The paper studies the strength and disintegration time of compacts made from directly compressible Starch 1500 and its mixtures with directly compressible lactose Pharmatosa DCL 15 in different relative proportions in dependence on the added lubricant magnesium stearate and the model active ingredient ascorbic acid. The dry binders under study differ in their mechanisms of compression and thus in their sensitivity to the addition of the lubricant, which is manifested in decreased strengths of the compacts as well as the mechanism of disintegration of the compacts. The mixtures of substances under study were in the relative representations of 1:3, 1:1 and 3:1. The employed concentration of the lubricant magnesium stearate was 0.4%, that of ascorbic acid, 50%. The study has confirmed and quantitatively evaluated the sensitivity of directly compressible starch to the addition of magnesium stearate. A higher share of directly compressible lactose in the mixture decreased the sensitivity of tableting material to the addition of the lubricant and shortened disintegration time. The presence of stearate did not negatively influence disintegration time, with an exception of the mixture of Starch 1500 and Pharmatosa DCL 15 1:3. An addition of the model active ingredient ascorbic acid decreased the strength of the compacts and shortened the disintegration time in all tableting materials tested.

        Key words: Starch 1500 – Pharmatosa DCL 15 – magnesium stearate – ascorbic acid – tensile strength of tablets – disintegration time of tablets