EVALUATION OF THE POISSON-DISTRIBUTION FOR ESTIMATING THE QUALITY OF DRUG DILUENT RANDOM POWDER MIXTURES .1. HIGH PARTICLE-SIZE OF THE DRUGCONSTITUENT

Use of the Poisson distribution to estimate the quality of random mixt ures was evaluated as a measure of the highest attainable degree of do se uniformity of tablets. Ingredient A was assumed to have a large par ticle size as compared to diluent B. In contrast to the more precise b inomial distribution, for the simple Poisson approach no experiments a re necessary to investigate the mean proportions of the apparent volum e, a(v) and b(v) which A and B assume within the powder samples in the die. The range of volume ratios was defined where the Poisson distrib ution is valid. Accepting an error of 5% of the random content variati on of A per sample, a(v) may amount to up to 0.1 (10%). In terms of th e proportion by mass of A, a, this range is wider, and commonly of the order of 0.2 or higher. This approach was tested with tablets prepare d from mixtures of coarse sucrose A and a fine Avicel/talc diluent B a t A:B (m:m) ratios from 10:90 to 50:50. Even with the 30:70 tablets, t he variations of the sucrose content were still in good agreement with the content variations of the random mixtures as estimated from the P oisson distribution. Estimates of the 50:50 ratio, however, deviated f rom the Poisson distribution.