Which of the following is NOT an effect of calcium channel blockers?

Calcium channel blockers primarily function by inhibiting the influx of calcium ions into cardiac and smooth muscle cells, which leads to a variety of cardiovascular effects. Among these effects, decreased heart rate, vasodilation, and reduced blood pressure are all well-known outcomes of calcium channel blockade.

Increased heart rate is typically antagonized by calcium channel blockers, as they have a negative chronotropic effect—this means they lower the heart rate. Vasodilation occurs as these medications relax the smooth muscle in blood vessels, leading to an expanded lumen and decreased vascular resistance. This also contributes to reduced blood pressure, as dilated blood vessels allow blood to flow more easily, which lowers the workload on the heart.

The option of increased cardiac contractility is not consistent with the action of calcium channel blockers. In fact, by blocking calcium channels, these medications reduce the amount of calcium available for muscle contraction in the heart, which diminishes cardiac contractility. Therefore, this effect stands in contrast to the mechanism of action for calcium channel blockers, making it the correct choice to identify as not being an effect of these drugs.