Dose uniformity and redispersibility of pharmaceutical suspensions. I: Quantification and mechanical modelling of human shaking behaviour.

Precision and uniformity of single doses are required for most dosage forms including suspensions for oral and ophthalmic administration. Therefore, solids forming sediments or aggregates must be distributed homogeneously immediately before use. If settling occurs, leading pharmacopoeias require that suspensions be redispersible by shaking, but a standardised testing procedure for this property is not available. Obviously, such a test will have to be based upon observations of human shaking patterns. We report the results of a study in which human shaking acceleration profiles were measured and the shaking intensity characterised by the area under the frequency spectrum obtained by Fourier transform of the autocorrelation function. We also present a prototype of a mechanical redispersibility tester, which is more flexible and simulates human shaking behaviour more closely than its pneumatic forerunner, which was described earlier.