Press coating is a method used primarily in the pharmaceutical and food industries to create a protective layer around a tablet or other solid dosage forms. The process involves the application of a coating material to the surface of a pre-formed core tablet. Here’s how it works:


  1. Preparation of Core Tablets: Core tablets, which contain the active pharmaceutical ingredient (API) along with excipients, are first prepared. These tablets can be immediate-release or controlled-release formulations.

  2. Coating Process: The core tablets are then placed in a press-coating machine. In this machine, a layer of coating material is pressed onto the surface of the core tablet using mechanical force. The coating material can be in powder form or as a solution.

  3. Types of Coating Materials: The coating materials can vary based on the desired properties, including sugars, polymers, or other substances that provide specific functionalities such as taste masking, delayed-release, or protection from environmental factors.

  4. Benefits: This method allows for precise control over the thickness and uniformity of the coating. It is especially useful for applications requiring multi particulate systems or for producing controlled-release formulations.

Enteric Coating:

Enteric coating is a specialized technique used to apply a protective layer to tablets or capsules that prevents their dissolution in the acidic environment of the stomach but allows for their release in the more neutral pH of the intestine. Here’s an overview:

  1. Purpose of Enteric Coating: The primary goal is to protect sensitive APIs from degradation due to stomach acid and to prevent irritation of the gastric mucosa. It can also enhance the bioavailability of certain drugs by ensuring they reach the intestine before dissolving.

  2. Coating Materials: Enteric coatings are typically made from polymers that are insoluble in acidic conditions but soluble at higher pH levels. Common materials include cellulose acetate phthalate (CAP), methacrylic acid copolymers, and polyvinyl acetate phthalate (PVAP).

  3. Coating Process: The coating can be applied using various methods, including:

    • Spray Coating: The coating solution is sprayed onto the tablet or capsule surfaces in a coating pan or fluidized bed.
    • Dip Coating: Tablets are dipped in a coating solution and then dried.
    • Fluidized Bed Coating: Tablets are suspended in a stream of air and sprayed with the coating solution.

  4. Considerations: The thickness and uniformity of the coating are critical for ensuring the desired release profile. The process also requires careful control of environmental conditions such as temperature and humidity.

  5. Applications: Enteric-coated formulations are commonly used for drugs that are unstable in acidic environments (e.g., certain antibiotics), those that can cause stomach irritation, and medications that are better absorbed in the intestine.

Both press coating and enteric coating are essential techniques in pharmaceutical formulation, offering various benefits that enhance drug delivery and efficacy.