What is the most likely side effect of Claritin?

The most likely side effect of Claritin, which is an antihistamine commonly used to alleviate allergy symptoms, is xerostomia, or dry mouth. This side effect occurs because antihistamines block acetylcholine, a neurotransmitter involved in the secretion of saliva. As a result, the inhibition of this action can lead to reduced saliva production, causing the sensation of a dry mouth.

Claritin is known for being a second-generation antihistamine, which typically produces fewer sedative effects compared to first-generation antihistamines. Therefore, sedation is less common with Claritin, making it an incorrect choice. Similarly, while some medications and conditions can lead to weight gain, it is not a commonly associated side effect of Claritin. Lastly, hypertension is not a recognized side effect of Claritin; rather, it may occur with certain other medications or conditions. Thus, xerostomia stands out as the primary side effect associated with the use of Claritin.