Nonuniform Drying
Causes: Remedies
- Poor air circulation (tray dryer): Have oven air circulation checked and corrected
- Dryer overload:
- Reduce the number of trays.
- Reduce the thickness of wet mass on the trays (tray load).
- Try a fluid bed dryer.
Granule case hardening (hard crust forms with incomplete drying inside granule)
Causes: Remedies
- Too rapid evaporation of water / Oven drying conditions too efficient:
- Try recirculating oven air (damper closed) for an initial 15 to 30 minutes, then open the damper partially for a short period, and finally open the damper fully.
- Reduce drying temperature
- Add Avicel PH-101 to formulation (gives more even water evaporation and uniform granule moisture content).
- Use a fluid bed dryer
Color Migration
Causes: Remedies
- Colors migrate to granule surfaces (wet granulation); tablets have a mottled appearance:
- Use lakes instead of soluble dyes (will minimize but not eliminate).
- Decrease the size of the wet granules
- Decrease the thickness of the granulation bed; stir the granulation bed frequently during drying to expose fresh surfaces at the top of the wet mass
- Use Avicel PH-101- reduces or eliminates dye migration in wet granulation.
Drug Migration
Causes: Remedies
- Drug migrates to granule surfaces; content uniformity problems may result as the drug becomes part of “fines” after dry screening or there is a loss of drug with subsequent low tablet assays
- Use lakes instead of soluble dyes (will minimize but not eliminate).
- Decrease the size of the wet granules
- Decrease the thickness of the granulation bed; stir the granulation bed frequently during drying to expose fresh surfaces at the top of the wet mass
- Use Avicel PH-101- reduces or eliminates dye migration in wet granulation.
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