Final answer:
The adverse effect of clonidine is dry mouth.
Step-by-step explanation:
The adverse effect of clonidine is dry mouth. Clonidine is a medication used to treat hypertension and anxiety. It is classified as an alpha-2 adrenergic agonist and works to lower blood pressure by stimulating alpha receptors in the brain, which results in a decrease in sympathetic outflow, leading to decreased peripheral vascular resistance and decreased heart rate.