POTASSIUM CARBONATE AS A DESICCANT IN EFFERVESCENT TABLETS

A central composite study design was used to determine the moisture sc avenging effect of 0-2% w/w potassium carbonate in an effervescent dos age form containing 0.2-1.3% w/w total moisture. Total moisture conten t of the tablets was calculated by adding the water contribution of ea ch ingredient based on loss on drying or Karl Fischer data. Tablets we re directly compressed on a rotary tablet press, packaged in cold form foil/foil blisters, and then thermally stressed by exposure to 75 deg rees C for 3 h. In this study, exposure of effervescence in such a man ner has been shown to release water of hydration from dextrose monohyd rate, thus giving a convenient means of adding water and then 'activat ing' it to perform rapid moisture stability studies. After thermal str essing, tablets were given a rating from 0-7 (least to most) as to the degree of tablet mottling due to effervescent base degradation. Respo nse surface regression of the data resulted in a quadratic equation wi th an adjusted R-2 Of 0.92 and no evidence of lack of fit (P = 0.85). Analysis of the data showed the optimal level of potassium carbonate t o be 1.3% w/w for the formulations tested. This level of potassium car bonate will accommodate total moisture levels up to 0.4% w/w and still prevent effervescent base degradation. (C) 1997 Elsevier Science B.V.