Which of the following is not a common side effect of calcium channel blockers such as amlodipine?

• A. Insomnia
• B. Dizziness
• C. Headache
• D. Ankle edema

Answer: (A)

Calcium channel blockers like amlodipine work mainly by relaxing arterial smooth muscle, causing vasodilation. This vasodilation lowers blood pressure but can lead to side effects tied to that mechanism: dizziness and headache from reduced vascular resistance and cerebral vasodilation, and ankle edema from increased capillary hydrostatic pressure in the limbs. Insomnia isn’t connected to the vasodilatory effects of these drugs, so it’s not a common side effect.