The Process: Pharmaceutical Applications

The process of wet extrusion, followed by spheronization, is used to produce a wide variety of engineered, controlled release drugs. These solid dosage forms are mostly in the form of tablets or capsules containing high levels of an Active Pharmaceutical Ingredient (API)

Product characteristics for extrusion and spheronization include:

• Dense pellets
• Smooth coatable pellets
• Narrow particle size distributions, and
• High yield and flowability.

The wet extrusion process can be batch or continuous operation and consists of the following steps:

1. Mixing

The pre-mixed dry ingedients, mostly composed of the API and Avicel, are wetted with water or organic solvent and mixed in a high shear granulator or double planetary mixer to form a homogeneous wet mass suitable for wet extrusion.

2. Extrusion

The wet mass is metered by a special feeder into the extruder where it is continuously formed into cylindrical extrudates of uniform shape and size.

3. Spheronization

The wet extrudates are placed in a spheronizer where a gridded, fast spinning disc, breaks them into smaller particles and rounds them to form spheres.

4. Drying / Coating

The wet pellets are then transferred to a Fluid Bed Dryer in which they are dried and subsequently coated using a Wurster insert (if desired). The finished pellets are then sieved to obtain the desired cut and transferred to the packaging step (encapsulator, tableting machine, sachets, etc.).