Aim: Film Coating of Tablets/Granules
References
1. Banker, G.S., & Rhodes, C.T. (2002). Modern Pharmaceutics. Marcel Dekker.
2. Lieberman, H.A., Lachman, L., & Schwartz, J.B. (1989). Pharmaceutical Dosage Forms: Tablets. Marcel Dekker.
3. Remington, J.P. (2006). Remington: The Science and Practice of Pharmacy. Lippincott Williams & Wilkins.
Objective
To apply a film coating to prepared tablets or granules and evaluate the quality of the coating in terms of uniformity, appearance, weight gain, and disintegration time.
Materials Required
Core Tablets/Granules: Prepared uncoated tablets or granules
Coating Solution:
Polymer: Hydroxypropyl Methylcellulose (HPMC) or Ethyl Cellulose
Plasticizer: Polyethylene Glycol (PEG) or Glycerin
Colorant: Titanium Dioxide or FD&C approved colorants
Solvent: Purified Water or Ethanol
Opacifier: Talc
Equipment Required: Tablet Coating Pan or Fluidized Bed Coater, Spray Gun or Atomizer, Hot Air Blower, Analytical Balance, Thermometer, Humidity Controller, Polishing Cloth or Powder
Quantities of Ingredients (for 1000 Tablets)
HPMC (5% w/w): 50 g
Plasticizer (PEG 400, 1% w/w): 10 g
Colorant (Titanium Dioxide, 0.5% w/w): 5 g
Opacifier (Talc, 0.5% w/w): 5 g
Solvent (Water or Ethanol): q.s. (quantum satis) to make 1,000 mL of coating solution
Procedure
1. Preparation of Coating Solution:
- Dissolve the required quantity of HPMC in purified water with continuous stirring until a clear solution is formed.
- Add the plasticizer (PEG 400 or Glycerin) to the solution and mix thoroughly.
- Add colorants (e.g., Titanium Dioxide) and opacifiers (e.g., Talc) to the solution and stir until a uniform dispersion is achieved.
- Pass the solution through a fine mesh to remove any undissolved particles.
2. Loading of Tablets/Granules:
- Load the core tablets or granules into the coating pan or fluidized bed coater.
- Set the coating pan to rotate at a moderate speed (10-15 rpm) to ensure uniform exposure of all tablets/granules.
3. Coating Process:
- Start the hot air blower to maintain a drying temperature between 40-60°C.
- Using a spray gun or atomizer, apply the coating solution onto the rotating tablets/granules in a fine mist.
- Adjust the spray rate to ensure a uniform application of the coating solution without causing tablets to stick together.
- Continue the process until the desired thickness of the coating is achieved. Monitor the weight gain of the tablets at regular intervals to assess the amount of coating applied.
4. Drying and Curing:
- Once the desired coating is applied, increase the airflow to dry the tablets/granules completely.
- Allow the coated tablets/granules to cure for 12-24 hours at room temperature to achieve optimal film strength.
5. Polishing (Optional): For aesthetic purposes, polish the coated tablets with a polishing cloth or dust them with a polishing powder to achieve a smooth, shiny surface.
Evaluation of Coated Tablets/Granules
1. Uniformity of Coating: Visually inspect the coated tablets/granules for uniformity of color and absence of defects such as mottling, rough spots, or cracks.
2. Weight Gain: Weigh 20 coated tablets/granules and calculate the average weight gain due to the coating. The percentage weight gain is determined using the formula:
Percentage Weight Gain =
3. Disintegration Time: Perform a disintegration test on six coated tablets using a disintegration test apparatus in distilled water at 37°C.Record the time taken for all tablets to disintegrate completely.
4. Dissolution Test: Conduct a dissolution test using a suitable dissolution medium (e.g., phosphate buffer) at 37°C in a dissolution apparatus.Withdraw samples at regular intervals (5, 10, 15, 30, 45, and 60 minutes) and measure the absorbance using a UV spectrophotometer at the drug’s specific wavelength.
Sample Data Table
| Parameter | Tablet No. 1 | Tablet No. 2 | Tablet No. 3 | Tablet No. 4 | Tablet No. 5 | Tablet No. 6 | Average |
| Initial Weight (mg) | 500 | 502 | 498 | 501 | 499 | 500 | 500 |
| Final Weight (mg) | 510 | 513 | 508 | 512 | 509 | 511 | 510.5 |
| Weight Gain (%) | 2 | 2.2 | 2 | 2.1 | 2 | 2.2 | 2.08 |
| Disintegration Time (min) | 10 | 11 | 9 | 12 | 10 | 11 | 10.5 |
| Dissolution (%) at 60 min | 90 | 91 | 89 | 92 | 90 | 91 | 90.5 |
Conclusion
The film-coated tablets/granules meet the desired specifications for coating uniformity, weight gain, disintegration time, and dissolution profile, indicating successful film coating.