Divergent vasodilator action of calcium antagonists on efferent arterioles. Based on the relative activity on efferent vs. afferent arterioles, calcium antagonists are classified into 3 groups. The first group of calcium antagonists (e.g., nifedipine) elicits predominant vasodilation of afferent arterioles, with modest action on efferent and efferent arterioles. The second group (e.g., nilvadipine) produces both afferent and efferent arteriolar vasodilation, although the efferent arteriolar vasodilation is less than that on the afferent arteriole. The third group of calcium antagonists (e.g., efonidipine) potently relaxes both afferent and efferent arterioles, with nearly the same activity on these vessels. *p < 0.05 vs. baseline. ? = Not examined. From Hayashi et al. [106] with modifications.