: Spraying the Enteric Coating Solution: The tablet cores are exposed to the enteric coating solution using a spray system, which typically consists of spray guns or nozzles. The solution is sprayed onto the tablet cores while they are in motion, ensuring uniform distribution of the enteric polymer material.
• Step 5: Drying Phase: After each coat of the solution is applied, the tablet cores undergo a drying phase. The drying process is carefully controlled to remove the solvent from the coating solution. This phase ensures the formation of a solid and continuous enteric coating layer.
• Step 6: Repeating the Process: Multiple coating layers may be applied, each followed by a drying phase, to achieve the desired enteric coating thickness and performance. The number of coats depends on the specific formulation and required enteric protection.
• Step 7: Checking Acid Resistance: Enteric-coated tablets are subjected to acid resistance testing to ensure that the coating effectively withstands the acidic environment of the stomach. This testing involves exposing the tablets to an acidic medium for a specified period to simulate stomach conditions.
• Step 8: Packaging: Enteric-coated tablets that pass acid resistance testing and other quality checks are packaged in appropriate containers. Packaging protects the tablets and ensures they maintain their enteric properties until consumption.
• Enteric coating offers the advantage of protecting sensitive drugs from stomach acid and ensuring that drug release occurs in the intestines, where absorption is optimal. The coating process requires careful control of formulation and process parameters to achieve reliable enteric protection and drug delivery.