A 56-year-old man started on amlodipine reports a side effect 3 weeks into treatment. Which is the most likely?

• A. Headache
• B. Dizziness
• C. Swollen ankles
• D. Nausea

Answer: (C)

Peripheral edema is a well-known adverse effect of amlodipine, a dihydropyridine calcium channel blocker. It occurs because arteriolar dilation increases capillary hydrostatic pressure, promoting fluid leakage into the interstitial space. This tends to show up after a few weeks of treatment and commonly presents as swelling in the ankles and feet, which fits the scenario of symptoms appearing around three weeks after starting therapy. Headache and dizziness can occur with calcium channel blockers but are less specifically linked and often less persistent, while nausea is less typical. Therefore, swollen ankles best explain the side effect described.