The formation of lactose plugs for hard shell capsule fills

The purpose of this investigation was to study the effects of lubricant concentration, dosator pressure, and dosator piston height on the properties of lactose plugs. An apparatus designed to simulate Macofar 13/2 capsule filling equipment was used, and the relationship between the variables and the responses was established using a Box-Behnken three-factor, three-level experimental design followed by multiple regression. Plug porosity, both under compression and after ejection, was found to be dependent on dosator pressure. Plug weight and length were dependent on dosator piston height, and uniformity of plug weight was independent of all the factors studied. Plug ejection pressure was dependent on dosator pressure and dosator piston height, even when ejection pressure was corrected for changes in plug length. Lubricant concentration had no significant effect on any plug property, and it must be concluded that 0.5% magnesium stearate provides adequate lubrication for lactose plugs. No interaction between variables was noted, and values of the variables raised to the power 2 had no significant effect, permitting a simplified experimental design to be adopted for future work.