Optimization of a formulation for direct compression using a simplex lattice design.

In this paper it is demonstrated how the optimum composition of a mixture for direct compression consisting of alpha-lactose monohydrate, roller-dried beta-lactose and microcrystalline cellulose can be found using a systematic optimization technique. The experiments were chosen according to a simplex lattice design. The results of these experiments were used to fit a mathematical model, which then can predict the properties of all possible mixture compositions and enables a graphic representation of these properties in the form of contour plots. At a level of 4% the effect of three disintegrants (sodium starch glycolate, croscarmellose sodium and crospovidone) on the properties of the tablets compressed from these filler-binders, was evaluated by superimposing the contour plots of the different tablet responses. It was found that all the disintegrants used were effective in this combination of filler-binders. In order to evaluate drug dissolution rate an extra experiment with crospovidone as the disintegrant was performed, in which oxazepam was used as a test drug.

Development and optimization of pharmaceutical formulations using a simplex lattice design.

The composition of pharmaceutical formulations is often subject to trial and error. This approach is time consuming and unreliable in finding the best formulation. Optimization by means of an experimental design might be helpful in shortening experimenting time. Such a design with the concomitant mathematical models, reveals effects and interactions of the variables. The independent variables are the different compositions of the mixtures of the chosen ingredients [drug(s) and excipients]. The dependent variables are the properties (responses) of the formulation. When all responses of interest have been expressed in models that describe the response as a function of the composition of the mixture, the models can be combined graphically or mathematically to find a composition satisfying all demands. In this paper an introduction to the use of mixture designs will be given by means of a theoretical part and an example: optimizing a tablet formulation consisting of excipients only.

Improvement by super disintegrants of the properties of tablets containing lactose, prepared by wet granulation.

The crushing strength, disintegration and dissolution properties of tablets, made by wet granulation with lactose as filter, gelatin as binder, potato starch as disintegrant and magnesium stearate as lubricant can be markedly improved when the potato starch (20%) is replaced by a much lower concentration (4%) of an insoluble super disintegrant, such as sodium starch glycolate (Primojel) or crospovidone (Polyplasdone XL). The incorporation of partially water soluble super disintegrants such as low-substituted sodium carboxymethylcellulose (Nymcel, ZSD 16), causing a viscous barrier in the tablets when containing water, is shown to be deleterious for both tablet disintegration and drug release. In contrast to potato starch, the position of the super disintegrants (intragranular, extragranular or equally distributed) had hardly any effect on the tablet properties. The improved properties of the tablets containing insoluble super disintegrants, when compared to tablets with potato starch, are the result of the use of a much lower concentration of disintegrant, but especially of the difference in effect of magnesium stearate on the disintegration capacity of the slightly swelling potato starch and the strongly swelling super disintegrants, respectively. The latter cause, even in the presence of the liquid penetration inhibiting hydrophobic magnesium stearate, a chain reaction of opening of the tablet, starting at the outside and resulting in a fast disintegration.