Which of the following second generation antihistamines requires caution in patients with a creatinine clearance less than 10?

Levocetirizine is the correct answer because it is a second-generation antihistamine that is primarily eliminated through the kidneys. In patients with renal impairment, specifically those with a creatinine clearance of less than 10 mL/min, the risk of accumulation and subsequent side effects increases. Therefore, caution is advised when prescribing levocetirizine to ensure that the drug does not reach toxic levels in the body.

While cetirizine, loratadine, and fexofenadine are also second-generation antihistamines, they have different metabolic pathways and clearance mechanisms. While caution may still be necessary for patients with renal impairment, the specific recommendation for creatinine clearance less than 10 mL/min is particularly important for levocetirizine due to its renal excretion profile. It's crucial to consider renal function when prescribing medications to avoid adverse effects and ensure patient safety.