Identification and Prevention of Insoluble Reaction Products Forming after Dissolution of Effervescent Multi-Vitamin Tablets

Abstract Two problems of an unacceptable nature were experienced during the formulation of effervescent multi-vitamin and mineral tablets. When tablets containing ascorbic acid, calcium carbonate and vitamins, combined with ordinary effervescent excipients and sodium benzoate as lubricant, were dissolved, fine needles formed during effervescence. These needles float on top of the solution, making the product unattractive. During effervescence of a second tablet containing magnesium oxide and calcium carbonate, combined with ascorbic acid, a flake-like sediment formed. Infrared spectrophotometry, differential scanning calorimetry and atomic absorption analysis showed that the needles were benzoic acid, while the flakes were citrates - mainly calcium citrate. These problems were overcome by substituting the benzoic acid with micronised polyethylene glycol 6000 and by not including citric acid during the granulation stage but to add coarse citric acid crystals to the dry granules - composed of the rest of the tablet ingredients.