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. Coating/Drying

These wet spheres (sometimes referred to as "beads" or "beadlets") are then transferred to a coating column where they are coated with a slow-release polymer matrix, then dried. The finished spheres are then tableted or encaplulated. In some cases, the extrudates are dried and tableted without going through a spheronizer.