The nurse is explaining the differences between uncontrolled and controlled substances.
Which of the following medications is a controlled substance?

Choice A rationale

Metoprolol is a beta-blocker used to manage hypertension and other cardiovascular conditions, but it is not a vasodilator used for hypertensive crises.

Choice B rationale

Metformin is an oral hypoglycemic agent used to manage type 2 diabetes and has no role in treating hypertension or hypertensive crises.

Choice C rationale

Lisinopril is an angiotensin-converting enzyme (ACE) inhibitor used to manage hypertension and heart failure, but it is not typically used for hypertensive crises.

Choice D rationale

Nitroglycerin is a potent vasodilator used to rapidly lower blood pressure in hypertensive crises. It works by dilating blood vessels, thus reducing blood pressure effectively. .

Choice A rationale

Azithromycin can prolong the QT interval, leading to potential cardiac arrhythmias. Patients with a history of prolonged QT interval or other heart conditions should be monitored closely.

Choice B rationale

Constipation is not commonly associated with azithromycin use. Gastrointestinal side effects may include diarrhea or nausea but not constipation.

Choice C rationale

While tachycardia can be a side effect of some medications, azithromycin is more commonly associated with QT prolongation rather than causing increased heart rate directly.

Choice D rationale

Hyperkalemia is not typically a concern with azithromycin. Electrolyte imbalances are not a common side effect of this antibiotic.