Non-effervescent pharmaceutical compositions having at least one particle of carbonate coated by a layer of polyethylene glycol that substantially covers the at least one carbonate particle are described. Compositions are also described where the compositions include a weakly basic therapeutic agent, a first pH-modifying agent having at least one particle of carbonate coated by a layer of polyethylene glycol, and a second pH-modifying agent. The weakly basic therapeutic agent could be, but is not limited to, zolpidem or scopolamine. Compositions including zolpidem and scopolamine are used to treat insomnia and depression, respectively.
