Importance Of Powder Density In Solid Dosage Form

By: Martin A. Thomas Ph.D., Director of Business Development

Both active and inactive (excipient) compounds are used in the manufacture of solid dosage formulations, i.e. tablets and capsules. These powders possess many properties or characteristics and exhibit certain behaviors as a result.

Tapped Density
One important characteristic is tapped bulk density, or simply tapped (tap) density: that is, the maximum packing density of a powder (or blend of powders) achieved under the influence of welldefined, externally applied forces. The minimum packed volume thus achieved depends on a number of factors including particle size distribution, true density, particle shape and cohesiveness due to surface forces including moisture. Therefore, the tap density of a material can be used to predict both its flow properties and its compressibility (see right sidebar as to how). These are just two of the many parameters which are important in the overall tabletting process - which requires that loose powders be compacted into a durable solid form with the correct mechanical strength, porosity and dissolution characteristics – and in capsulefilling performance.