Calcium channel blockers in diabetic subjects: innocent at last?

Calcium antagonists are indicted as a potential trigger of a variety of complications spanning from myocardial infarction to bleeding and cancer. Three randomised controlled trials, the MIDAS, the FACET and the ABCD trial, seem to suggest that the risk for myocardial infarction is increased in diabetics on calcium antagonists. These trials in aggregate totalled only 92 cardiovascular events and it is possible that the observed differences were due to random errors. Most of the patients of the ABCD trial discontinued the medication to which they were initially randomised before the end of the study, which raised the possibility of systematic bias. In both the MIDAS and ABCD studies cardiovascular events were secondary end-points and the apparent adverse effects were identified only by subgroup analyses. Furthermore, in both studies, patients in the control groups were being treated with ACE inhibitors. The lack of a placebo group makes it impossible to establish whether the observed effects were due to the harmful influence of calcium antagonism or to the favourable effects of ACE inhibition. New data abstracted from the PIUMA database show that the rate of total cardiovascular and cardiac events did not differ between diabetics on calcium antagonists and diabetics not using these drugs. These new data are in keeping with findings in the HOT study where an impressive degree of cardiac protection was observed in diabetic patients on felodipine.