Abstract
In the preparation of oral solutions, a mixture of syrup and dry-syrup formulations is often diluted with water in a prescription bottle to a desired volume using a graduated scale on the side of the bottle, by which patients measure each dose. Due to increased viscosity of the suspension mixture and limited solubility of dry-syrup formulations, the amounts of drug components contained in a dose may vary between measurements. In this study, we determined differences in the amounts of drug components in each measured dose of an oral solution containing a dry-syrup formulation prepared with different amounts of diluent. Regarding both dry-syrup and syrup formulations, on increasing the amount of diluent, differences in the amounts of the drug components in measured doses became smaller, while these differences became greater in relation to the viscosity of oral solutions. When an oral mixture was prepared with a small amount of diluent, its drug components were at a high level in the first dose but at a lower level in the last dose from a prescription bottle. These observations demonstrate that it is necessary for dose uniformity to use relatively higher dilutions of oral solutions to achieve an appropriate viscosity.
