Interparticle forces in binary and ternary ordered powder mixes.

An ultracentrifuge technique, previously described by Staniforth et al (1981), has been used to study the adhesion profiles of several binary and ternary ordered powder mixes of pharmaceutical interest. The adhesion profile of an ordered mix provides information about the proportion of drug powder adhering with different forces of attraction to the carrier excipient particle surface. The excipient particle size is shown to affect adhesion between the components of a binary ordered mix-recrystallized lactose formed more stable ordered mixes with drug powder when the carrier particle size was increased. Changes in the adhesion profile of each binary system on adding three different fine-powder excipients to form a ternary ordered mix are also examined. The physical properties of carrier particles and the charge interactions of a third powder component with previously formed binary ordered mixes, are found to influence the physical stability of ternary ordered mixes.