The main excipients for Direct Compression Formulations

Only three excipients are generally needed:

• Filler-binders serve a double purpose: they impart good flowability to the compression mix and they form robust tablets under normal tableting pressures. These two characteristics take away the need for Wet Granulation which is generally intended to add these two qualities to a compression mix.

• A disintegrant that is effective at relatively low concentrations. For this reason the so-called super-disintegrants are the preferred materials. Unlike traditional starch they work at typical concentrations of 2% to 4%, and at these low levels they do not adversely affect the tableting process.

• Finally a lubricant is almost always essential. By far the most common is magnesium stearate (or calcium stearate), typically used at levels of approximately 0.5%. Many Direct Compression filler-binders and superdisintegrants are very tolerant of the adverse effects caused by overmixing magnesium stearate.

Some cost saving can be made by replacement of some of the SuperTab® lactose by a free flowing grade of sieved Pharmatose® (e.g. Pharmatose® 100M) but beware:

• Pharmatose® does not have the compactability of SuperTab® and
• the deleterious effects of magnesium stearate may become more evident.

Ensure that the SuperTab® concentration remains above about 50% by weight of the tablet formulation. Also take care not to overmix the magnesium stearate, including unintentional overmixing in a rotary feed frame.