**Question:** Prodrug of cetrizine is -

A. Levocetirizine
B. Desloratadine
C. Fexofenadine
D. Cetirizine

**Core Concept:** Prodrugs are biologically inactive compounds that are designed to be converted into their active form(s) within the body.

**Why the Correct Answer is Right:** Levocetirizine is a prodrug of cetirizine, a widely used antihistamine medication. When levocetirizine is taken orally, it is rapidly converted into its active form, cetirizine, through enzymatic hydrolysis in the gastrointestinal tract. Cetirizine is a potent H1-receptor antagonist, blocking the action of histamine and reducing symptoms of allergic reactions.

**Why Each Wrong Option is Incorrect:**

A. Desloratadine (Option B) is another antihistamine drug, but it is not a prodrug of cetirizine. Desloratadine is an active antihistamine drug itself, acting directly on H1-receptors.

B. Fexofenadine (Option C) is another antihistamine drug, but it is not a prodrug of cetirizine. Fexofenadine is an active antihistamine drug itself, acting directly on H1-receptors.

C. Cetirizine (Option D) is the active form of levocetirizine, which is a prodrug. The correct answer is levocetirizine, not cetirizine.

**Clinical Pearl:** Prodrugs like levocetirizine provide a controlled release of drugs, minimizing side effects and improving patient compliance. By using a prodrug, the drug manufacturer has taken advantage of the body's natural processes to deliver the active medication, thereby enhancing drug efficacy and safety.