What is the difference between clarinex and claritin (loratadine)?

Not muck. Clarinex is the active metabolite of claritin, (loratadine) the molecule that is active after Claritin (loratadine) is processed by the liver. The method of action and the active compound is the same.
Structure. Clarinex is one stereo chemical form of the loratidine molecule. It has a longer duration of action, 27 hours, than claritin, (loratadine) and is a truly a once daily medication.