Which of the following is a common adverse drug reaction of Clonidine?

Clonidine is an alpha-2 adrenergic agonist primarily used to treat hypertension and certain pain conditions. One of the common adverse drug reactions associated with Clonidine is dizziness. This outcome can occur due to its central nervous system effects, where the drug reduces sympathetic outflow, leading to decreased blood pressure and a potential resultant state of dizziness or lightheadedness, especially upon standing (orthostatic hypotension).

Other side effects of Clonidine can include sedation and dry mouth, but dizziness is particularly notable because of its direct impact on blood pressure regulation. Monitoring patients for this effect is essential, especially when initiating therapy or adjusting doses.

The other options, while they may be associated with various medications or conditions, are less commonly a direct result of Clonidine use. Hyperkalemia is more commonly associated with medications such as ACE inhibitors or certain diuretics rather than Clonidine, which does not notably affect potassium levels. Diarrhea and constipation can occur with many medications, but they are not specifically recognized as primary adverse effects of Clonidine. Therefore, dizziness stands out as a significant reaction that clinicians should anticipate when prescribing Clonidine.