Coated tablets are a form of tablet in which one or more layers of special materials are coated around the active pharmaceutical ingredient (API). Their design aims to improve the appearance, stability, solubility, and medication compliance of the drug. The main components of coated tablets include the drug core, the coating material, and excipients. These components work synergistically to ensure the efficacy and safety of the drug.
1. Drug Core Components
The core of a coated tablet typically consists of the active pharmaceutical ingredient (API) and excipients. The active pharmaceutical ingredient is the key substance that exerts the therapeutic effect, such as antibiotics, antihypertensive drugs, or vitamins. Excipients include fillers (such as starch and microcrystalline cellulose), binders (such as hydroxypropyl methylcellulose), disintegrants (such as croscarmellose sodium), and lubricants (such as magnesium stearate). These components work together to ensure the formation, stability, and in vivo disintegration properties of the drug core.
2. Coating Material
The main function of the coating layer is to protect the drug core and regulate drug release. Commonly used coating materials include:
• Sugar coating: A traditional coating material, primarily composed of sucrose, providing a smooth surface and masking unpleasant drug tastes. However, its preparation process is complex and its moisture resistance is poor.
• Film coating: Modern coated tablets mostly use polymer films, such as hydroxypropyl methylcellulose (HPMC), ethyl cellulose, or acrylic resin. These materials have good film-forming properties, and the drug release rate can be controlled by adjusting the thickness and porosity (e.g., sustained-release or enteric coating).
• Enteric coating: Uses materials such as cellulose acetate phthalate (CAP) or polyacrylic acid resin. It does not dissolve in gastric acid and releases the drug only in the alkaline environment of the intestine. It is suitable for drugs that are highly irritating to the stomach (e.g., enteric-coated aspirin tablets).
3. Auxiliary Additives
Plasticizers (e.g., polyethylene glycol), anti-sticking agents (e.g., talc), and colorants (e.g., titanium dioxide or food coloring) are often added during the coating process to improve the flexibility of the coating, prevent adhesion, and enhance visual identification. The formulation of coated tablets must strictly adhere to pharmacopoeia standards to ensure their safety and functionality. By optimizing coating materials and processes, modern coated tablets not only improve the patient's medication experience but also precisely control drug release, making them an indispensable technology in the pharmaceutical industry.
