Current status of calcium antagonists in Japan

Calcium antagonists comprise the most popular drug class for treatment of hypertension in Japan. More than half of Japanese clinicians use calcium antagonists as initial drug treatment for mild-to-moderate hypertension and, despite recent controversies, their use continues to increase. Nearly a fourth of clinicians use angiotensin-converting enzyme (ACE) inhibitors, and 9% use beta-receptor blockers. There are 12 dihydropyridine calcium antagonists and 1 benzothiazepine agent in clinical use. Amlodipine is the most widely used agent in the class. Efonidipine and cilnidipine, recently developed in Japan, both have a slow onset of action and long-lasting hypertensive effect and possess characteristics unique to the class. Efonidipine dilates the efferent as well as the afferent arterioles of the glomerulus; therefore, it appears to have a more pronounced renoprotective effect than other calcium antagonists. Cilnidipine is a dual-channel antagonist, acting on both the peripheral neuronal N-type and vascular L-type calcium channels. It depresses the pressor response to acute cold stress but does not induce tachycardia by hypotensive baroreflex.