Comparing the use of short-acting and long-acting calcium channel blockers in an HMO

One of the questions surrounding the controversy over the risks of MI among hypertensives taking calcium channel blockers (CCBs) is the dosage form, and whether the short-acting form may be more likely than the long- acting to increase the risk of MI. This preliminary study compared HMO members receiving the two dosage forms by sociodemographic and clinical characteristics, and by utilization (hospital, office visits, emergency room, outside of HMO services) prior to and during CCB use. The sampling frame was members with one or more dispensings for a CCB 1990 through 1994. Incident users were those who received one or more CCB dispensings and no cardiovascular disease-related drugs the year prior to their first dispensing of a CCB. CCB users were those who had at least 90 days of continuous CCB use. Short-acting outnumbered long-acting users by eight to one. Few incident users of long-acting CCBs were found. Among incident users, diagnoses and comorbidities were similar. In general, short-acting users appeared to have less risk of exposure to heart-related medications, but similar risks of exposure to non-heart-related drugs and to utilization of the various services during the year prior to first use. The odds of being exposed to heart-related medications and non-heart related medications and use of services during periods of use of CCBs were similar in general, but where differences were observed, the odds of being exposed were less among short- acting users. Users of the two dosage forms in this setting prior to reports questioning the safety of short-acting CCBs were different quantitatively and qualitatively making a retrospective comparative study difficult, perhaps not possible, due to substantial selection bias among users. Further patient selection bias has also undoubtedly occurred subsequent to the reports. The final answer to the relative safety and effectiveness of the different dosage forms of calcium channel blockers is likely to have come from randomized clinical trials.