Nifedipine is classified as which type of medication, and what precaution should be observed before administering it?

• A. Beta-adrenergic blocker used for tachyarrhythmias; monitor for bronchospasm
• B. ACE inhibitor used for heart failure; monitor for hyperkalemia
• C. Thiazide diuretic used for edema; monitor for dehydration
• D. Calcium channel blocker antihypertensive; do not give if blood pressure is low

Answer: (D)

Nifedipine is a calcium channel blocker, specifically in the dihydropyridine class, whose main effect is to relax vascular smooth muscle and lower blood pressure. Because it lowers blood pressure, the key precaution before giving it is to assess the patient’s BP and withhold the dose if the blood pressure is too low. Administering it when hypotensive can lead to dangerous drops in perfusion to vital organs. This safety check is the primary reason for the correct answer.

Understanding the context helps: beta-blockers, ACE inhibitors, and thiazide diuretics are different drug classes with distinct primary actions and cautions, so they are not the appropriate labeling or precaution for nifedipine. The important point with nifedipine is its vasodilating effect and the need to verify adequate blood pressure before administration.