The present invention provides for a storage stable pharmaceutical liquidsolution for oral administration having a pharmaceutically effective amount ofan antihistamine and having a purity equal to or greater than about 99% byweight-based HPLC assay, residual solvents of less than about 0.5%, and atotal impurity of less than about 0.2%. The storage stable solution preferablycontains cetirizine. The present invention further provides a process ofpreparing the storage stable pharmaceutical liquid solution as well as amethod of treating a mammal with a therapeutically effective amount ofcetirizine in the stable pharmaceutical liquid solution.
