Background: According to published data, the ability to prevent various hypertension related events differs between the various anti-hypertensive drug groups. Although absolute drug effects with similar drugs also differ among the various studies, relative drug effects could be considered constant. We therefore explored the possibility of drawing statistically valid conclusions about the differences between various drug groups by doing an overview of published data.
Methods: We performed a meta-analysis using a Bayesian fixed effect model in which we brought together 27 published studies. We chose to always relate the drug effects to the number of events observed with placebo drugs. We therefore obtained results both from studies reporting the effects of the newer drugs when tested against diuretics and beta-blockers, and from studies in which diuretics and beta-blockers had been tested against placebo. We constructed the posterior probability distributions of the relative effects of ACE-inhibitors versus calcium antagonists with three different endpoints: stroke, coronary disease and heart failure. We then calculated point estimates of effects with 95% credibility intervals. As an intermediate step in this procedure we obtained similar information about the effects of the three groups of active drugs, ACE-inhibitors, calcium antagonists and diuretics or beta-blockers, tested against placebo.
Findings: ACE-inhibitors and calcium antagonists have an almost identical ability to prevent stroke in hypertensive individuals with a risk ratio (RR) of 1.04. On the other hand, calcium antagonists reduce coronary disease by only 9% relative to placebo. When ACE-inhibitors and calcium antagonists are compared by the Bayesian method, the outcome is a 14% difference in favour of the ACE-inhibitors to prevent coronary disease, with a credibility interval reaching identity. Nor do calcium antagonists do as well as diuretics or _-blockers in this respect, RR = 1.11 with 95% credibility interval 1.01 to 1.22. All the tested drug groups have a profound preventive effect on the occurrence of heart failure when given to hypertensive patients, showing reductions of 44% to 56%. When ACE-inhibitors are compared with calcium antagonists the risk ratio is 0.79, with a credibility interval 0.65 to 0.95.
Interpretation: The conclusion of our analysis is a statistically significant difference between ACE-inhibitors and calcium antagonists in respect of effects on coronary disease and heart failure when treating hypertensive individuals, ACE-inhibitors being more efficacious. The difference is modest and both drug groups are acceptable as first line treatments together with diuretics and beta-blockers. There are no differences in the effect on stroke