Final answer:
The client taking metoprolol for hypertension should be directed to report bradycardia as this is a specific adverse effect of beta blockers like metoprolol. Dry cough, headache, and muscle weakness are less specific to metoprolol's adverse effects.
Step-by-step explanation:
A nurse should instruct a client who is newly diagnosed with hypertension and is taking metoprolol to report bradycardia as an adverse effect of this medication. Metoprolol is a beta blocker that works by blocking beta-1 receptors, which can slow heart rate (HR) as a method to treat hypertension. However, overprescription or heightened sensitivity to these drugs may lead to a dangerously slow heart rate, known as bradycardia, and could potentially result in the stoppage of the heart.
Among the other listed manifestations, dry cough, headache, and muscle weakness are less specific to the adverse effects of metoprolol, and while they might be of concern in different contexts, they are not typically associated with beta blocker therapy. It's important for the client to know bradycardia as it is directly relevant to the action of metoprolol on the cardiovascular system.