YIIARMACEUTICA ACTA HELVETIAE EISEVIER Pharmaceutics Acta Helvetiae 70 (1995) 329-337 Compactibility of ternary mixtures of pharmaceutical powders S. Castillo, L. Villafuerte * Escuela National de Ciencias Biolbgicas, Carpio y Plan de Ayala, Col. Santa Tomas, C.P. 11340, D.F. Santa Tomas, M&co Received 7 March 1995; revised 25 March 1995; accepted 31 March 1995 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSR Abstract The tablet hardness (D) of tablets made of mixtures of microcrystalline cellulose (CM), dicalcium phosphate dihydrate (FC) and sodium lauryl sulfate (US) and formed under a compaction pressure (Z’,) ranging up to 980 MPa has been determined. The compactibility of different mixtures (55) was defined with the maximal tablet hardness reached (D,,) and the slope (n) and intercept (I) of the regression curve, using the equation: ln( - In(1 - D/D,,)) = n In P, + I. The experimental maximal tablet hardness of 11 different proportions of the components of a binary mixture of CM and FC showed a maximum at about 80% of CM. Addition of increasing proportions of LSS caused a decrease of tablet hardness and a decrease in the position of this maximum; the experimental data of D,,, for the CM-FC mixtures, with 2% LSS, showed a maximum at about 50% of CM. The tablet hardness of the mixtures was also dependent on compaction pressure. At high compaction pressures the tablet hardness showed more clearly the characteristics of bonds between particles of different materials, whereas at low compaction pressures it seems to represent just an average of bonds between particles of the same materials. Keywords: Compactibility; Ternary mixtures; Pharmaceutical powders; Tablet hardness and lubricants 1. Introduction Tablets represent the greater part of solid dosage forms in the pharmaceutical market, because of its elegance and convenience in application (Leuenberger et al., 1992). For the production of tablets, the application of sufficient compaction pressure is required to induce plastic flow and/or brittle fracture of the primary granules or particles. The compaction conditions at which the plastic flow or the fragmentation of the particles takes effect depends on the physical and chemical properties of the material to be processed (York, 1992 and Wray, 1992). The compaction conditions are defined by the magnitude of the applied force or compaction pressure, the velocity of application of this force and its contact time (Wray, 1992). * Corresponding author. Fax: +52 396 3503 or +52 341 2215. The behavior of pharmaceutical materials during com- paction has been analyzed by means of different tech- niques such as the Heckel equation, force-displacement curves, the energy of compaction and tensile strength and hardness measurements. However, none of them has been found as satisfactory for a comprehensive analysis of the mechanisms involved in the compaction of the solid partic- ulate matter (Celik, 1992). In an article where the effect of the formula composi- tion on their compactibility is mentioned (i.e., Rabasco et al., 1992), it was observed that an increasing proportion of Eudragit @ RL and Eudragit @ RS in formulas based on Eudragit@ L and Eudragit@ R respectively, decreased the hardness of the tablets obtained. It is interesting to notice that at the same time the proportion of Emcompress@ was also reduced. In another article by Pesonen et al., 1992, it was observed that an increasing proportion of cellulose (lo-70%) related to the proportion of Emcompress@ (80- 20%) in a formula, progressively increased the hardness of 0031-6865/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved SsDrOO31-6865(95)00039-9