Dissolving Methacrylic Acid - Methyl Methacrylate Copolymer (Eudragit L100) for Enteric Tablet Coating

Eudragit L100 (Methacrylic Acid - Methyl Methacrylate Copolymer (1:1)) is an anionic polymer used for enteric coating, meaning it is designed to dissolve only in the higher pH environment of the small intestine (above pH 5.5).

Since the powder is insoluble in water and dilute acids, it must be dissolved in an organic solvent system for tablet coating applications.

Standard Method: Organic Solvent Solution

The standard method for dissolving Eudragit L100 powder involves using a suitable organic solvent system:

1. Suitable Solvents:

   • Ethanol (96%)
   • Isopropanol
   • Acetone
   • Mixtures of these (e.g., Isopropanol/Acetone or Ethanol/Acetone).

2. Concentration: The polymer is typically prepared as a 5% to 15% w/w solution, depending on the desired viscosity and coating equipment.

3. Procedure:

   • Slowly add the Eudragit L100 powder to the stirring solvent system.
   • Continue stirring until a clear, homogeneous solution is achieved. This may take several hours.

4. Crucial Additive: Plasticizer

   • A plasticizer is essential to ensure the resulting film is flexible, adheres well, and does not crack or chip upon drying.
   • Common Plasticizers: Triethyl Citrate (TEC), Dibutyl Phthalate (DBP), or Polyethylene Glycol (PEG).
   • Usage Rate: The plasticizer is typically added at 10-20% of the polymer's dry weight.

5. Optional Additives:

   • Anti-tacking/Opacifier: Talc or Titanium Dioxide can be added to prevent the tablets from sticking together during the coating process and to provide opacity.

Alternative Method: Aqueous Dispersion (Neutralization)

While the powder is typically dissolved in organic solvents, it can also be prepared as an aqueous dispersion by neutralization, although this is more complex:

1. The polymer is dispersed in water.
2. A neutralizing agent (e.g., sodium hydroxide or ammonia) is added to raise the pH above 5.5, causing the polymer to swell and disperse/dissolve.
3. This method is less common for the L100 powder form, as the pre-dispersed form (like Eudragit L 30 D-55) is usually preferred for aqueous coating.