Clarinex and Claritin are very similar, second generation antihistamine medications used for the treatment of allergies. In fact, Clarinex (desloratadine) is the active metabolite of Claritin (loratadine). When Claritin is taken by mouth, our body metabolizes most of the drug to Clarinex.
Although it doesn't seem as though simply dosing the active metabolite of a drug would result in better efficacy, there are some attributes of Clarinex that may work it's favor.
- Clarinex has a longer half-life than Claritin meaning that is lasts in the body for a longer period of time. It is not known if this translates to a longer duration of action however.
- Clarinex has a higher potency for the histamine receptor than Claritin. Studies show the potency is 10-20 times greater. It is unknown if this results in greater efficacy in comparison to Claritin.
Due to the significant cost of Clarinex vs. Claritin, it is a seldom used drug. Most studies conclude there is no significant difference in effectiveness versus other second generation antihistamines such as Claritin and Zyrtec. In addition, Clarinex is still available only via prescription whereas Claritin is available over the counter.
Having said all that, if you have been on a second generation antihistamine such as Claritin and it isn't working well enough, Clarinex may be an option to try. A recent study in 2010 found that participants rated Clarinex as more effective than other treatments with a faster onset of action.