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Tablet coating problems and remedies

The coating on tablets helps withstand the gastric environment and has many advantages like masking odor, a color, teste of a drug with physical and chemical protection to drugs. Sometimes tablet’s quality may be improper if the proper method and technique are not followed. So to avoid these problems, we use a few techniques to solve this type of coating problem. In this article, we discuss the tablet coating problems and remedies with the solution.

Types of tablet coating problems:

• Blistering

• Cratering

• Picking

• Pitting

• Blooming

• Blushing

• Colour Variation

Tablet coating problems and remedies:

1. Blistering:

Tablet coating problems and remedies

The blistering is the local detachment of film from the surface of tablets.

Reason: This is because of the gases Penetration inside/ underneath the film. It may be due to overheating either during spraying or at the end of the coating process.

The cause and remedies of blistering:

Cause:

  • It is because heating and temperature Affect the plasticity, strength, and adhesion of the film.

Remedies:

  • Use mild heating or temperature condition during the Coating process.

2. Cratering:

Tablet coating problems and remedies

In this defect, volcanic-like craters may appear on the tablet surface.

Reason:

During the coating process, the coating solution penetrates the tablet’s surface, often at the Crown area where the surfaces are more porous, causing localized disintegration of the core and disruption of the coating.

Causes:

  • Inefficient drying.
  • The highest weight of spraying solution or application of coating solution.

Remedies:

  • Decrease spray Rate
  • Use efficient and optimum drying conditions.
  • Increase viscosity of coating solution to decrease spray application rate.

3. Picking/Sticking:

This defect is due to the coating film pulling away from Tablets’ surface when tablets stick together during the coating process.

Tablet coating problems and remedies

Reason:

This condition is similar to cratering that also produces picking due to wet tablets moving inside bad stick together and then breaking apart.

Cause:

  • Inefficient drying
  • Over-wetting due to high spray rate.
  • Low pan speed rate.

Remedies:

  • Use optimized drying conditions for increasing the inlet air temperature.
  • Decrease spray rate of the coating solution
  • Increase viscosity of the Coating solution.
  • Increase pan speed.

4. Pitting:

Tablet coating problems and remedies

Pitting is the defect that occurs on the tablet’s surface without any visible disruption of the film coating.

Pitting is because of the higher temperature of the tablet Core compared to the melting point of the material used in the tablet formulation process.

Related post: Tablet manufacturing defects and remedies

Cause:

  • Inappropriate drying air inlet temperature.

Remedies:

  • It may be due to Dispensed material with preheating procedure at the start of coating and change in the drying (inlet air) temperature. The temperature of the tablet is not greater than the melting point of the material used in the coating process.
  • Control drying temperature.

5. Blooming:

This effect is due to a change in the tablet’s coating color (dull color) after the prolonged storage of tablets at a higher temperature.

Reason:

  • It is due to collection on the surface of the low molecular weight ingredients (plasticizer) included in the coating formulation.

Cause:

  • Blooming may be due to the high concentration and low molecular weight of the plasticizer.
  • Remedies:
  • Decrease the concentration of the plasticizer and the increased molecular weight of the plasticizer.

6. Blushing:

Tablet coating problems and solution

Blushing is the whitelist specks or film haziness.

Reason:

Blushing may be Due to the precipitated polymer provoked by the use of high coating temperature at about the thermal gelation temperature of the polymers.

Cause:

  • High coating temperature
  • The sorbitol in the formulation causes the most significant fall in the thermal gelation temperature of some cellulose like hydroxypropyl cellulose (HPC), hydroxypropyl methylcellulose(HPMC) methylcellulose, and cellulose ethers.

Remedies:

  • This problem can be avoided by a decrease in the drying air temperature.
  • And by avoiding using sorbitol with hydroxypropyl cellulose, hydroxypropyl methylcellulose, methylcellulose, and cellulose ether.

7.Colour Variation:

Tablet coating problems and remedies

This defect involves variation in the color of the film.

Reason:

Change in the frequency and duration of the Tablet appearance in the spray zone or the size/ shape of the spray zone.

Cause:

  • Irregular the Spray pattern
  • Lack of proper coating
  • Improper mixing of materials
  • Color variation may be due to the Migration of the soluble dyes-plasticizer and other additives during the drying process.

Remedies:

  • Do geometric mixing
  • use different plasticizers and additives
  • use a mild drying condition.

images credit- all image credits to sensientpharma.com and screenshot taken by the author.

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