Binderless fluidized bed granulation of a type C hygroscopic pharmaceutical powder with prior humidification treatment

Geldart Type C powder is very fine and cohesive and therefore, very difficult to be fluidized or processed. Severe channeling tends to occur as the inter-particle forces cannot be overcome by the air streams. In this industrial process study, humidification is employed prior fluidized bed granulation to convert a Type C powder to Type A, which is less cohesive and can be readily fluidized. This method was applied to granulate a Type C active pharmaceutical ingredient (API) used for asthma treatment. The API was humidified at approx. 71 to 75% relative humidity and temperatures ranging from 21 to 45 °C over durations of 20 to 60 h. Humidification of the sharp edged particles resulted in the rounding and smoothening of surface morphology due to dissolution, re-crystallization and fusion of contact surfaces. The particle size is increased due to agglomeration. Due to moisture sorption, even without a binder, the humidified material can be readily granulated inside a fluidized bed to form sphere-like agglomerates with improved flowability.