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A Corn Starch / a-Lactose Monohydrate Compound as a New Directly Compressible Excipient

Karl G. Wagner and Jochen A. Dressler

Department of Pharmaceutical Technology (Prof. Dr. Peter C. Schmidt), Eberhard Karl University, Tübingen (Germany)

The purpose of this study was to compare the tableting properties of a new co-processed excipient for direct compression (StarLac®, in the following briefly called "SL") prepared from 15 % corn starch and 85 % a-lactose monohydrate against a physical mixture of the two components. The co-processed material and the physical mixture alone and in combination with two drugs, ascorbic acid and paracetamol, were tested for their powder and tablet properties, like flowability, crushing strength, friability and disintegration time. Additionally, the compaction properties were investigated recording the ejection force, the ratio of lower to upper compaction force and the upper punch displacement. The Heckel model was further used for analysis.
SL is an compound of excellent flow properties and enhanced compressibility compared to spray-dried a-lactose monohydrate crystals into compound particles increased the starch-related effects of enhances binding capacity and compressibilty (plastic deformation performance) against a physical mixture of corn starch and spray-dried lactose. Additionally, the small starch particles within the physical mixture prevented powder flow, thus 0.3 % of Aerosil 200® had to be added in order to make a comparison of the two filler-binders possible. Ascorbic acid could tableted at all tested proportions up to 70 % together with SL, while sticking prevented the compression of mixtures exceeding 30 % ascorbic acid together with the physical mixture.
Paracetamol was more of a challenge to be tableted together with SL, but at a paracetamol level of 70 % tablets of good crushing strength and friability could be obtained. For paracetamol the physical mixture had advantages of better mechanical tablet properties, especially at paracetamol levels below 70 %. Generally all tablets displayed slight hardening while being stored for 1 week. None of the tableting mixtures needed the addition of disintegrant, while tablets that contained SL exhibited a faster disintegration than tablets containing the physical mixture.

Key words Ascorbic acid · Corn starch · a-Lactose monohydrate · Paracetamol · StarLac® ·
Tablets, direct compression

1) Part 1 see Pharm. Ind. 64, No. 8 , p. 800 (2002).