IS HYPERTENSION ANOTHER INDICATION FOR CALCIUM ENTRY BLOCKERS?
Their use in angina and arrhythmias may be only scratching the surface The calcium channel entry blockers (calcium antagonists) verapamil and nifedipine are approved by the US FDA only for the treatment of angina, but Dr M.P. Blaustein of the University of Maryland believes that they may be the most logical drugs for treating patients with essential hypertension. These patients have increased intracellular sodium due to inhibition of the cell membrane sodium-potassium pump. This results in a calcium influx into smooth muscle cells, which augments vascular tone. Reducing calcium entry into cells should reduce blood pressure, and clinical trials have indeed shown that this is the case. In European and Japanese studies utilising both maintenance and emergent dosing regimens, nifedipine and verapamil have been found effective in reducing blood pressure and free of serious side effects. Usually the effectiveness of verapamil and nifedipine correlates directly with the severity of pretreatment hypertension. Older patients seem to have a more dramatic hypotensive response to these agents than younger individuals. Calcium entry blockers are often effective in patients with hypertension resistant to {3-blocker therapy. Although calcium entry blockers are widely used in Europe as antihypertensives, physicians are reluctant to use them for this indication in the US, probably due to the lack of clinical trials and experience in that country. Adverse effects associated with long term use of these agents (if any) are unknown. Other investigators have utilised calcium entry blockers as prophylactic agents in disorders characterised by smooth muscle spasm (e.g., asthma, achalasia, migraine, myometrial contractions), but more clinical trials are required before conclusions can be made regarding efficacy and safety for these indications. Journal of the American Medical Association 248: 1285 (17 Sep 1982)
0156-2703/82/1009-0003/0$01.00/0 © ADlS Press lNPHARMA 9 Oct 1082 3
