Potassium carbonate as a desiccant in effervescent tablets

Abstract

A central composite study design was used to determine the moisture scavenging effect of 0–2% w/w potassium carbonate in an effervescent dosage form containing 0.2–1.3% w/w total moisture. Total moisture content of the tablets was calculated by adding the water contribution of each ingredient based on loss on drying or Karl Fischer data. Tablets were directly compressed on a rotary tablet press, packaged in cold form foil/foil blisters, and then thermally stressed by exposure to 75°C for 3 h. In this study, exposure of effervescence in such a manner has been shown to release water of hydration from dextrose monohydrate, thus giving a convenient means of adding water and then `activating' it to perform rapid moisture stability studies. After thermal stressing, tablets were given a rating from 0–7 (least to most) as to the degree of tablet mottling due to effervescent base degradation. Response surface regression of the data resulted in a quadratic equation with an adjusted R2 of 0.92 and no evidence of lack of fit (P=0.85). Analysis of the data showed the optimal level of potassium carbonate to be 1.3% w/w for the formulations tested. This level of potassium carbonate will accommodate total moisture levels up to 0.4% w/w and still prevent effervescent base degradation.